1 files changed, 20 insertions, 0 deletions
diff --git a/src/ast/bits.h b/src/ast/bits.h
index d88cb5edb..11cf7b06d 100644
--- a/src/ast/bits.h
+++ b/src/ast/bits.h
@@ -39,6 +39,26 @@ struct Bits {
     // this is indeed a mask
     return 32 - CountLeadingZeroes(mask);
   }
+
+  // gets the number of effective shifts a shift operation does. In
+  // wasm, only 5 bits matter for 32-bit shifts, and 6 for 64.
+  static Index getEffectiveShifts(Index amount, WasmType type) {
+    if (type == i32) {
+      return amount & 31;
+    } else if (type == i64) {
+      return amount & 63;
+    }
+    WASM_UNREACHABLE();
+  }
+
+  static Index getEffectiveShifts(Const* amount) {
+    if (amount->type == i32) {
+      return getEffectiveShifts(amount->value.geti32(), i32);
+    } else if (amount->type == i64) {
+      return getEffectiveShifts(amount->value.geti64(), i64);
+    }
+    WASM_UNREACHABLE();
+  }
 };
 
 } // namespace wasm