MIPS64: VectorICs: keyed element loads were kicking out non-smi keys unnecessarily

Port 6689cc27

Original commit message:
Handlers should be in charge of this work. The change uncovered a bug in
vector-ics related to keyed loads into strings. It's important for
StringCharCodeAtGenerator, a helper used in full code and in
LoadIndexedStringStub (a handler) to protect the vector and slot registers
when it makes a runtime call to convert a HeapNumber to a Smi.

It's still possible for the handler to MISS after this call, perhaps due
to out of bounds access. In that case, the vector and slot registers need
to be delivered safely to the MISS handler.

BUG=

Review URL: https://codereview.chromium.org/1025303005

Cr-Commit-Position: refs/heads/master@{#27383}

src/mips64/code-stubs-mips64.cc

@@ -1380,12 +1380,8 @@ void LoadIndexedStringStub::Generate(MacroAssembler* masm) {
   Register result = v0;
   DCHECK(!scratch.is(receiver) && !scratch.is(index));
   DCHECK(!FLAG_vector_ics ||
-         (!scratch.is(VectorLoadICDescriptor::VectorRegister()) &&
-          result.is(VectorLoadICDescriptor::SlotRegister())));
+         !scratch.is(VectorLoadICDescriptor::VectorRegister()));
 
-  // StringCharAtGenerator doesn't use the result register until it's passed
-  // the different miss possibilities. If it did, we would have a conflict
-  // when FLAG_vector_ics is true.
   StringCharAtGenerator char_at_generator(receiver, index, scratch, result,
                                           &miss,  // When not a string.
                                           &miss,  // When not a number.
@@ -1396,7 +1392,7 @@ void LoadIndexedStringStub::Generate(MacroAssembler* masm) {
   __ Ret();
 
   StubRuntimeCallHelper call_helper;
-  char_at_generator.GenerateSlow(masm, call_helper);
+  char_at_generator.GenerateSlow(masm, PART_OF_IC_HANDLER, call_helper);
 
   __ bind(&miss);
   PropertyAccessCompiler::TailCallBuiltin(
@@ -3089,7 +3085,7 @@ void CallICStub::GenerateMiss(MacroAssembler* masm) {
 
 
 void StringCharCodeAtGenerator::GenerateSlow(
-    MacroAssembler* masm,
+    MacroAssembler* masm, EmbedMode embed_mode,
     const RuntimeCallHelper& call_helper) {
   __ Abort(kUnexpectedFallthroughToCharCodeAtSlowCase);
 
@@ -3103,7 +3099,12 @@ void StringCharCodeAtGenerator::GenerateSlow(
               DONT_DO_SMI_CHECK);
   call_helper.BeforeCall(masm);
   // Consumed by runtime conversion function:
-  __ Push(object_, index_);
+  if (FLAG_vector_ics && embed_mode == PART_OF_IC_HANDLER) {
+    __ Push(VectorLoadICDescriptor::VectorRegister(),
+            VectorLoadICDescriptor::SlotRegister(), object_, index_);
+  } else {
+    __ Push(object_, index_);
+  }
   if (index_flags_ == STRING_INDEX_IS_NUMBER) {
     __ CallRuntime(Runtime::kNumberToIntegerMapMinusZero, 1);
   } else {
@@ -3116,7 +3117,12 @@ void StringCharCodeAtGenerator::GenerateSlow(
   // have a chance to overwrite it.
 
   __ Move(index_, v0);
-  __ pop(object_);
+  if (FLAG_vector_ics && embed_mode == PART_OF_IC_HANDLER) {
+    __ Pop(VectorLoadICDescriptor::SlotRegister(),
+           VectorLoadICDescriptor::VectorRegister(), object_);
+  } else {
+    __ pop(object_);
+  }
   // Reload the instance type.
   __ ld(result_, FieldMemOperand(object_, HeapObject::kMapOffset));
   __ lbu(result_, FieldMemOperand(result_, Map::kInstanceTypeOffset));

src/mips64/full-codegen-mips64.cc

@@ -4111,7 +4111,7 @@ void FullCodeGenerator::EmitStringCharCodeAt(CallRuntime* expr) {
   __ jmp(&done);
 
   NopRuntimeCallHelper call_helper;
-  generator.GenerateSlow(masm_, call_helper);
+  generator.GenerateSlow(masm_, NOT_PART_OF_IC_HANDLER, call_helper);
 
   __ bind(&done);
   context()->Plug(result);
@@ -4160,7 +4160,7 @@ void FullCodeGenerator::EmitStringCharAt(CallRuntime* expr) {
   __ jmp(&done);
 
   NopRuntimeCallHelper call_helper;
-  generator.GenerateSlow(masm_, call_helper);
+  generator.GenerateSlow(masm_, NOT_PART_OF_IC_HANDLER, call_helper);
 
   __ bind(&done);
   context()->Plug(result);