3 files changed, 19 insertions, 1 deletions
diff --git a/src/passes/OptimizeInstructions.cpp b/src/passes/OptimizeInstructions.cpp
index 43a8faa32..2a77b408a 100644
--- a/src/passes/OptimizeInstructions.cpp
+++ b/src/passes/OptimizeInstructions.cpp
@@ -188,7 +188,7 @@ 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) + (shifts->value.geti32() & 31));
         }
         return 32;
       }
diff --git a/test/passes/optimize-instructions.txt b/test/passes/optimize-instructions.txt
index 68359d9fb..f7948860c 100644
--- a/test/passes/optimize-instructions.txt
+++ b/test/passes/optimize-instructions.txt
@@ -2015,4 +2015,13 @@
    (i32.const 255)
   )
  )
+ (func $neg-shifts-and-255-b (type $2) (result i32)
+  (i32.and
+   (i32.shl
+    (i32.const -2349025)
+    (i32.const -32)
+   )
+   (i32.const 255)
+  )
+ )
 )
diff --git a/test/passes/optimize-instructions.wast b/test/passes/optimize-instructions.wast
index 5300b8da8..107451b87 100644
--- a/test/passes/optimize-instructions.wast
+++ b/test/passes/optimize-instructions.wast
@@ -2442,4 +2442,13 @@
      (i32.const 255)
     )
   )
+  (func $neg-shifts-and-255-b (result i32)
+   (i32.and
+    (i32.shl
+     (i32.const -2349025)
+     (i32.const -32) ;; this shift does nothing
+    )
+    (i32.const 255)
+   )
+  )
 )