Сonstant value truncation during store operation (#3117)

1 files changed, 13 insertions, 0 deletions

diff --git a/src/passes/OptimizeInstructions.cpp b/src/passes/OptimizeInstructions.cpp
index 982f99a04..0ce1f5f95 100644
--- a/src/passes/OptimizeInstructions.cpp
+++ b/src/passes/OptimizeInstructions.cpp
@@ -826,6 +826,19 @@ struct OptimizeInstructions
       optimizeMemoryAccess(load->ptr, load->offset);
     } else if (auto* store = curr->dynCast<Store>()) {
       optimizeMemoryAccess(store->ptr, store->offset);
+      if (store->valueType.isInteger()) {
+        // truncates constant values during stores
+        // (i32|i64).store(8|16|32)(p, C)   ==>
+        //    (i32|i64).store(8|16|32)(p, C & mask)
+        if (auto* c = store->value->dynCast<Const>()) {
+          if (store->valueType == Type::i64 && store->bytes == 4) {
+            c->value = c->value.and_(Literal(uint64_t(0xffffffff)));
+          } else {
+            c->value = c->value.and_(Literal::makeFromInt32(
+              Bits::lowBitMask(store->bytes * 8), store->valueType));
+          }
+        }
+      }
       // stores of fewer bits truncates anyhow
       if (auto* binary = store->value->dynCast<Binary>()) {
         if (binary->op == AndInt32) {