2 files changed, 55 insertions, 25 deletions

diff --git a/src/passes/MergeBlocks.cpp b/src/passes/MergeBlocks.cpp
index d32948bee..7c086a920 100644
--- a/src/passes/MergeBlocks.cpp
+++ b/src/passes/MergeBlocks.cpp
@@ -73,14 +73,23 @@ namespace wasm {
 // For example, if there is a switch targeting us, we can't do it - we can't remove the value from other targets
 struct ProblemFinder : public ControlFlowWalker<ProblemFinder> {
   Name origin;
-  bool foundSwitch = false;
+  bool foundProblem = false;
   // count br_ifs, and dropped br_ifs. if they don't match, then a br_if flow value is used, and we can't drop it
   Index brIfs = 0;
   Index droppedBrIfs = 0;
+  PassOptions& passOptions;
+
+  ProblemFinder(PassOptions& passOptions) : passOptions(passOptions) {}
 
   void visitBreak(Break* curr) {
-    if (curr->name == origin && curr->condition) {
-      brIfs++;
+    if (curr->name == origin) {
+      if (curr->condition) {
+        brIfs++;
+      }
+      // if the value has side effects, we can't remove it
+      if (EffectAnalyzer(passOptions, curr->value).hasSideEffects()) {
+        foundProblem = true;
+      }
     }
   }
 
@@ -94,12 +103,12 @@ struct ProblemFinder : public ControlFlowWalker<ProblemFinder> {
 
   void visitSwitch(Switch* curr) {
     if (curr->default_ == origin) {
-      foundSwitch = true;
+      foundProblem = true;
       return;
     }
     for (auto& target : curr->targets) {
       if (target == origin) {
-        foundSwitch = true;
+        foundProblem = true;
         return;
       }
     }
@@ -107,7 +116,7 @@ struct ProblemFinder : public ControlFlowWalker<ProblemFinder> {
 
   bool found() {
     assert(brIfs >= droppedBrIfs);
-    return foundSwitch || brIfs > droppedBrIfs;
+    return foundProblem || brIfs > droppedBrIfs;
   }
 };
 
@@ -115,6 +124,9 @@ struct ProblemFinder : public ControlFlowWalker<ProblemFinder> {
 // While doing so it can create new blocks, so optimize blocks as well.
 struct BreakValueDropper : public ControlFlowWalker<BreakValueDropper> {
   Name origin;
+  PassOptions& passOptions;
+
+  BreakValueDropper(PassOptions& passOptions) : passOptions(passOptions) {}
 
   void visitBlock(Block* curr);
 
@@ -143,7 +155,7 @@ struct BreakValueDropper : public ControlFlowWalker<BreakValueDropper> {
 };
 
 // core block optimizer routine
-static void optimizeBlock(Block* curr, Module* module) {
+static void optimizeBlock(Block* curr, Module* module, PassOptions& passOptions) {
   bool more = true;
   bool changed = false;
   while (more) {
@@ -159,14 +171,14 @@ static void optimizeBlock(Block* curr, Module* module) {
             if (child->name.is()) {
               Expression* expression = child;
               // check if it's ok to remove the value from all breaks to us
-              ProblemFinder finder;
+              ProblemFinder finder(passOptions);
               finder.origin = child->name;
               finder.walk(expression);
               if (finder.found()) {
                 child = nullptr;
               } else {
                 // fix up breaks
-                BreakValueDropper fixer;
+                BreakValueDropper fixer(passOptions);
                 fixer.origin = child->name;
                 fixer.setModule(module);
                 fixer.walk(expression);
@@ -217,7 +229,7 @@ static void optimizeBlock(Block* curr, Module* module) {
 }
 
 void BreakValueDropper::visitBlock(Block* curr) {
-  optimizeBlock(curr, getModule());
+  optimizeBlock(curr, getModule(), passOptions);
 }
 
 struct MergeBlocks : public WalkerPass<PostWalker<MergeBlocks>> {
@@ -226,7 +238,7 @@ struct MergeBlocks : public WalkerPass<PostWalker<MergeBlocks>> {
   Pass* create() override { return new MergeBlocks; }
 
   void visitBlock(Block *curr) {
-    optimizeBlock(curr, getModule());
+    optimizeBlock(curr, getModule(), getPassOptions());
   }
 
   Block* optimize(Expression* curr, Expression*& child, Block* outer = nullptr, Expression** dependency1 = nullptr, Expression** dependency2 = nullptr) {
diff --git a/src/passes/OptimizeInstructions.cpp b/src/passes/OptimizeInstructions.cpp
index de6f96ccc..4fd7cbe8d 100644
--- a/src/passes/OptimizeInstructions.cpp
+++ b/src/passes/OptimizeInstructions.cpp
@@ -29,6 +29,7 @@
 #include <ast/effects.h>
 #include <ast/manipulation.h>
 #include <ast/properties.h>
+#include <ast/literal-utils.h>
 
 namespace wasm {
 
@@ -188,14 +189,14 @@ Index getMaxBits(Expression* curr, LocalInfoProvider* localInfoProvider) {
       case OrInt32: case XorInt32: return std::max(getMaxBits(binary->left, localInfoProvider), getMaxBits(binary->right, localInfoProvider));
       case ShlInt32: {
         if (auto* shifts = binary->right->dynCast<Const>()) {
-          return std::min(Index(32), getMaxBits(binary->left, localInfoProvider) + shifts->value.geti32());
+          return std::min(Index(32), getMaxBits(binary->left, localInfoProvider) + Bits::getEffectiveShifts(shifts));
         }
         return 32;
       }
       case ShrUInt32: {
         if (auto* shift = binary->right->dynCast<Const>()) {
           auto maxBits = getMaxBits(binary->left, localInfoProvider);
-          auto shifts = std::min(Index(shift->value.geti32()), maxBits); // can ignore more shifts than zero us out
+          auto shifts = std::min(Index(Bits::getEffectiveShifts(shift)), maxBits); // can ignore more shifts than zero us out
           return std::max(Index(0), maxBits - shifts);
         }
         return 32;
@@ -204,7 +205,7 @@ Index getMaxBits(Expression* curr, LocalInfoProvider* localInfoProvider) {
         if (auto* shift = binary->right->dynCast<Const>()) {
           auto maxBits = getMaxBits(binary->left, localInfoProvider);
           if (maxBits == 32) return 32;
-          auto shifts = std::min(Index(shift->value.geti32()), maxBits); // can ignore more shifts than zero us out
+          auto shifts = std::min(Index(Bits::getEffectiveShifts(shift)), maxBits); // can ignore more shifts than zero us out
           return std::max(Index(0), maxBits - shifts);
         }
         return 32;
@@ -533,9 +534,16 @@ struct OptimizeInstructions : public WalkerPass<PostWalker<OptimizeInstructions,
               } else if (left->op == OrInt32) {
                 leftRight->value = leftRight->value.or_(right->value);
                 return left;
-              } else if (left->op == ShlInt32 || left->op == ShrUInt32 || left->op == ShrSInt32) {
-                leftRight->value = leftRight->value.add(right->value);
-                return left;
+              } else if (left->op == ShlInt32 || left->op == ShrUInt32 || left->op == ShrSInt32 ||
+                         left->op == ShlInt64 || left->op == ShrUInt64 || left->op == ShrSInt64) {
+                // shifts only use an effective amount from the constant, so adding must
+                // be done carefully
+                auto total = Bits::getEffectiveShifts(leftRight) + Bits::getEffectiveShifts(right);
+                if (total == Bits::getEffectiveShifts(total, right->type)) {
+                  // no overflow, we can do this
+                  leftRight->value = LiteralUtils::makeLiteralFromInt32(total, right->type);
+                  return left;
+                } // TODO: handle overflows
               }
             }
           }
@@ -874,14 +882,17 @@ private:
     auto* left = binary->left;
     auto* right = binary->right;
     if (!Properties::emitsBoolean(left) || !Properties::emitsBoolean(right)) return nullptr;
-    auto leftEffects = EffectAnalyzer(getPassOptions(), left).hasSideEffects();
-    auto rightEffects = EffectAnalyzer(getPassOptions(), right).hasSideEffects();
-    if (leftEffects && rightEffects) return nullptr; // both must execute
-   // canonicalize with side effects, if any, happening on the left
-    if (rightEffects) {
+    auto leftEffects = EffectAnalyzer(getPassOptions(), left);
+    auto rightEffects = EffectAnalyzer(getPassOptions(), right);
+    auto leftHasSideEffects = leftEffects.hasSideEffects();
+    auto rightHasSideEffects = rightEffects.hasSideEffects();
+    if (leftHasSideEffects && rightHasSideEffects) return nullptr; // both must execute
+    // canonicalize with side effects, if any, happening on the left
+    if (rightHasSideEffects) {
       if (CostAnalyzer(left).cost < MIN_COST) return nullptr; // avoidable code is too cheap
+      if (leftEffects.invalidates(rightEffects)) return nullptr; // cannot reorder
       std::swap(left, right);
-    } else if (leftEffects) {
+    } else if (leftHasSideEffects) {
       if (CostAnalyzer(right).cost < MIN_COST) return nullptr; // avoidable code is too cheap
     } else {
       // no side effects, reorder based on cost estimation
@@ -908,8 +919,15 @@ private:
     // it's better to do the opposite for gzip purposes as well as for readability.
     auto* last = ptr->dynCast<Const>();
     if (last) {
-      last->value = Literal(int32_t(last->value.geti32() + offset));
-      offset = 0;
+      // don't do this if it would wrap the pointer
+      uint64_t value64 = last->value.geti32();
+      uint64_t offset64 = offset;
+      if (value64 <= std::numeric_limits<int32_t>::max() &&
+          offset64 <= std::numeric_limits<int32_t>::max() &&
+          value64 + offset64 <= std::numeric_limits<int32_t>::max()) {
+        last->value = Literal(int32_t(value64 + offset64));
+        offset = 0;
+      }
     }
   }