fix optimize-instructions handling of shifts by a zero or of a zero when combining added constants (#1206)

1 files changed, 3 insertions, 2 deletions

diff --git a/src/passes/OptimizeInstructions.cpp b/src/passes/OptimizeInstructions.cpp
index ad667f888..cdfa29138 100644
--- a/src/passes/OptimizeInstructions.cpp
+++ b/src/passes/OptimizeInstructions.cpp
@@ -862,8 +862,9 @@ private:
             return;
           }
         } else if (curr->op == ShlInt32) {
-          // shifting a 0 is a 0, unless the shift has side effects
-          if (left && Bits::getEffectiveShifts(left) == 0 && !EffectAnalyzer(passOptions, curr->right).hasSideEffects()) {
+          // shifting a 0 is a 0, or anything by 0 has no effect, all unless the shift has side effects
+          if (((left && left->value.geti32() == 0) || (right && Bits::getEffectiveShifts(right) == 0)) &&
+              !EffectAnalyzer(passOptions, curr->right).hasSideEffects()) {
             replaceCurrent(left);
             return;
           }