fix br_if with value optimization in remove-unused-brs

8 files changed, 173 insertions, 0 deletions

diff --git a/src/passes/RemoveUnusedBrs.cpp b/src/passes/RemoveUnusedBrs.cpp
index ffdba0768..3f909c32e 100644
--- a/src/passes/RemoveUnusedBrs.cpp
+++ b/src/passes/RemoveUnusedBrs.cpp
@@ -128,6 +128,13 @@ struct RemoveUnusedBrs : public WalkerPass<PostWalker<RemoveUnusedBrs, Visitor<R
       // if without an else. try to reduce   if (condition) br  =>  br_if (condition)
       Break* br = curr->ifTrue->dynCast<Break>();
       if (br && !br->condition) { // TODO: if there is a condition, join them
+        // if the br has a value, then if => br_if means we always execute the value, and also the order is value,condition vs condition,value
+        if (br->value) {
+          EffectAnalyzer value(br->value);
+          if (value.hasSideEffects()) return;
+          EffectAnalyzer condition(curr->condition);
+          if (condition.invalidates(value)) return;
+        }
         br->condition = curr->condition;
         replaceCurrent(br);
         anotherCycle = true;
diff --git a/test/passes/remove-unused-brs.txt b/test/passes/remove-unused-brs.txt
index a8e7f29be..c3ac71057 100644
--- a/test/passes/remove-unused-brs.txt
+++ b/test/passes/remove-unused-brs.txt
@@ -281,4 +281,45 @@
       )
     )
   )
+  (func $side-effects-and-order (result i32)
+    (local $x i32)
+    (block $do-once$0
+      (br_if $do-once$0
+        (i32.const 0)
+        (call $b13)
+      )
+      (i32.const 1)
+    )
+    (block $do-once$0
+      (if
+        (call $b13)
+        (br $do-once$0
+          (call $b14)
+        )
+      )
+      (i32.const 1)
+    )
+    (block $do-once$0
+      (if
+        (i32.const 0)
+        (br $do-once$0
+          (call $b14)
+        )
+      )
+      (i32.const 1)
+    )
+    (block $do-once$0
+      (if
+        (set_local $x
+          (i32.const 1)
+        )
+        (br $do-once$0
+          (set_local $x
+            (i32.const 2)
+          )
+        )
+      )
+      (i32.const 1)
+    )
+  )
 )
diff --git a/test/passes/remove-unused-brs.wast b/test/passes/remove-unused-brs.wast
index 8b9d42bc1..b7dc1cc25 100644
--- a/test/passes/remove-unused-brs.wast
+++ b/test/passes/remove-unused-brs.wast
@@ -297,5 +297,44 @@
       )
     )
   )
+  (func $side-effects-and-order (result i32)
+    (local $x i32)
+    (block $do-once$0
+      (if
+        (call $b13)
+        (br $do-once$0
+          (i32.const 0)
+        )
+      )
+      (i32.const 1)
+    )
+    (block $do-once$0
+      (if
+        (call $b13)
+        (br $do-once$0
+          (call $b14)
+        )
+      )
+      (i32.const 1)
+    )
+    (block $do-once$0
+      (if
+        (i32.const 0)
+        (br $do-once$0
+          (call $b14)
+        )
+      )
+      (i32.const 1)
+    )
+    (block $do-once$0
+      (if
+        (set_local $x (i32.const 1))
+        (br $do-once$0
+          (set_local $x (i32.const 2))
+        )
+      )
+      (i32.const 1)
+    )
+  )
 )
 
diff --git a/test/unit.asm.js b/test/unit.asm.js
index 2f307e085..b0e4e7594 100644
--- a/test/unit.asm.js
+++ b/test/unit.asm.js
@@ -247,6 +247,18 @@ function asm(global, env, buffer) {
     }
   }
 
+  function phi() {
+    var x = 0;
+    do {
+      if (lb(1) | 0) {
+        x = 0;
+        break;
+      }
+      x = 1;
+    } while (0);
+    return x | 0;
+  }
+
   function z() {
   }
   function w() {
diff --git a/test/unit.fromasm b/test/unit.fromasm
index 3fb76981d..54b790edf 100644
--- a/test/unit.fromasm
+++ b/test/unit.fromasm
@@ -453,4 +453,17 @@
       )
     )
   )
+  (func $phi (result i32)
+    (block $do-once$0
+      (if
+        (call $lb
+          (i32.const 1)
+        )
+        (br $do-once$0
+          (i32.const 0)
+        )
+      )
+      (i32.const 1)
+    )
+  )
 )
diff --git a/test/unit.fromasm.imprecise b/test/unit.fromasm.imprecise
index a4716941d..b7b25e9b8 100644
--- a/test/unit.fromasm.imprecise
+++ b/test/unit.fromasm.imprecise
@@ -445,4 +445,17 @@
       )
     )
   )
+  (func $phi (result i32)
+    (block $do-once$0
+      (if
+        (call $lb
+          (i32.const 1)
+        )
+        (br $do-once$0
+          (i32.const 0)
+        )
+      )
+      (i32.const 1)
+    )
+  )
 )
diff --git a/test/unit.fromasm.imprecise.no-opts b/test/unit.fromasm.imprecise.no-opts
index c3da01359..9f49824f3 100644
--- a/test/unit.fromasm.imprecise.no-opts
+++ b/test/unit.fromasm.imprecise.no-opts
@@ -721,6 +721,30 @@
       )
     )
   )
+  (func $phi (result i32)
+    (local $x i32)
+    (block $do-once$0
+      (block
+        (if
+          (call $lb
+            (i32.const 1)
+          )
+          (block
+            (set_local $x
+              (i32.const 0)
+            )
+            (br $do-once$0)
+          )
+        )
+        (set_local $x
+          (i32.const 1)
+        )
+      )
+    )
+    (return
+      (get_local $x)
+    )
+  )
   (func $z
     (nop)
   )
diff --git a/test/unit.fromasm.no-opts b/test/unit.fromasm.no-opts
index 92d2d2add..ccf89c5b6 100644
--- a/test/unit.fromasm.no-opts
+++ b/test/unit.fromasm.no-opts
@@ -725,6 +725,30 @@
       )
     )
   )
+  (func $phi (result i32)
+    (local $x i32)
+    (block $do-once$0
+      (block
+        (if
+          (call $lb
+            (i32.const 1)
+          )
+          (block
+            (set_local $x
+              (i32.const 0)
+            )
+            (br $do-once$0)
+          )
+        )
+        (set_local $x
+          (i32.const 1)
+        )
+      )
+    )
+    (return
+      (get_local $x)
+    )
+  )
   (func $z
     (nop)
   )