Tweak Generate_InterpreterEntryTrampoline code

Small improvements to code generated on arm and arm64.

Bug: v8:6644
Change-Id: Id3d9be87f6a071e949985a1b6b62a43d9195a104
Reviewed-on: https://chromium-review.googlesource.com/615300Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Martyn Capewell <martyn.capewell@arm.com>
Cr-Commit-Position: refs/heads/master@{#47359}

src/builtins/arm/builtins-arm.cc

@@ -1207,14 +1207,11 @@ void Builtins::Generate_InterpreterEntryTrampoline(MacroAssembler* masm) {
 
   // If the bytecode array has a valid incoming new target or generator object
   // register, initialize it with incoming value which was passed in r3.
-  Label no_incoming_new_target_or_generator_register;
   __ ldr(r9, FieldMemOperand(
                  kInterpreterBytecodeArrayRegister,
                  BytecodeArray::kIncomingNewTargetOrGeneratorRegisterOffset));
-  __ tst(r9, r9);
-  __ b(eq, &no_incoming_new_target_or_generator_register);
-  __ str(r3, MemOperand(fp, r9, LSL, kPointerSizeLog2));
-  __ bind(&no_incoming_new_target_or_generator_register);
+  __ cmp(r9, Operand::Zero());
+  __ str(r3, MemOperand(fp, r9, LSL, kPointerSizeLog2), ne);
 
   // Load accumulator and dispatch table into registers.
   __ LoadRoot(kInterpreterAccumulatorRegister, Heap::kUndefinedValueRootIndex);

src/builtins/arm64/builtins-arm64.cc

@@ -1227,8 +1227,7 @@ void Builtins::Generate_InterpreterEntryTrampoline(MacroAssembler* masm) {
            FieldMemOperand(
                kInterpreterBytecodeArrayRegister,
                BytecodeArray::kIncomingNewTargetOrGeneratorRegisterOffset));
-  __ Tst(x10, x10);
-  __ B(eq, &no_incoming_new_target_or_generator_register);
+  __ Cbz(x10, &no_incoming_new_target_or_generator_register);
   __ Str(x3, MemOperand(fp, x10, LSL, kPointerSizeLog2));
   __ Bind(&no_incoming_new_target_or_generator_register);
 
@@ -1254,8 +1253,7 @@ void Builtins::Generate_InterpreterEntryTrampoline(MacroAssembler* masm) {
   // kInterpreterBytecodeArrayRegister is already loaded with
   // SharedFunctionInfo::kFunctionDataOffset.
   __ Bind(&maybe_load_debug_bytecode_array);
-  __ Ldr(x10, FieldMemOperand(x11, DebugInfo::kFlagsOffset));
-  __ SmiUntag(x10);
+  __ Ldrsw(x10, UntagSmiFieldMemOperand(x11, DebugInfo::kFlagsOffset));
   __ TestAndBranchIfAllClear(x10, DebugInfo::kHasBreakInfo,
                              &bytecode_array_loaded);
   __ Ldr(kInterpreterBytecodeArrayRegister,