PPC: Resolve references to "this" the same way as normal variables

Port bd56d279

Original commit message:
Make the parser handle references to "this" as unresolved variables, so the
same logic as for the rest of function parameters is used for the receiver.
Minor additions to the code generation handle copying the receiver to the
context, along with the rest of the function parameters.

Based on work by Adrian Perez de Castro <aperez@igalia.com>.

This is a reapplication of https://codereview.chromium.org/1130733003.

R=wingo@igalia.com, dstence@us.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1134073003

Cr-Commit-Position: refs/heads/master@{#28342}

src/ppc/full-codegen-ppc.cc

@@ -124,7 +124,7 @@ void FullCodeGenerator::Generate() {
   // global proxy when called as functions (without an explicit receiver
   // object).
   if (is_sloppy(info->language_mode()) && !info->is_native() &&
-      info->MayUseThis()) {
+      info->MayUseThis() && info->scope()->has_this_declaration()) {
     Label ok;
     int receiver_offset = info->scope()->num_parameters() * kPointerSize;
     __ LoadP(r5, MemOperand(sp, receiver_offset), r0);
@@ -221,8 +221,9 @@ void FullCodeGenerator::Generate() {
     __ StoreP(r3, MemOperand(fp, StandardFrameConstants::kContextOffset));
     // Copy any necessary parameters into the context.
     int num_parameters = info->scope()->num_parameters();
-    for (int i = 0; i < num_parameters; i++) {
-      Variable* var = scope()->parameter(i);
+    int first_parameter = info->scope()->has_this_declaration() ? -1 : 0;
+    for (int i = first_parameter; i < num_parameters; i++) {
+      Variable* var = (i == -1) ? scope()->receiver() : scope()->parameter(i);
       if (var->IsContextSlot()) {
         int parameter_offset = StandardFrameConstants::kCallerSPOffset +
                                (num_parameters - 1 - i) * kPointerSize;
@@ -3049,8 +3050,9 @@ void FullCodeGenerator::EmitResolvePossiblyDirectEval(int arg_count) {
   __ LoadP(r7, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
 
   // r6: the receiver of the enclosing function.
-  int receiver_offset = 2 + info_->scope()->num_parameters();
-  __ LoadP(r6, MemOperand(fp, receiver_offset * kPointerSize), r0);
+  Variable* this_var = scope()->LookupThis();
+  DCHECK_NOT_NULL(this_var);
+  GetVar(r6, this_var);
 
   // r5: language mode.
   __ LoadSmiLiteral(r5, Smi::FromInt(language_mode()));

src/ppc/lithium-codegen-ppc.cc

@@ -118,8 +118,8 @@ bool LCodeGen::GeneratePrologue() {
     // Sloppy mode functions and builtins need to replace the receiver with the
     // global proxy when called as functions (without an explicit receiver
     // object).
-    if (is_sloppy(info_->language_mode()) && info()->MayUseThis() &&
-        !info_->is_native()) {
+    if (is_sloppy(info_->language_mode()) && info_->MayUseThis() &&
+        !info_->is_native() && info_->scope()->has_this_declaration()) {
       Label ok;
       int receiver_offset = info_->scope()->num_parameters() * kPointerSize;
       __ LoadP(r5, MemOperand(sp, receiver_offset));
@@ -199,8 +199,9 @@ bool LCodeGen::GeneratePrologue() {
     __ StoreP(r3, MemOperand(fp, StandardFrameConstants::kContextOffset));
     // Copy any necessary parameters into the context.
     int num_parameters = scope()->num_parameters();
-    for (int i = 0; i < num_parameters; i++) {
-      Variable* var = scope()->parameter(i);
+    int first_parameter = scope()->has_this_declaration() ? -1 : 0;
+    for (int i = first_parameter; i < num_parameters; i++) {
+      Variable* var = (i == -1) ? scope()->receiver() : scope()->parameter(i);
       if (var->IsContextSlot()) {
         int parameter_offset = StandardFrameConstants::kCallerSPOffset +
                                (num_parameters - 1 - i) * kPointerSize;