Bug 1628836: Add missing JSOp::Pow case for string-int32 arithmetic in CacheIR. r=jandem

Differential Revision: https://phabricator.services.mozilla.com/D70807

--HG--
extra : moz-landing-system : lando

js/src/jit-test/tests/cacheir/string-int32-arith.js

@@ -13,6 +13,9 @@ function test(zero, one) {
     assertEq(one / 1, 1);
     assertEq(10 % one, 0);
     assertEq(one % 1, 0);
+
+    assertEq(10 ** one, 10);
+    assertEq(one ** 4, 1);
 }
 
 for (var i = 0; i < 10; i++) {

js/src/jit/CacheIR.cpp

@@ -7036,6 +7036,10 @@ AttachDecision BinaryArithIRGenerator::tryAttachStringInt32Arith() {
       writer.int32ModResult(lhsIntId, rhsIntId);
       trackAttached("BinaryArith.StringInt32.Mod");
       break;
+    case JSOp::Pow:
+      writer.int32PowResult(lhsIntId, rhsIntId);
+      trackAttached("BinaryArith.StringInt32.Pow");
+      break;
     default:
       MOZ_CRASH("Unhandled op in tryAttachStringInt32Arith");
   }