PPC: [turbofan] Frame elision for code stubs.

src/compiler/ppc/code-generator-ppc.cc

Index: src/compiler/ppc/code-generator-ppc.cc
diff --git a/src/compiler/ppc/code-generator-ppc.cc b/src/compiler/ppc/code-generator-ppc.cc
index d827dead815eca3e4691160460dcca76fbc8a2a6..5acdcab24d32d729f2733388aab35166da46af7c 100644
--- a/src/compiler/ppc/code-generator-ppc.cc
+++ b/src/compiler/ppc/code-generator-ppc.cc
@@ -187,7 +187,8 @@ class OutOfLineRecordWrite final : public OutOfLineCode {
         value_(value),
         scratch0_(scratch0),
         scratch1_(scratch1),
-        mode_(mode) {}
+        mode_(mode),
+        must_save_lr_(!gen->frame_access_state()->has_frame()) {}
 
   void Generate() final {
     if (mode_ > RecordWriteMode::kValueIsPointer) {
@@ -201,7 +202,7 @@ class OutOfLineRecordWrite final : public OutOfLineCode {
                                              : OMIT_REMEMBERED_SET;
     SaveFPRegsMode const save_fp_mode =
         frame()->DidAllocateDoubleRegisters() ? kSaveFPRegs : kDontSaveFPRegs;
-    if (!frame()->needs_frame()) {
+    if (must_save_lr_) {
       // We need to save and restore lr if the frame was elided.
       __ mflr(scratch1_);
       __ Push(scratch1_);
@@ -215,7 +216,7 @@ class OutOfLineRecordWrite final : public OutOfLineCode {
       __ add(scratch1_, object_, offset_);
     }
     __ CallStub(&stub);
-    if (!frame()->needs_frame()) {
+    if (must_save_lr_) {
       // We need to save and restore lr if the frame was elided.
       __ Pop(scratch1_);
       __ mtlr(scratch1_);
@@ -230,6 +231,7 @@ class OutOfLineRecordWrite final : public OutOfLineCode {
   Register const scratch0_;
   Register const scratch1_;
   RecordWriteMode const mode_;
+  bool must_save_lr_;
 };
 
 
@@ -670,6 +672,11 @@ Condition FlagsConditionToCondition(FlagsCondition condition, ArchOpcode op) {
     DCHECK_EQ(LeaveRC, i.OutputRCBit());                      \
   } while (0)
 
+void CodeGenerator::AssembleDeconstructFrame() {
+  __ LeaveFrame(StackFrame::MANUAL);
+}
+
+void CodeGenerator::AssembleSetupStackPointer() {}
 
 void CodeGenerator::AssembleDeconstructActivationRecord(int stack_param_delta) {
   int sp_slot_delta = TailCallFrameStackSlotDelta(stack_param_delta);
@@ -686,7 +693,7 @@ void CodeGenerator::AssemblePrepareTailCall(int stack_param_delta) {
     __ Add(sp, sp, sp_slot_delta * kPointerSize, r0);
     frame_access_state()->IncreaseSPDelta(-sp_slot_delta);
   }
-  if (frame()->needs_frame()) {
+  if (frame_access_state()->has_frame()) {
     __ RestoreFrameStateForTailCall();
   }
   frame_access_state()->SetFrameAccessToSP();
@@ -867,7 +874,7 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       DCHECK_EQ(LeaveRC, i.OutputRCBit());
       break;
     case kArchParentFramePointer:
-      if (frame_access_state()->frame()->needs_frame()) {
+      if (frame_access_state()->has_frame()) {
         __ LoadP(i.OutputRegister(), MemOperand(fp, 0));
       } else {
         __ mr(i.OutputRegister(), fp);
@@ -1695,7 +1702,7 @@ void CodeGenerator::AssembleDeoptimizerCall(
 
 void CodeGenerator::AssemblePrologue() {
   CallDescriptor* descriptor = linkage()->GetIncomingDescriptor();
-  if (frame()->needs_frame()) {
+  if (frame_access_state()->has_frame()) {
     if (descriptor->IsCFunctionCall()) {
       __ function_descriptor();
       __ mflr(r0);
@@ -1711,18 +1718,11 @@ void CodeGenerator::AssemblePrologue() {
       __ Prologue(this->info()->GeneratePreagedPrologue(), ip);
     } else {
       StackFrame::Type type = info()->GetOutputStackFrameType();
-      if (!ABI_CALL_VIA_IP &&
-          info()->output_code_kind() == Code::WASM_FUNCTION) {
-        // TODO(mbrandy): Restrict only to the wasm wrapper case.
-        __ StubPrologue(type);
-      } else {
-        __ StubPrologue(type, ip);
-      }
+      // TODO(mbrandy): Detect cases where ip is the entrypoint (for
+      // efficient intialization of the constant pool pointer register).
+      __ StubPrologue(type);
     }
-  } else {
-    frame()->SetElidedFrameSizeInSlots(0);
   }
-  frame_access_state()->SetFrameAccessToDefault();
 
   int stack_shrink_slots = frame()->GetSpillSlotCount();
   if (info()->is_osr()) {
@@ -1791,20 +1791,18 @@ void CodeGenerator::AssembleReturn() {
   }
 
   if (descriptor->IsCFunctionCall()) {
-    __ LeaveFrame(StackFrame::MANUAL, pop_count * kPointerSize);
-  } else if (frame()->needs_frame()) {
+    AssembleDeconstructFrame();
+  } else if (frame_access_state()->has_frame()) {
     // Canonicalize JSFunction return sites for now.
     if (return_label_.is_bound()) {
       __ b(&return_label_);
       return;
     } else {
       __ bind(&return_label_);
-      __ LeaveFrame(StackFrame::MANUAL, pop_count * kPointerSize);
+      AssembleDeconstructFrame();
     }
-  } else {
-    __ Drop(pop_count);

[Mircea Trofin, 2016/03/30 22:39:24]

What happened to the pop_count?

[MTBrandyberry, 2016/03/30 22:57:47]

Since we can no longer can pass it via AssembleDeconstructFrame to Leaveframe,
the adjustment is done in all cases by Ret below.

   }
-  __ Ret();
+  __ Ret(pop_count);
 }