avoid label variable usage in relooper for forward branches, just use a stack of blocks for them. after this change, only irreducible control flow should cause label variable usage

6 files changed, 962 insertions, 1031 deletions

diff --git a/src/cfg/Relooper.cpp b/src/cfg/Relooper.cpp
index 6488b3d06..cde61df0b 100644
--- a/src/cfg/Relooper.cpp
+++ b/src/cfg/Relooper.cpp
@@ -18,6 +18,7 @@
 
 #include <string.h>
 #include <stdlib.h>
+
 #include <list>
 #include <stack>
 #include <string>
@@ -38,6 +39,59 @@ static void PrintDebug(const char *Format, ...);
 #define DebugDump(x, ...)
 #endif
 
+// Rendering utilities
+
+static wasm::Expression* HandleFollowupMultiples(wasm::Expression* Ret, Shape* Parent, RelooperBuilder& Builder, bool InLoop) {
+  if (!Parent->Next) return Ret;
+
+  auto* Curr = Ret->dynCast<wasm::Block>();
+  if (!Curr || Curr->name.is()) {
+    Curr = Builder.makeBlock(Ret);
+  }
+  // for each multiple after us, we create a block target for breaks to reach
+  while (Parent->Next) {
+    auto* Multiple = Shape::IsMultiple(Parent->Next);
+    if (!Multiple) break;
+    for (auto& iter : Multiple->InnerMap) {
+      int Id = iter.first;
+      Shape* Body = iter.second;
+      Curr->name = Builder.getBlockBreakName(Id);
+      auto* Outer = Builder.makeBlock(Curr);
+      Outer->list.push_back(Body->Render(Builder, InLoop));
+      Outer->finalize(); // TODO: not really necessary
+      Curr = Outer;
+    }
+    Parent->Next = Parent->Next->Next;
+  }
+  // after the multiples is a simple or a loop, in both cases we must hit an entry
+  // block, and so this is the last one we need to take into account now (this
+  // is why we require that loops hit an entry).
+  if (Parent->Next) {
+    auto* Simple = Shape::IsSimple(Parent->Next);
+    if (Simple) {
+      // breaking on the next block's id takes us out, where we
+      // will reach its rendering
+      Curr->name = Builder.getBlockBreakName(Simple->Inner->Id);
+    } else {
+      // add one break target per entry for the loop
+      auto* Loop = Shape::IsLoop(Parent->Next);
+      assert(Loop);
+      assert(Loop->Entries.size() > 0);
+      if (Loop->Entries.size() == 1) {
+        Curr->name = Builder.getBlockBreakName((*Loop->Entries.begin())->Id);
+      } else {
+        for (auto* Entry : Loop->Entries) {
+          Curr->name = Builder.getBlockBreakName(Entry->Id);
+          auto* Outer = Builder.makeBlock(Curr);
+          Outer->finalize(); // TODO: not really necessary
+          Curr = Outer;
+        }
+      }
+    }
+  }
+  return Curr;
+}
+
 // Branch
 
 Branch::Branch(wasm::Expression* ConditionInit, wasm::Expression* CodeInit) : Ancestor(nullptr), Condition(ConditionInit), Code(CodeInit) {}
@@ -53,12 +107,11 @@ wasm::Expression* Branch::Render(RelooperBuilder& Builder, Block *Target, bool S
   auto* Ret = Builder.makeBlock();
   if (Code) Ret->list.push_back(Code);
   if (SetLabel) Ret->list.push_back(Builder.makeSetLabel(Target->Id));
-  if (Ancestor) {
-    if (Type == Break) {
-      Ret->list.push_back(Builder.makeShapeBreak(Ancestor->Id));
-    } else if (Type == Continue) {
-      Ret->list.push_back(Builder.makeShapeContinue(Ancestor->Id));
-    }
+  if (Type == Break) {
+    Ret->list.push_back(Builder.makeBlockBreak(Target->Id));
+  } else if (Type == Continue) {
+    assert(Ancestor);
+    Ret->list.push_back(Builder.makeShapeContinue(Ancestor->Id));
   }
   Ret->finalize();
   return Ret;
@@ -128,7 +181,6 @@ wasm::Expression* Block::Render(RelooperBuilder& Builder, bool InLoop) {
   if (Fused) {
     PrintDebug("Fusing Multiple to Simple\n", 0);
     Parent->Next = Parent->Next->Next;
-
     // When the Multiple has the same number of groups as we have branches,
     // they will all be fused, so it is safe to not set the label at all.
     // If a switch, then we can have multiple branches to the same target
@@ -171,22 +223,21 @@ wasm::Expression* Block::Render(RelooperBuilder& Builder, bool InLoop) {
       }
       bool SetCurrLabel = SetLabel && Target->IsCheckedMultipleEntry;
       bool HasFusedContent = Fused && contains(Fused->InnerMap, Target->Id);
+      if (HasFusedContent) {
+        assert(Details->Type == Branch::Break);
+        Details->Type = Branch::Direct;
+      }
       wasm::Expression* CurrContent = nullptr;
+      bool IsDefault = iter == ProcessedBranchesOut.end();
       if (SetCurrLabel || Details->Type != Branch::Direct || HasFusedContent || Details->Code) {
         CurrContent = Details->Render(Builder, Target, SetCurrLabel);
         if (HasFusedContent) {
           CurrContent = Builder.blockify(CurrContent, Fused->InnerMap.find(Target->Id)->second->Render(Builder, InLoop));
-        } else if (Details->Type == Branch::Nested) {
-          // Nest the parent content here, and remove it from showing up afterwards as Next
-          assert(Parent->Next);
-          CurrContent = Builder.blockify(CurrContent, Parent->Next->Render(Builder, InLoop));
-          Parent->Next = nullptr;
         }
       }
-      bool isDefault = iter == ProcessedBranchesOut.end();
       // If there is nothing to show in this branch, omit the condition
       if (CurrContent) {
-        if (isDefault) {
+        if (IsDefault) {
           wasm::Expression* Now;
           if (RemainingConditions) {
             Now = Builder.makeIf(RemainingConditions, CurrContent);
@@ -217,7 +268,7 @@ wasm::Expression* Block::Render(RelooperBuilder& Builder, bool InLoop) {
           RemainingConditions = Now;
         }
       }
-      if (isDefault) break;
+      if (IsDefault) break;
     }
   } else {
     // Emit a switch
@@ -240,16 +291,15 @@ wasm::Expression* Block::Render(RelooperBuilder& Builder, bool InLoop) {
       // generate the content for this block
       bool SetCurrLabel = SetLabel && Target->IsCheckedMultipleEntry;
       bool HasFusedContent = Fused && contains(Fused->InnerMap, Target->Id);
+      if (HasFusedContent) {
+        assert(Details->Type == Branch::Break);
+        Details->Type = Branch::Direct;
+      }
       wasm::Expression* CurrContent = nullptr;
       if (SetCurrLabel || Details->Type != Branch::Direct || HasFusedContent || Details->Code) {
         CurrContent = Details->Render(Builder, Target, SetCurrLabel);
         if (HasFusedContent) {
           CurrContent = Builder.blockify(CurrContent, Fused->InnerMap.find(Target->Id)->second->Render(Builder, InLoop));
-        } else if (Details->Type == Branch::Nested) {
-          // Nest the parent content here, and remove it from showing up afterwards as Next
-          assert(Parent->Next);
-          CurrContent = Builder.blockify(CurrContent, Parent->Next->Render(Builder, InLoop));
-          Parent->Next = nullptr;
         }
       }
       // generate a block to branch to, if we have content
@@ -285,15 +335,8 @@ wasm::Expression* Block::Render(RelooperBuilder& Builder, bool InLoop) {
   }
 
   if (Root) {
-    if (Fused) {
-      // We are fusing a multiple into this simple
-      auto* Block = Builder.makeBlock(Root);
-      Block->name = Builder.getBreakName(Fused->Id);
-      Root = Block;
-    }
     Ret->list.push_back(Root);
   }
-
   Ret->finalize();
 
   return Ret;
@@ -303,6 +346,7 @@ wasm::Expression* Block::Render(RelooperBuilder& Builder, bool InLoop) {
 
 wasm::Expression* SimpleShape::Render(RelooperBuilder& Builder, bool InLoop) {
   auto* Ret = Inner->Render(Builder, InLoop);
+  Ret = HandleFollowupMultiples(Ret, this, Builder, InLoop);
   if (Next) {
     Ret = Builder.makeSequence(Ret, Next->Render(Builder, InLoop));
   }
@@ -328,8 +372,8 @@ wasm::Expression* MultipleShape::Render(RelooperBuilder& Builder, bool InLoop) {
       CurrIf = Now;
     }
   }
-  auto* Ret = Builder.makeBlock(FirstIf);
-  Ret->name = Builder.getBreakName(Id);
+  wasm::Expression* Ret = Builder.makeBlock(FirstIf);
+  Ret = HandleFollowupMultiples(Ret, this, Builder, InLoop);
   if (Next) {
     Ret = Builder.makeSequence(Ret, Next->Render(Builder, InLoop));
   }
@@ -339,7 +383,8 @@ wasm::Expression* MultipleShape::Render(RelooperBuilder& Builder, bool InLoop) {
 // LoopShape
 
 wasm::Expression* LoopShape::Render(RelooperBuilder& Builder, bool InLoop) {
-  wasm::Expression* Ret = Builder.makeLoop(Builder.getBreakName(Id), Builder.getContinueName(Id), Inner->Render(Builder, true));
+  wasm::Expression* Ret = Builder.makeLoop(wasm::Name(), Builder.getShapeContinueName(Id), Inner->Render(Builder, true));
+  Ret = HandleFollowupMultiples(Ret, this, Builder, InLoop);
   if (Next) {
     Ret = Builder.makeSequence(Ret, Next->Render(Builder, InLoop));
   }
@@ -455,7 +500,7 @@ void Relooper::Calculate(Block *Entry) {
         BlockSet JustInner;
         JustInner.insert(Inner);
         for (BlockSet::iterator iter = NextEntries.begin(); iter != NextEntries.end(); iter++) {
-          Solipsize(*iter, Branch::Direct, Simple, JustInner);
+          Solipsize(*iter, Branch::Break, Simple, JustInner);
         }
       }
       return Simple;
@@ -570,6 +615,7 @@ void Relooper::Calculate(Block *Entry) {
       // Finish up
       Shape *Inner = Process(InnerBlocks, Entries);
       Loop->Inner = Inner;
+      Loop->Entries = Entries;
       return Loop;
     }
 
@@ -790,7 +836,8 @@ void Relooper::Calculate(Block *Entry) {
         if (IndependentGroups.size() > 0) {
           // We can handle a group in a multiple if its entry cannot be reached by another group.
           // Note that it might be reachable by itself - a loop. But that is fine, we will create
-          // a loop inside the multiple block (which is the performant order to do it).
+          // a loop inside the multiple block, which is both the performant order to do it, and
+          // preserves the property that a loop will always reach an entry.
           for (BlockBlockSetMap::iterator iter = IndependentGroups.begin(); iter != IndependentGroups.end();) {
             Block *Entry = iter->first;
             BlockSet &Group = iter->second;
@@ -853,8 +900,18 @@ void Relooper::Calculate(Block *Entry) {
 
           if (IndependentGroups.size() > 0) {
             // Some groups removable ==> Multiple
-            //                                                                   checked multiple if prev is not simple (in which case we would be fused)
-            Make(MakeMultiple(Blocks, *Entries, IndependentGroups, *NextEntries, !(Shape::IsSimple(Prev))));
+            // This is a checked multiple if it has an entry that is an entry to this Process call, that is,
+            // if we can reach it from outside this set of blocks, then we must check the label variable
+            // to do so. Otherwise, if it is just internal blocks, those can always be jumped to forward,
+            // without using the label variable
+            bool Checked = false;
+            for (auto* Entry : *Entries) {
+              if (InitialEntries.count(Entry)) {
+                Checked = true;
+                break;
+              }
+            }
+            Make(MakeMultiple(Blocks, *Entries, IndependentGroups, *NextEntries, Checked));
           }
         }
         // No independent groups, must be loopable ==> Loop
diff --git a/src/cfg/Relooper.h b/src/cfg/Relooper.h
index 8ac877d08..50f40fd88 100644
--- a/src/cfg/Relooper.h
+++ b/src/cfg/Relooper.h
@@ -53,17 +53,21 @@ public:
   wasm::Binary* makeCheckLabel(wasm::Index value) {
     return makeBinary(wasm::EqInt32, makeGetLabel(), makeConst(wasm::Literal(int32_t(value))));
   }
-  wasm::Break* makeShapeBreak(int id) {
-    return wasm::Builder::makeBreak(getBreakName(id));
+
+  // breaks are on blocks, as they can be specific, we make one wasm block per basic block
+  wasm::Break* makeBlockBreak(int id) {
+    return wasm::Builder::makeBreak(getBlockBreakName(id));
   }
+  // continues are on shapes, as there is one per loop, and if we have more than one
+  // going there, it is irreducible control flow anyhow
   wasm::Break* makeShapeContinue(int id) {
-    return wasm::Builder::makeBreak(getContinueName(id));
+    return wasm::Builder::makeBreak(getShapeContinueName(id));
   }
 
-  wasm::Name getBreakName(int id) {
-    return wasm::Name(std::string("shape$") + std::to_string(id) + "$break");
+  wasm::Name getBlockBreakName(int id) {
+    return wasm::Name(std::string("block$") + std::to_string(id) + "$break");
   }
-  wasm::Name getContinueName(int id) {
+  wasm::Name getShapeContinueName(int id) {
     return wasm::Name(std::string("shape$") + std::to_string(id) + "$continue");
   }
 };
@@ -76,9 +80,7 @@ struct Branch {
   enum FlowType {
     Direct = 0,   // We will directly reach the right location through other means, no need for continue or break
     Break = 1,
-    Continue = 2,
-    Nested = 3    // This code is directly reached, but we must be careful to ensure it is nested in an if - it is not reached
-                  // unconditionally, other code paths exist alongside it that we need to make sure do not intertwine
+    Continue = 2
   };
   Shape *Ancestor; // If not NULL, this shape is the relevant one for purposes of getting to the target block. We break or continue on it
   Branch::FlowType Type; // If Ancestor is not NULL, this says whether to break or continue
@@ -144,12 +146,14 @@ struct InsertOrderedSet
 
   InsertOrderedSet() {}
   InsertOrderedSet(const InsertOrderedSet& other) {
+    *this = other;
+  }
+  InsertOrderedSet& operator=(const InsertOrderedSet& other) {
+    clear();
     for (auto i : other.List) {
       insert(i); // inserting manually creates proper iterators
     }
-  }
-  InsertOrderedSet& operator=(const InsertOrderedSet& other) {
-    abort(); // TODO, watch out for iterators
+    return *this;
   }
 };
 
@@ -241,15 +245,20 @@ struct Block {
 
 // Represents a structured control flow shape, one of
 //
-//  Simple: No control flow at all, just instructions. If several
-//          blocks, then 
+//  Simple: No control flow at all, just instructions in a single
+//          basic block.
 //
-//  Multiple: A shape with more than one entry. If the next block to
-//            be entered is among them, we run it and continue to
-//            the next shape, otherwise we continue immediately to the
-//            next shape.
+//  Multiple: A shape with at least one entry. We may visit one of
+//            the entries, or none, before continuing to the next
+//            shape after this.
 //
-//  Loop: An infinite loop.
+//  Loop: An infinite loop. We assume the property that a loop
+//        will always visit one of its entries, and so for example
+//        we cannot have a loop containing a multiple and nothing
+//        else (since we might not visit any of the multiple's
+//        blocks). Multiple entries are possible for the block,
+//        however, which is necessary for irreducible control
+//        flow, of course.
 //
 
 struct SimpleShape;
@@ -285,7 +294,6 @@ struct SimpleShape : public Shape {
   wasm::Expression* Render(RelooperBuilder& Builder, bool InLoop) override;
 };
 
-// Blocks with the same id were split and are identical, so we just care about ids in Multiple entries
 typedef std::map<int, Shape*> IdShapeMap;
 
 struct MultipleShape : public Shape {
@@ -299,6 +307,8 @@ struct MultipleShape : public Shape {
 struct LoopShape : public Shape {
   Shape *Inner;
 
+  BlockSet Entries; // we must visit at least one of these
+
   LoopShape() : Shape(Loop), Inner(NULL) {}
   wasm::Expression* Render(RelooperBuilder& Builder, bool InLoop) override;
 };
diff --git a/test/example/c-api-kitchen-sink.txt b/test/example/c-api-kitchen-sink.txt
index e541b1704..0d27fa464 100644
--- a/test/example/c-api-kitchen-sink.txt
+++ b/test/example/c-api-kitchen-sink.txt
@@ -381,10 +381,13 @@ raw:
   )
   (func $two-blocks (type $v)
     (local $0 i32)
-    (block
+    (block $block$2$break
       (call_import $check
         (i32.const 0)
       )
+      (block
+        (br $block$2$break)
+      )
     )
     (block
       (call_import $check
@@ -394,12 +397,13 @@ raw:
   )
   (func $two-blocks-plus-code (type $v)
     (local $0 i32)
-    (block
+    (block $block$2$break
       (call_import $check
         (i32.const 0)
       )
       (block
         (i32.const 77)
+        (br $block$2$break)
       )
     )
     (block
@@ -410,11 +414,14 @@ raw:
   )
   (func $loop (type $v)
     (local $0 i32)
-    (loop $shape$0$break $shape$0$continue
-      (block
+    (loop $shape$0$continue
+      (block $block$2$break
         (call_import $check
           (i32.const 0)
         )
+        (block
+          (br $block$2$break)
+        )
       )
       (block
         (call_import $check
@@ -428,13 +435,14 @@ raw:
   )
   (func $loop-plus-code (type $v)
     (local $0 i32)
-    (loop $shape$0$break $shape$0$continue
-      (block
+    (loop $shape$0$continue
+      (block $block$2$break
         (call_import $check
           (i32.const 0)
         )
         (block
           (i32.const 33)
+          (br $block$2$break)
         )
       )
       (block
@@ -453,18 +461,16 @@ raw:
     (call_import $check
       (i32.const 0)
     )
-    (block $shape$1$break
-      (if
-        (i32.const 55)
-        (block
-          (call_import $check
-            (i32.const 1)
-          )
+    (if
+      (i32.const 55)
+      (block
+        (call_import $check
+          (i32.const 1)
         )
-        (block
-          (call_import $check
-            (i32.const 2)
-          )
+      )
+      (block
+        (call_import $check
+          (i32.const 2)
         )
       )
     )
@@ -474,23 +480,21 @@ raw:
     (call_import $check
       (i32.const 0)
     )
-    (block $shape$1$break
-      (if
-        (i32.const 55)
+    (if
+      (i32.const 55)
+      (block
+        (i32.const 10)
         (block
-          (i32.const 10)
-          (block
-            (call_import $check
-              (i32.const 1)
-            )
+          (call_import $check
+            (i32.const 1)
           )
         )
+      )
+      (block
+        (i32.const 20)
         (block
-          (i32.const 20)
-          (block
-            (call_import $check
-              (i32.const 2)
-            )
+          (call_import $check
+            (i32.const 2)
           )
         )
       )
@@ -498,22 +502,21 @@ raw:
   )
   (func $if (type $v)
     (local $0 i32)
-    (block
+    (block $block$3$break
       (call_import $check
         (i32.const 0)
       )
-      (block $shape$1$break
-        (if
-          (i32.const 55)
+      (if
+        (i32.const 55)
+        (block
+          (call_import $check
+            (i32.const 1)
+          )
           (block
-            (call_import $check
-              (i32.const 1)
-            )
-            (block
-              (br $shape$1$break)
-            )
+            (br $block$3$break)
           )
         )
+        (br $block$3$break)
       )
     )
     (block
@@ -524,26 +527,27 @@ raw:
   )
   (func $if-plus-code (type $v)
     (local $0 i32)
-    (block
+    (block $block$3$break
       (call_import $check
         (i32.const 0)
       )
-      (block $shape$1$break
-        (if
-          (i32.const 55)
+      (if
+        (i32.const 55)
+        (block
+          (i32.const -1)
           (block
-            (i32.const -1)
+            (call_import $check
+              (i32.const 1)
+            )
             (block
-              (call_import $check
-                (i32.const 1)
-              )
-              (block
-                (i32.const -3)
-                (br $shape$1$break)
-              )
+              (i32.const -3)
+              (br $block$3$break)
             )
           )
+        )
+        (block
           (i32.const -2)
+          (br $block$3$break)
         )
       )
     )
@@ -555,28 +559,26 @@ raw:
   )
   (func $if-else (type $v)
     (local $0 i32)
-    (block
+    (block $block$4$break
       (call_import $check
         (i32.const 0)
       )
-      (block $shape$1$break
-        (if
-          (i32.const 55)
+      (if
+        (i32.const 55)
+        (block
+          (call_import $check
+            (i32.const 1)
+          )
           (block
-            (call_import $check
-              (i32.const 1)
-            )
-            (block
-              (br $shape$1$break)
-            )
+            (br $block$4$break)
+          )
+        )
+        (block
+          (call_import $check
+            (i32.const 2)
           )
           (block
-            (call_import $check
-              (i32.const 2)
-            )
-            (block
-              (br $shape$1$break)
-            )
+            (br $block$4$break)
           )
         )
       )
@@ -589,20 +591,25 @@ raw:
   )
   (func $loop-tail (type $v)
     (local $0 i32)
-    (loop $shape$0$break $shape$0$continue
-      (block
-        (call_import $check
-          (i32.const 0)
-        )
-      )
-      (block
-        (call_import $check
-          (i32.const 1)
+    (block $block$3$break
+      (loop $shape$0$continue
+        (block $block$2$break
+          (call_import $check
+            (i32.const 0)
+          )
+          (block
+            (br $block$2$break)
+          )
         )
-        (if
-          (i32.const 10)
-          (br $shape$0$continue)
-          (br $shape$0$break)
+        (block
+          (call_import $check
+            (i32.const 1)
+          )
+          (if
+            (i32.const 10)
+            (br $shape$0$continue)
+            (br $block$3$break)
+          )
         )
       )
     )
@@ -614,93 +621,81 @@ raw:
   )
   (func $nontrivial-loop-plus-phi-to-head (type $v)
     (local $0 i32)
-    (block
+    (block $block$2$break
       (call_import $check
         (i32.const 0)
       )
       (block
         (i32.const 10)
+        (br $block$2$break)
       )
     )
     (block
-      (loop $shape$1$break $shape$1$continue
-        (block
-          (call_import $check
-            (i32.const 1)
-          )
-          (if
-            (i32.eqz
-              (i32.const -2)
-            )
-            (block
-              (i32.const 20)
-              (br $shape$1$break)
-            )
-          )
-        )
-        (block
-          (call_import $check
-            (i32.const 2)
-          )
-          (if
-            (i32.const -6)
-            (block
-              (set_local $0
-                (i32.const 4)
+      (block $block$7$break
+        (block $block$4$break
+          (loop $shape$1$continue
+            (block $block$3$break
+              (call_import $check
+                (i32.const 1)
+              )
+              (if
+                (i32.const -2)
+                (br $block$3$break)
+                (block
+                  (i32.const 20)
+                  (br $block$7$break)
+                )
               )
-              (br $shape$1$break)
             )
             (block
-              (i32.const 30)
-              (br $shape$1$continue)
+              (call_import $check
+                (i32.const 2)
+              )
+              (if
+                (i32.const -6)
+                (br $block$4$break)
+                (block
+                  (i32.const 30)
+                  (br $shape$1$continue)
+                )
+              )
             )
           )
         )
-      )
-      (block
-        (block $shape$4$break
-          (if
-            (i32.eq
-              (get_local $0)
-              (i32.const 4)
+        (block
+          (block $block$6$break
+            (call_import $check
+              (i32.const 3)
             )
-            (block
+            (if
+              (i32.const -10)
               (block
                 (call_import $check
-                  (i32.const 3)
-                )
-                (block $shape$6$break
-                  (if
-                    (i32.const -10)
-                    (block
-                      (call_import $check
-                        (i32.const 4)
-                      )
-                      (block
-                        (br $shape$6$break)
-                      )
-                    )
-                  )
-                )
-              )
-              (block
-                (call_import $check
-                  (i32.const 5)
+                  (i32.const 4)
                 )
                 (block
-                  (i32.const 40)
-                  (br $shape$4$break)
+                  (br $block$6$break)
                 )
               )
+              (br $block$6$break)
             )
           )
-        )
-        (block
-          (call_import $check
-            (i32.const 6)
+          (block
+            (call_import $check
+              (i32.const 5)
+            )
+            (block
+              (i32.const 40)
+              (br $block$7$break)
+            )
           )
         )
       )
+      (block
+        (call_import $check
+          (i32.const 6)
+        )
+      )
     )
   )
   (func $switch (type $v)
@@ -708,43 +703,41 @@ raw:
     (call_import $check
       (i32.const 0)
     )
-    (block $shape$1$break
-      (block $switch$1$leave
-        (block $switch$1$default
-          (block $switch$1$case$3
-            (block $switch$1$case$2
-              (br_table $switch$1$default $switch$1$default $switch$1$case$2 $switch$1$default $switch$1$case$3 $switch$1$case$2 $switch$1$default
-                (i32.const -99)
-              )
-            )
-            (block
-              (block
-                (call_import $check
-                  (i32.const 1)
-                )
-              )
+    (block $switch$1$leave
+      (block $switch$1$default
+        (block $switch$1$case$3
+          (block $switch$1$case$2
+            (br_table $switch$1$default $switch$1$default $switch$1$case$2 $switch$1$default $switch$1$case$3 $switch$1$case$2 $switch$1$default
+              (i32.const -99)
             )
-            (br $switch$1$leave)
           )
           (block
-            (i32.const 55)
             (block
               (call_import $check
-                (i32.const 2)
+                (i32.const 1)
               )
             )
           )
           (br $switch$1$leave)
         )
         (block
+          (i32.const 55)
           (block
             (call_import $check
-              (i32.const 3)
+              (i32.const 2)
             )
           )
         )
         (br $switch$1$leave)
       )
+      (block
+        (block
+          (call_import $check
+            (i32.const 3)
+          )
+        )
+      )
+      (br $switch$1$leave)
     )
   )
   (func $duffs-device (type $v)
@@ -756,58 +749,66 @@ raw:
     (local $5 f64)
     (local $6 i32)
     (block
-      (call_import $check
-        (i32.const 0)
+      (block $block$3$break
+        (block $block$2$break
+          (call_import $check
+            (i32.const 0)
+          )
+          (if
+            (i32.const 10)
+            (block
+              (set_local $3
+                (i32.const 2)
+              )
+              (br $block$2$break)
+            )
+            (block
+              (set_local $3
+                (i32.const 3)
+              )
+              (br $block$3$break)
+            )
+          )
+        )
       )
+    )
+    (loop $shape$1$continue
       (if
-        (i32.const 10)
-        (set_local $3
+        (i32.eq
+          (get_local $3)
           (i32.const 2)
         )
-        (set_local $3
-          (i32.const 3)
+        (block
+          (set_local $3
+            (i32.const 0)
+          )
+          (call_import $check
+            (i32.const 1)
+          )
+          (block
+            (set_local $3
+              (i32.const 3)
+            )
+            (br $shape$1$continue)
+          )
         )
-      )
-    )
-    (loop $shape$1$break $shape$1$continue
-      (block $shape$2$break
         (if
           (i32.eq
             (get_local $3)
-            (i32.const 2)
+            (i32.const 3)
           )
           (block
             (set_local $3
               (i32.const 0)
             )
             (call_import $check
-              (i32.const 1)
-            )
-            (block
-              (set_local $3
-                (i32.const 3)
-              )
-              (br $shape$1$continue)
-            )
-          )
-          (if
-            (i32.eq
-              (get_local $3)
-              (i32.const 3)
+              (i32.const 2)
             )
             (block
               (set_local $3
-                (i32.const 0)
-              )
-              (call_import $check
                 (i32.const 2)
               )
-              (block
-                (set_local $3
-                  (i32.const 2)
-                )
-                (br $shape$1$continue)
-              )
+              (br $shape$1$continue)
             )
           )
         )
@@ -847,7 +848,7 @@ optimized:
     )
   )
   (func $loop (type $v)
-    (loop $shape$0$break $shape$0$continue
+    (loop $shape$0$continue
       (call_import $check
         (i32.const 0)
       )
@@ -885,21 +886,6 @@ optimized:
       (i32.const 2)
     )
   )
-  (func $if-plus-code (type $v)
-    (call_import $check
-      (i32.const 0)
-    )
-    (if
-      (i32.const 55)
-      (call_import $check
-        (i32.const 1)
-      )
-      (i32.const -2)
-    )
-    (call_import $check
-      (i32.const 2)
-    )
-  )
   (func $if-else (type $v)
     (call_import $check
       (i32.const 0)
@@ -918,17 +904,19 @@ optimized:
     )
   )
   (func $loop-tail (type $v)
-    (loop $shape$0$break $shape$0$continue
-      (call_import $check
-        (i32.const 0)
-      )
-      (call_import $check
-        (i32.const 1)
-      )
-      (if
-        (i32.const 10)
-        (br $shape$0$continue)
-        (br $shape$0$break)
+    (block $block$3$break
+      (loop $shape$0$continue
+        (call_import $check
+          (i32.const 0)
+        )
+        (call_import $check
+          (i32.const 1)
+        )
+        (if
+          (i32.const 10)
+          (br $shape$0$continue)
+          (br $block$3$break)
+        )
       )
     )
     (call_import $check
@@ -936,50 +924,40 @@ optimized:
     )
   )
   (func $nontrivial-loop-plus-phi-to-head (type $v)
-    (local $0 i32)
     (call_import $check
       (i32.const 0)
     )
-    (loop $shape$1$break $shape$1$continue
-      (call_import $check
-        (i32.const 1)
-      )
-      (br_if $shape$1$break
-        (i32.const 0)
-      )
-      (call_import $check
-        (i32.const 2)
-      )
-      (if
-        (i32.const -6)
-        (block
-          (set_local $0
-            (i32.const 4)
+    (block $block$7$break
+      (block $block$4$break
+        (loop $shape$1$continue
+          (call_import $check
+            (i32.const 1)
+          )
+          (br_if $block$7$break
+            (i32.const 0)
           )
-          (br $shape$1$break)
-        )
-        (br $shape$1$continue)
-      )
-    )
-    (if
-      (i32.eq
-        (get_local $0)
-        (i32.const 4)
-      )
-      (block
-        (call_import $check
-          (i32.const 3)
-        )
-        (if
-          (i32.const -10)
           (call_import $check
-            (i32.const 4)
+            (i32.const 2)
+          )
+          (if
+            (i32.const -6)
+            (br $block$4$break)
+            (br $shape$1$continue)
           )
         )
+      )
+      (call_import $check
+        (i32.const 3)
+      )
+      (if
+        (i32.const -10)
         (call_import $check
-          (i32.const 5)
+          (i32.const 4)
         )
       )
+      (call_import $check
+        (i32.const 5)
+      )
     )
     (call_import $check
       (i32.const 6)
@@ -1020,7 +998,7 @@ optimized:
     (set_local $0
       (i32.const 2)
     )
-    (loop $shape$1$break $shape$1$continue
+    (loop $shape$1$continue
       (if
         (i32.eq
           (get_local $0)
@@ -2246,10 +2224,13 @@ raw:
   )
   (func $two-blocks (type $v)
     (local $0 i32)
-    (block
+    (block $block$2$break
       (call_import $check
         (i32.const 0)
       )
+      (block
+        (br $block$2$break)
+      )
     )
     (block
       (call_import $check
@@ -2259,12 +2240,13 @@ raw:
   )
   (func $two-blocks-plus-code (type $v)
     (local $0 i32)
-    (block
+    (block $block$2$break
       (call_import $check
         (i32.const 0)
       )
       (block
         (i32.const 77)
+        (br $block$2$break)
       )
     )
     (block
@@ -2275,11 +2257,14 @@ raw:
   )
   (func $loop (type $v)
     (local $0 i32)
-    (loop $shape$0$break $shape$0$continue
-      (block
+    (loop $shape$0$continue
+      (block $block$2$break
         (call_import $check
           (i32.const 0)
         )
+        (block
+          (br $block$2$break)
+        )
       )
       (block
         (call_import $check
@@ -2293,13 +2278,14 @@ raw:
   )
   (func $loop-plus-code (type $v)
     (local $0 i32)
-    (loop $shape$0$break $shape$0$continue
-      (block
+    (loop $shape$0$continue
+      (block $block$2$break
         (call_import $check
           (i32.const 0)
         )
         (block
           (i32.const 33)
+          (br $block$2$break)
         )
       )
       (block
@@ -2318,18 +2304,16 @@ raw:
     (call_import $check
       (i32.const 0)
     )
-    (block $shape$1$break
-      (if
-        (i32.const 55)
-        (block
-          (call_import $check
-            (i32.const 1)
-          )
+    (if
+      (i32.const 55)
+      (block
+        (call_import $check
+          (i32.const 1)
         )
-        (block
-          (call_import $check
-            (i32.const 2)
-          )
+      )
+      (block
+        (call_import $check
+          (i32.const 2)
         )
       )
     )
@@ -2339,23 +2323,21 @@ raw:
     (call_import $check
       (i32.const 0)
     )
-    (block $shape$1$break
-      (if
-        (i32.const 55)
+    (if
+      (i32.const 55)
+      (block
+        (i32.const 10)
         (block
-          (i32.const 10)
-          (block
-            (call_import $check
-              (i32.const 1)
-            )
+          (call_import $check
+            (i32.const 1)
           )
         )
+      )
+      (block
+        (i32.const 20)
         (block
-          (i32.const 20)
-          (block
-            (call_import $check
-              (i32.const 2)
-            )
+          (call_import $check
+            (i32.const 2)
           )
         )
       )
@@ -2363,22 +2345,21 @@ raw:
   )
   (func $if (type $v)
     (local $0 i32)
-    (block
+    (block $block$3$break
       (call_import $check
         (i32.const 0)
       )
-      (block $shape$1$break
-        (if
-          (i32.const 55)
+      (if
+        (i32.const 55)
+        (block
+          (call_import $check
+            (i32.const 1)
+          )
           (block
-            (call_import $check
-              (i32.const 1)
-            )
-            (block
-              (br $shape$1$break)
-            )
+            (br $block$3$break)
           )
         )
+        (br $block$3$break)
       )
     )
     (block
@@ -2389,26 +2370,27 @@ raw:
   )
   (func $if-plus-code (type $v)
     (local $0 i32)
-    (block
+    (block $block$3$break
       (call_import $check
         (i32.const 0)
       )
-      (block $shape$1$break
-        (if
-          (i32.const 55)
+      (if
+        (i32.const 55)
+        (block
+          (i32.const -1)
           (block
-            (i32.const -1)
+            (call_import $check
+              (i32.const 1)
+            )
             (block
-              (call_import $check
-                (i32.const 1)
-              )
-              (block
-                (i32.const -3)
-                (br $shape$1$break)
-              )
+              (i32.const -3)
+              (br $block$3$break)
             )
           )
+        )
+        (block
           (i32.const -2)
+          (br $block$3$break)
         )
       )
     )
@@ -2420,28 +2402,26 @@ raw:
   )
   (func $if-else (type $v)
     (local $0 i32)
-    (block
+    (block $block$4$break
       (call_import $check
         (i32.const 0)
       )
-      (block $shape$1$break
-        (if
-          (i32.const 55)
+      (if
+        (i32.const 55)
+        (block
+          (call_import $check
+            (i32.const 1)
+          )
           (block
-            (call_import $check
-              (i32.const 1)
-            )
-            (block
-              (br $shape$1$break)
-            )
+            (br $block$4$break)
+          )
+        )
+        (block
+          (call_import $check
+            (i32.const 2)
           )
           (block
-            (call_import $check
-              (i32.const 2)
-            )
-            (block
-              (br $shape$1$break)
-            )
+            (br $block$4$break)
           )
         )
       )
@@ -2454,20 +2434,25 @@ raw:
   )
   (func $loop-tail (type $v)
     (local $0 i32)
-    (loop $shape$0$break $shape$0$continue
-      (block
-        (call_import $check
-          (i32.const 0)
-        )
-      )
-      (block
-        (call_import $check
-          (i32.const 1)
+    (block $block$3$break
+      (loop $shape$0$continue
+        (block $block$2$break
+          (call_import $check
+            (i32.const 0)
+          )
+          (block
+            (br $block$2$break)
+          )
         )
-        (if
-          (i32.const 10)
-          (br $shape$0$continue)
-          (br $shape$0$break)
+        (block
+          (call_import $check
+            (i32.const 1)
+          )
+          (if
+            (i32.const 10)
+            (br $shape$0$continue)
+            (br $block$3$break)
+          )
         )
       )
     )
@@ -2479,93 +2464,81 @@ raw:
   )
   (func $nontrivial-loop-plus-phi-to-head (type $v)
     (local $0 i32)
-    (block
+    (block $block$2$break
       (call_import $check
         (i32.const 0)
       )
       (block
         (i32.const 10)
+        (br $block$2$break)
       )
     )
     (block
-      (loop $shape$1$break $shape$1$continue
-        (block
-          (call_import $check
-            (i32.const 1)
-          )
-          (if
-            (i32.eqz
-              (i32.const -2)
-            )
-            (block
-              (i32.const 20)
-              (br $shape$1$break)
-            )
-          )
-        )
-        (block
-          (call_import $check
-            (i32.const 2)
-          )
-          (if
-            (i32.const -6)
-            (block
-              (set_local $0
-                (i32.const 4)
+      (block $block$7$break
+        (block $block$4$break
+          (loop $shape$1$continue
+            (block $block$3$break
+              (call_import $check
+                (i32.const 1)
+              )
+              (if
+                (i32.const -2)
+                (br $block$3$break)
+                (block
+                  (i32.const 20)
+                  (br $block$7$break)
+                )
               )
-              (br $shape$1$break)
             )
             (block
-              (i32.const 30)
-              (br $shape$1$continue)
+              (call_import $check
+                (i32.const 2)
+              )
+              (if
+                (i32.const -6)
+                (br $block$4$break)
+                (block
+                  (i32.const 30)
+                  (br $shape$1$continue)
+                )
+              )
             )
           )
         )
-      )
-      (block
-        (block $shape$4$break
-          (if
-            (i32.eq
-              (get_local $0)
-              (i32.const 4)
+        (block
+          (block $block$6$break
+            (call_import $check
+              (i32.const 3)
             )
-            (block
+            (if
+              (i32.const -10)
               (block
                 (call_import $check
-                  (i32.const 3)
-                )
-                (block $shape$6$break
-                  (if
-                    (i32.const -10)
-                    (block
-                      (call_import $check
-                        (i32.const 4)
-                      )
-                      (block
-                        (br $shape$6$break)
-                      )
-                    )
-                  )
-                )
-              )
-              (block
-                (call_import $check
-                  (i32.const 5)
+                  (i32.const 4)
                 )
                 (block
-                  (i32.const 40)
-                  (br $shape$4$break)
+                  (br $block$6$break)
                 )
               )
+              (br $block$6$break)
             )
           )
-        )
-        (block
-          (call_import $check
-            (i32.const 6)
+          (block
+            (call_import $check
+              (i32.const 5)
+            )
+            (block
+              (i32.const 40)
+              (br $block$7$break)
+            )
           )
         )
       )
+      (block
+        (call_import $check
+          (i32.const 6)
+        )
+      )
     )
   )
   (func $switch (type $v)
@@ -2573,43 +2546,41 @@ raw:
     (call_import $check
       (i32.const 0)
     )
-    (block $shape$1$break
-      (block $switch$1$leave
-        (block $switch$1$default
-          (block $switch$1$case$3
-            (block $switch$1$case$2
-              (br_table $switch$1$default $switch$1$default $switch$1$case$2 $switch$1$default $switch$1$case$3 $switch$1$case$2 $switch$1$default
-                (i32.const -99)
-              )
-            )
-            (block
-              (block
-                (call_import $check
-                  (i32.const 1)
-                )
-              )
+    (block $switch$1$leave
+      (block $switch$1$default
+        (block $switch$1$case$3
+          (block $switch$1$case$2
+            (br_table $switch$1$default $switch$1$default $switch$1$case$2 $switch$1$default $switch$1$case$3 $switch$1$case$2 $switch$1$default
+              (i32.const -99)
             )
-            (br $switch$1$leave)
           )
           (block
-            (i32.const 55)
             (block
               (call_import $check
-                (i32.const 2)
+                (i32.const 1)
               )
             )
           )
           (br $switch$1$leave)
         )
         (block
+          (i32.const 55)
           (block
             (call_import $check
-              (i32.const 3)
+              (i32.const 2)
             )
           )
         )
         (br $switch$1$leave)
       )
+      (block
+        (block
+          (call_import $check
+            (i32.const 3)
+          )
+        )
+      )
+      (br $switch$1$leave)
     )
   )
   (func $duffs-device (type $v)
@@ -2621,58 +2592,66 @@ raw:
     (local $5 f64)
     (local $6 i32)
     (block
-      (call_import $check
-        (i32.const 0)
+      (block $block$3$break
+        (block $block$2$break
+          (call_import $check
+            (i32.const 0)
+          )
+          (if
+            (i32.const 10)
+            (block
+              (set_local $3
+                (i32.const 2)
+              )
+              (br $block$2$break)
+            )
+            (block
+              (set_local $3
+                (i32.const 3)
+              )
+              (br $block$3$break)
+            )
+          )
+        )
       )
+    )
+    (loop $shape$1$continue
       (if
-        (i32.const 10)
-        (set_local $3
+        (i32.eq
+          (get_local $3)
           (i32.const 2)
         )
-        (set_local $3
-          (i32.const 3)
+        (block
+          (set_local $3
+            (i32.const 0)
+          )
+          (call_import $check
+            (i32.const 1)
+          )
+          (block
+            (set_local $3
+              (i32.const 3)
+            )
+            (br $shape$1$continue)
+          )
         )
-      )
-    )
-    (loop $shape$1$break $shape$1$continue
-      (block $shape$2$break
         (if
           (i32.eq
             (get_local $3)
-            (i32.const 2)
+            (i32.const 3)
           )
           (block
             (set_local $3
               (i32.const 0)
             )
             (call_import $check
-              (i32.const 1)
-            )
-            (block
-              (set_local $3
-                (i32.const 3)
-              )
-              (br $shape$1$continue)
-            )
-          )
-          (if
-            (i32.eq
-              (get_local $3)
-              (i32.const 3)
+              (i32.const 2)
             )
             (block
               (set_local $3
-                (i32.const 0)
-              )
-              (call_import $check
                 (i32.const 2)
               )
-              (block
-                (set_local $3
-                  (i32.const 2)
-                )
-                (br $shape$1$continue)
-              )
+              (br $shape$1$continue)
             )
           )
         )
@@ -2716,7 +2695,7 @@ optimized:
     )
   )
   (func $loop (type $v)
-    (loop $shape$0$break $shape$0$continue
+    (loop $shape$0$continue
       (call_import $check
         (i32.const 0)
       )
@@ -2754,21 +2733,6 @@ optimized:
       (i32.const 2)
     )
   )
-  (func $if-plus-code (type $v)
-    (call_import $check
-      (i32.const 0)
-    )
-    (if
-      (i32.const 55)
-      (call_import $check
-        (i32.const 1)
-      )
-      (i32.const -2)
-    )
-    (call_import $check
-      (i32.const 2)
-    )
-  )
   (func $if-else (type $v)
     (call_import $check
       (i32.const 0)
@@ -2787,17 +2751,19 @@ optimized:
     )
   )
   (func $loop-tail (type $v)
-    (loop $shape$0$break $shape$0$continue
-      (call_import $check
-        (i32.const 0)
-      )
-      (call_import $check
-        (i32.const 1)
-      )
-      (if
-        (i32.const 10)
-        (br $shape$0$continue)
-        (br $shape$0$break)
+    (block $block$3$break
+      (loop $shape$0$continue
+        (call_import $check
+          (i32.const 0)
+        )
+        (call_import $check
+          (i32.const 1)
+        )
+        (if
+          (i32.const 10)
+          (br $shape$0$continue)
+          (br $block$3$break)
+        )
       )
     )
     (call_import $check
@@ -2805,50 +2771,40 @@ optimized:
     )
   )
   (func $nontrivial-loop-plus-phi-to-head (type $v)
-    (local $0 i32)
     (call_import $check
       (i32.const 0)
     )
-    (loop $shape$1$break $shape$1$continue
-      (call_import $check
-        (i32.const 1)
-      )
-      (br_if $shape$1$break
-        (i32.const 0)
-      )
-      (call_import $check
-        (i32.const 2)
-      )
-      (if
-        (i32.const -6)
-        (block
-          (set_local $0
-            (i32.const 4)
+    (block $block$7$break
+      (block $block$4$break
+        (loop $shape$1$continue
+          (call_import $check
+            (i32.const 1)
+          )
+          (br_if $block$7$break
+            (i32.const 0)
           )
-          (br $shape$1$break)
-        )
-        (br $shape$1$continue)
-      )
-    )
-    (if
-      (i32.eq
-        (get_local $0)
-        (i32.const 4)
-      )
-      (block
-        (call_import $check
-          (i32.const 3)
-        )
-        (if
-          (i32.const -10)
           (call_import $check
-            (i32.const 4)
+            (i32.const 2)
+          )
+          (if
+            (i32.const -6)
+            (br $block$4$break)
+            (br $shape$1$continue)
           )
         )
+      )
+      (call_import $check
+        (i32.const 3)
+      )
+      (if
+        (i32.const -10)
         (call_import $check
-          (i32.const 5)
+          (i32.const 4)
         )
       )
+      (call_import $check
+        (i32.const 5)
+      )
     )
     (call_import $check
       (i32.const 6)
@@ -2889,7 +2845,7 @@ optimized:
     (set_local $0
       (i32.const 2)
     )
-    (loop $shape$1$break $shape$1$continue
+    (loop $shape$1$continue
       (if
         (i32.eq
           (get_local $0)
diff --git a/test/example/c-api-kitchen-sink.txt.txt b/test/example/c-api-kitchen-sink.txt.txt
index 8206ac3d4..0ba8ccf94 100644
--- a/test/example/c-api-kitchen-sink.txt.txt
+++ b/test/example/c-api-kitchen-sink.txt.txt
@@ -375,10 +375,13 @@
   )
   (func $two-blocks (type $v)
     (local $0 i32)
-    (block
+    (block $block$2$break
       (call_import $check
         (i32.const 0)
       )
+      (block
+        (br $block$2$break)
+      )
     )
     (block
       (call_import $check
@@ -388,12 +391,13 @@
   )
   (func $two-blocks-plus-code (type $v)
     (local $0 i32)
-    (block
+    (block $block$2$break
       (call_import $check
         (i32.const 0)
       )
       (block
         (i32.const 77)
+        (br $block$2$break)
       )
     )
     (block
@@ -404,11 +408,14 @@
   )
   (func $loop (type $v)
     (local $0 i32)
-    (loop $shape$0$break $shape$0$continue
-      (block
+    (loop $shape$0$continue
+      (block $block$2$break
         (call_import $check
           (i32.const 0)
         )
+        (block
+          (br $block$2$break)
+        )
       )
       (block
         (call_import $check
@@ -422,13 +429,14 @@
   )
   (func $loop-plus-code (type $v)
     (local $0 i32)
-    (loop $shape$0$break $shape$0$continue
-      (block
+    (loop $shape$0$continue
+      (block $block$2$break
         (call_import $check
           (i32.const 0)
         )
         (block
           (i32.const 33)
+          (br $block$2$break)
         )
       )
       (block
@@ -447,18 +455,16 @@
     (call_import $check
       (i32.const 0)
     )
-    (block $shape$1$break
-      (if
-        (i32.const 55)
-        (block
-          (call_import $check
-            (i32.const 1)
-          )
+    (if
+      (i32.const 55)
+      (block
+        (call_import $check
+          (i32.const 1)
         )
-        (block
-          (call_import $check
-            (i32.const 2)
-          )
+      )
+      (block
+        (call_import $check
+          (i32.const 2)
         )
       )
     )
@@ -468,23 +474,21 @@
     (call_import $check
       (i32.const 0)
     )
-    (block $shape$1$break
-      (if
-        (i32.const 55)
+    (if
+      (i32.const 55)
+      (block
+        (i32.const 10)
         (block
-          (i32.const 10)
-          (block
-            (call_import $check
-              (i32.const 1)
-            )
+          (call_import $check
+            (i32.const 1)
           )
         )
+      )
+      (block
+        (i32.const 20)
         (block
-          (i32.const 20)
-          (block
-            (call_import $check
-              (i32.const 2)
-            )
+          (call_import $check
+            (i32.const 2)
           )
         )
       )
@@ -492,22 +496,21 @@
   )
   (func $if (type $v)
     (local $0 i32)
-    (block
+    (block $block$3$break
       (call_import $check
         (i32.const 0)
       )
-      (block $shape$1$break
-        (if
-          (i32.const 55)
+      (if
+        (i32.const 55)
+        (block
+          (call_import $check
+            (i32.const 1)
+          )
           (block
-            (call_import $check
-              (i32.const 1)
-            )
-            (block
-              (br $shape$1$break)
-            )
+            (br $block$3$break)
           )
         )
+        (br $block$3$break)
       )
     )
     (block
@@ -518,26 +521,27 @@
   )
   (func $if-plus-code (type $v)
     (local $0 i32)
-    (block
+    (block $block$3$break
       (call_import $check
         (i32.const 0)
       )
-      (block $shape$1$break
-        (if
-          (i32.const 55)
+      (if
+        (i32.const 55)
+        (block
+          (i32.const -1)
           (block
-            (i32.const -1)
+            (call_import $check
+              (i32.const 1)
+            )
             (block
-              (call_import $check
-                (i32.const 1)
-              )
-              (block
-                (i32.const -3)
-                (br $shape$1$break)
-              )
+              (i32.const -3)
+              (br $block$3$break)
             )
           )
+        )
+        (block
           (i32.const -2)
+          (br $block$3$break)
         )
       )
     )
@@ -549,28 +553,26 @@
   )
   (func $if-else (type $v)
     (local $0 i32)
-    (block
+    (block $block$4$break
       (call_import $check
         (i32.const 0)
       )
-      (block $shape$1$break
-        (if
-          (i32.const 55)
+      (if
+        (i32.const 55)
+        (block
+          (call_import $check
+            (i32.const 1)
+          )
           (block
-            (call_import $check
-              (i32.const 1)
-            )
-            (block
-              (br $shape$1$break)
-            )
+            (br $block$4$break)
+          )
+        )
+        (block
+          (call_import $check
+            (i32.const 2)
           )
           (block
-            (call_import $check
-              (i32.const 2)
-            )
-            (block
-              (br $shape$1$break)
-            )
+            (br $block$4$break)
           )
         )
       )
@@ -583,20 +585,25 @@
   )
   (func $loop-tail (type $v)
     (local $0 i32)
-    (loop $shape$0$break $shape$0$continue
-      (block
-        (call_import $check
-          (i32.const 0)
-        )
-      )
-      (block
-        (call_import $check
-          (i32.const 1)
+    (block $block$3$break
+      (loop $shape$0$continue
+        (block $block$2$break
+          (call_import $check
+            (i32.const 0)
+          )
+          (block
+            (br $block$2$break)
+          )
         )
-        (if
-          (i32.const 10)
-          (br $shape$0$continue)
-          (br $shape$0$break)
+        (block
+          (call_import $check
+            (i32.const 1)
+          )
+          (if
+            (i32.const 10)
+            (br $shape$0$continue)
+            (br $block$3$break)
+          )
         )
       )
     )
@@ -608,93 +615,81 @@
   )
   (func $nontrivial-loop-plus-phi-to-head (type $v)
     (local $0 i32)
-    (block
+    (block $block$2$break
       (call_import $check
         (i32.const 0)
       )
       (block
         (i32.const 10)
+        (br $block$2$break)
       )
     )
     (block
-      (loop $shape$1$break $shape$1$continue
-        (block
-          (call_import $check
-            (i32.const 1)
-          )
-          (if
-            (i32.eqz
-              (i32.const -2)
-            )
-            (block
-              (i32.const 20)
-              (br $shape$1$break)
-            )
-          )
-        )
-        (block
-          (call_import $check
-            (i32.const 2)
-          )
-          (if
-            (i32.const -6)
-            (block
-              (set_local $0
-                (i32.const 4)
+      (block $block$7$break
+        (block $block$4$break
+          (loop $shape$1$continue
+            (block $block$3$break
+              (call_import $check
+                (i32.const 1)
+              )
+              (if
+                (i32.const -2)
+                (br $block$3$break)
+                (block
+                  (i32.const 20)
+                  (br $block$7$break)
+                )
               )
-              (br $shape$1$break)
             )
             (block
-              (i32.const 30)
-              (br $shape$1$continue)
+              (call_import $check
+                (i32.const 2)
+              )
+              (if
+                (i32.const -6)
+                (br $block$4$break)
+                (block
+                  (i32.const 30)
+                  (br $shape$1$continue)
+                )
+              )
             )
           )
         )
-      )
-      (block
-        (block $shape$4$break
-          (if
-            (i32.eq
-              (get_local $0)
-              (i32.const 4)
+        (block
+          (block $block$6$break
+            (call_import $check
+              (i32.const 3)
             )
-            (block
+            (if
+              (i32.const -10)
               (block
                 (call_import $check
-                  (i32.const 3)
-                )
-                (block $shape$6$break
-                  (if
-                    (i32.const -10)
-                    (block
-                      (call_import $check
-                        (i32.const 4)
-                      )
-                      (block
-                        (br $shape$6$break)
-                      )
-                    )
-                  )
-                )
-              )
-              (block
-                (call_import $check
-                  (i32.const 5)
+                  (i32.const 4)
                 )
                 (block
-                  (i32.const 40)
-                  (br $shape$4$break)
+                  (br $block$6$break)
                 )
               )
+              (br $block$6$break)
             )
           )
-        )
-        (block
-          (call_import $check
-            (i32.const 6)
+          (block
+            (call_import $check
+              (i32.const 5)
+            )
+            (block
+              (i32.const 40)
+              (br $block$7$break)
+            )
           )
         )
       )
+      (block
+        (call_import $check
+          (i32.const 6)
+        )
+      )
     )
   )
   (func $switch (type $v)
@@ -702,43 +697,41 @@
     (call_import $check
       (i32.const 0)
     )
-    (block $shape$1$break
-      (block $switch$1$leave
-        (block $switch$1$default
-          (block $switch$1$case$3
-            (block $switch$1$case$2
-              (br_table $switch$1$default $switch$1$default $switch$1$case$2 $switch$1$default $switch$1$case$3 $switch$1$case$2 $switch$1$default
-                (i32.const -99)
-              )
-            )
-            (block
-              (block
-                (call_import $check
-                  (i32.const 1)
-                )
-              )
+    (block $switch$1$leave
+      (block $switch$1$default
+        (block $switch$1$case$3
+          (block $switch$1$case$2
+            (br_table $switch$1$default $switch$1$default $switch$1$case$2 $switch$1$default $switch$1$case$3 $switch$1$case$2 $switch$1$default
+              (i32.const -99)
             )
-            (br $switch$1$leave)
           )
           (block
-            (i32.const 55)
             (block
               (call_import $check
-                (i32.const 2)
+                (i32.const 1)
               )
             )
           )
           (br $switch$1$leave)
         )
         (block
+          (i32.const 55)
           (block
             (call_import $check
-              (i32.const 3)
+              (i32.const 2)
             )
           )
         )
         (br $switch$1$leave)
       )
+      (block
+        (block
+          (call_import $check
+            (i32.const 3)
+          )
+        )
+      )
+      (br $switch$1$leave)
     )
   )
   (func $duffs-device (type $v)
@@ -750,58 +743,66 @@
     (local $5 f64)
     (local $6 i32)
     (block
-      (call_import $check
-        (i32.const 0)
+      (block $block$3$break
+        (block $block$2$break
+          (call_import $check
+            (i32.const 0)
+          )
+          (if
+            (i32.const 10)
+            (block
+              (set_local $3
+                (i32.const 2)
+              )
+              (br $block$2$break)
+            )
+            (block
+              (set_local $3
+                (i32.const 3)
+              )
+              (br $block$3$break)
+            )
+          )
+        )
       )
+    )
+    (loop $shape$1$continue
       (if
-        (i32.const 10)
-        (set_local $3
+        (i32.eq
+          (get_local $3)
           (i32.const 2)
         )
-        (set_local $3
-          (i32.const 3)
+        (block
+          (set_local $3
+            (i32.const 0)
+          )
+          (call_import $check
+            (i32.const 1)
+          )
+          (block
+            (set_local $3
+              (i32.const 3)
+            )
+            (br $shape$1$continue)
+          )
         )
-      )
-    )
-    (loop $shape$1$break $shape$1$continue
-      (block $shape$2$break
         (if
           (i32.eq
             (get_local $3)
-            (i32.const 2)
+            (i32.const 3)
           )
           (block
             (set_local $3
               (i32.const 0)
             )
             (call_import $check
-              (i32.const 1)
-            )
-            (block
-              (set_local $3
-                (i32.const 3)
-              )
-              (br $shape$1$continue)
-            )
-          )
-          (if
-            (i32.eq
-              (get_local $3)
-              (i32.const 3)
+              (i32.const 2)
             )
             (block
               (set_local $3
-                (i32.const 0)
-              )
-              (call_import $check
                 (i32.const 2)
               )
-              (block
-                (set_local $3
-                  (i32.const 2)
-                )
-                (br $shape$1$continue)
-              )
+              (br $shape$1$continue)
             )
           )
         )
@@ -840,7 +841,7 @@
     )
   )
   (func $loop (type $v)
-    (loop $shape$0$break $shape$0$continue
+    (loop $shape$0$continue
       (call_import $check
         (i32.const 0)
       )
@@ -878,21 +879,6 @@
       (i32.const 2)
     )
   )
-  (func $if-plus-code (type $v)
-    (call_import $check
-      (i32.const 0)
-    )
-    (if
-      (i32.const 55)
-      (call_import $check
-        (i32.const 1)
-      )
-      (i32.const -2)
-    )
-    (call_import $check
-      (i32.const 2)
-    )
-  )
   (func $if-else (type $v)
     (call_import $check
       (i32.const 0)
@@ -911,17 +897,19 @@
     )
   )
   (func $loop-tail (type $v)
-    (loop $shape$0$break $shape$0$continue
-      (call_import $check
-        (i32.const 0)
-      )
-      (call_import $check
-        (i32.const 1)
-      )
-      (if
-        (i32.const 10)
-        (br $shape$0$continue)
-        (br $shape$0$break)
+    (block $block$3$break
+      (loop $shape$0$continue
+        (call_import $check
+          (i32.const 0)
+        )
+        (call_import $check
+          (i32.const 1)
+        )
+        (if
+          (i32.const 10)
+          (br $shape$0$continue)
+          (br $block$3$break)
+        )
       )
     )
     (call_import $check
@@ -929,50 +917,40 @@
     )
   )
   (func $nontrivial-loop-plus-phi-to-head (type $v)
-    (local $0 i32)
     (call_import $check
       (i32.const 0)
     )
-    (loop $shape$1$break $shape$1$continue
-      (call_import $check
-        (i32.const 1)
-      )
-      (br_if $shape$1$break
-        (i32.const 0)
-      )
-      (call_import $check
-        (i32.const 2)
-      )
-      (if
-        (i32.const -6)
-        (block
-          (set_local $0
-            (i32.const 4)
+    (block $block$7$break
+      (block $block$4$break
+        (loop $shape$1$continue
+          (call_import $check
+            (i32.const 1)
+          )
+          (br_if $block$7$break
+            (i32.const 0)
           )
-          (br $shape$1$break)
-        )
-        (br $shape$1$continue)
-      )
-    )
-    (if
-      (i32.eq
-        (get_local $0)
-        (i32.const 4)
-      )
-      (block
-        (call_import $check
-          (i32.const 3)
-        )
-        (if
-          (i32.const -10)
           (call_import $check
-            (i32.const 4)
+            (i32.const 2)
+          )
+          (if
+            (i32.const -6)
+            (br $block$4$break)
+            (br $shape$1$continue)
           )
         )
+      )
+      (call_import $check
+        (i32.const 3)
+      )
+      (if
+        (i32.const -10)
         (call_import $check
-          (i32.const 5)
+          (i32.const 4)
         )
       )
+      (call_import $check
+        (i32.const 5)
+      )
     )
     (call_import $check
       (i32.const 6)
@@ -1013,7 +991,7 @@
     (set_local $0
       (i32.const 2)
     )
-    (loop $shape$1$break $shape$1$continue
+    (loop $shape$1$continue
       (if
         (i32.eq
           (get_local $0)
diff --git a/test/example/relooper-fuzz.txt b/test/example/relooper-fuzz.txt
index 6da66a8c9..b4e6c8b57 100644
--- a/test/example/relooper-fuzz.txt
+++ b/test/example/relooper-fuzz.txt
@@ -154,44 +154,49 @@
     )
     (block
       (block
-        (block
-          (call_import $print
-            (i32.const 0)
-          )
-          (set_local $0
-            (call $check)
-          )
-        )
-        (block $shape$1$break
-          (if
-            (i32.eq
-              (i32.rem_u
-                (get_local $0)
-                (i32.const 2)
+        (block $block$6$break
+          (block $block$5$break
+            (block
+              (call_import $print
+                (i32.const 0)
+              )
+              (set_local $0
+                (call $check)
               )
-              (i32.const 0)
-            )
-            (set_local $1
-              (i32.const 6)
             )
-            (block
-              (block
-                (call_import $print
-                  (i32.const 8)
+            (if
+              (i32.eq
+                (i32.rem_u
+                  (get_local $0)
+                  (i32.const 2)
                 )
-                (set_local $0
-                  (call $check)
+                (i32.const 0)
+              )
+              (block
+                (set_local $1
+                  (i32.const 6)
                 )
+                (br $block$6$break)
               )
               (block
-                (br $shape$1$break)
+                (block
+                  (call_import $print
+                    (i32.const 8)
+                  )
+                  (set_local $0
+                    (call $check)
+                  )
+                )
+                (block
+                  (br $block$5$break)
+                )
               )
             )
           )
         )
       )
-      (loop $shape$3$break $shape$3$continue
-        (block $shape$4$break
+      (loop $shape$3$continue
+        (block $block$5$break
           (if
             (i32.eq
               (get_local $1)
@@ -229,7 +234,7 @@
           )
         )
         (block
-          (block
+          (block $block$3$break
             (block
               (call_import $print
                 (i32.const 4)
@@ -261,6 +266,7 @@
                   )
                   (br $shape$3$continue)
                 )
+                (br $block$3$break)
               )
             )
           )
@@ -460,7 +466,7 @@
         (call $check)
       )
     )
-    (loop $shape$3$break $shape$3$continue
+    (loop $shape$3$continue
       (if
         (i32.eq
           (get_local $0)
diff --git a/test/example/relooper-fuzz1.txt b/test/example/relooper-fuzz1.txt
index baef772c8..437dab062 100644
--- a/test/example/relooper-fuzz1.txt
+++ b/test/example/relooper-fuzz1.txt
@@ -165,26 +165,16 @@
       (i32.const 3)
     )
     (block
-      (block
-        (block
-          (call_import $print
-            (i32.const 0)
-          )
-          (set_local $0
-            (call $check)
-          )
-        )
-        (block $shape$1$break
-          (if
-            (i32.eq
-              (i32.rem_u
-                (get_local $0)
-                (i32.const 4)
+      (block $block$10$break
+        (block $block$4$break
+          (block $block$3$break
+            (block
+              (call_import $print
+                (i32.const 0)
+              )
+              (set_local $0
+                (call $check)
               )
-              (i32.const 0)
-            )
-            (set_local $1
-              (i32.const 3)
             )
             (if
               (i32.eq
@@ -192,127 +182,87 @@
                   (get_local $0)
                   (i32.const 4)
                 )
-                (i32.const 2)
-              )
-              (block
-                (block
-                  (call_import $print
-                    (i32.const 7)
-                  )
-                  (set_local $0
-                    (call $check)
-                  )
-                )
-                (if
-                  (i32.eq
-                    (i32.rem_u
-                      (get_local $0)
-                      (i32.const 3)
-                    )
-                    (i32.const 0)
-                  )
-                  (block
-                    (set_local $1
-                      (i32.const 3)
-                    )
-                    (br $shape$1$break)
-                  )
-                  (block
-                    (set_local $1
-                      (i32.const 10)
-                    )
-                    (br $shape$1$break)
-                  )
-                )
-              )
-              (set_local $1
-                (i32.const 4)
-              )
-            )
-          )
-        )
-      )
-      (block
-        (block $shape$3$break
-          (if
-            (i32.eq
-              (get_local $1)
-              (i32.const 3)
-            )
-            (block
-              (block
-                (call_import $print
-                  (i32.const 2)
-                )
-                (set_local $0
-                  (call $check)
-                )
+                (i32.const 0)
               )
+              (br $block$3$break)
               (if
                 (i32.eq
                   (i32.rem_u
                     (get_local $0)
-                    (i32.const 2)
-                  )
-                  (i32.const 0)
-                )
-                (block
-                  (set_local $1
                     (i32.const 4)
                   )
-                  (br $shape$3$break)
+                  (i32.const 2)
                 )
                 (block
-                  (set_local $1
-                    (i32.const 10)
+                  (block
+                    (call_import $print
+                      (i32.const 7)
+                    )
+                    (set_local $0
+                      (call $check)
+                    )
+                  )
+                  (if
+                    (i32.eq
+                      (i32.rem_u
+                        (get_local $0)
+                        (i32.const 3)
+                      )
+                      (i32.const 0)
+                    )
+                    (br $block$3$break)
+                    (br $block$10$break)
                   )
-                  (br $shape$3$break)
                 )
+                (br $block$4$break)
               )
             )
           )
-        )
-        (block $shape$5$break
-          (if
-            (i32.eq
-              (get_local $1)
-              (i32.const 4)
-            )
-            (loop $shape$6$break $shape$6$continue
-              (set_local $1
-                (i32.const 0)
-              )
-              (block
-                (call_import $print
-                  (i32.const 3)
-                )
-                (set_local $0
-                  (call $check)
-                )
+          (block
+            (block
+              (call_import $print
+                (i32.const 2)
               )
-              (block
-                (set_local $1
-                  (i32.const 4)
-                )
-                (br $shape$6$continue)
+              (set_local $0
+                (call $check)
               )
             )
             (if
               (i32.eq
-                (get_local $1)
-                (i32.const 10)
-              )
-              (block
-                (call_import $print
-                  (i32.const 9)
-                )
-                (set_local $0
-                  (call $check)
+                (i32.rem_u
+                  (get_local $0)
+                  (i32.const 2)
                 )
+                (i32.const 0)
               )
+              (br $block$4$break)
+              (br $block$10$break)
             )
           )
         )
+        (loop $shape$6$continue
+          (block
+            (call_import $print
+              (i32.const 3)
+            )
+            (set_local $0
+              (call $check)
+            )
+          )
+          (block
+            (br $shape$6$continue)
+          )
+        )
+      )
+      (block
+        (block
+          (call_import $print
+            (i32.const 9)
+          )
+          (set_local $0
+            (call $check)
+          )
+        )
       )
     )
   )
@@ -482,96 +432,70 @@
       (i32.const 124)
       (i32.const 3)
     )
-    (call_import $print
-      (i32.const 0)
-    )
-    (if
-      (i32.eq
-        (set_local $0
+    (block $block$10$break
+      (block $block$4$break
+        (call_import $print
+          (i32.const 0)
+        )
+        (if
+          (i32.ne
+            (i32.rem_u
+              (set_local $0
+                (call $check)
+              )
+              (i32.const 4)
+            )
+            (i32.const 0)
+          )
           (if
             (i32.eq
               (i32.rem_u
-                (set_local $0
-                  (call $check)
-                )
+                (get_local $0)
                 (i32.const 4)
               )
-              (i32.const 0)
+              (i32.const 2)
             )
-            (i32.const 3)
-            (if
-              (i32.eq
-                (i32.rem_u
-                  (get_local $0)
-                  (i32.const 4)
-                )
-                (i32.const 2)
+            (block
+              (call_import $print
+                (i32.const 7)
               )
-              (block
-                (call_import $print
-                  (i32.const 7)
-                )
-                (if
-                  (i32.eq
-                    (i32.rem_u
-                      (call $check)
-                      (i32.const 3)
-                    )
-                    (i32.const 0)
+              (br_if $block$10$break
+                (i32.ne
+                  (i32.rem_u
+                    (call $check)
+                    (i32.const 3)
                   )
-                  (i32.const 3)
-                  (i32.const 10)
+                  (i32.const 0)
                 )
               )
-              (i32.const 4)
             )
+            (br $block$4$break)
           )
         )
-        (i32.const 3)
-      )
-      (block
         (call_import $print
           (i32.const 2)
         )
-        (set_local $0
-          (if
-            (i32.eq
-              (i32.rem_u
-                (call $check)
-                (i32.const 2)
-              )
-              (i32.const 0)
+        (br_if $block$10$break
+          (i32.ne
+            (i32.rem_u
+              (call $check)
+              (i32.const 2)
             )
-            (i32.const 4)
-            (i32.const 10)
+            (i32.const 0)
           )
         )
       )
-    )
-    (if
-      (i32.eq
-        (get_local $0)
-        (i32.const 4)
-      )
-      (loop $shape$6$break $shape$6$continue
+      (loop $shape$6$continue
         (call_import $print
           (i32.const 3)
         )
         (call $check)
         (br $shape$6$continue)
       )
-      (if
-        (i32.eq
-          (get_local $0)
-          (i32.const 10)
-        )
-        (block
-          (call_import $print
-            (i32.const 9)
-          )
-          (call $check)
-        )
-      )
     )
+    (call_import $print
+      (i32.const 9)
+    )
+    (call $check)
   )
 )