Push safepoint registers in deferred number-to-i/u only on-demand.

src/ia32/lithium-codegen-ia32.cc

Index: src/ia32/lithium-codegen-ia32.cc
diff --git a/src/ia32/lithium-codegen-ia32.cc b/src/ia32/lithium-codegen-ia32.cc
index ed5bd47a403101735846ab11fefd8e08fa670594..4732f162872ad030e06b68f145085d31225f8bbc 100644
--- a/src/ia32/lithium-codegen-ia32.cc
+++ b/src/ia32/lithium-codegen-ia32.cc
@@ -4897,7 +4897,8 @@ void LCodeGen::DoNumberTagI(LNumberTagI* instr) {
                        const X87Stack& x87_stack)
         : LDeferredCode(codegen, x87_stack), instr_(instr) { }
     virtual void Generate() V8_OVERRIDE {
-      codegen()->DoDeferredNumberTagI(instr_, instr_->value(), SIGNED_INT32);
+      codegen()->DoDeferredNumberTagIU(instr_, instr_->value(), instr_->temp(),
+                                       NULL, SIGNED_INT32);
     }
     virtual LInstruction* instr() V8_OVERRIDE { return instr_; }
    private:
@@ -4924,7 +4925,8 @@ void LCodeGen::DoNumberTagU(LNumberTagU* instr) {
                        const X87Stack& x87_stack)
         : LDeferredCode(codegen, x87_stack), instr_(instr) { }
     virtual void Generate() V8_OVERRIDE {
-      codegen()->DoDeferredNumberTagI(instr_, instr_->value(), UNSIGNED_INT32);
+      codegen()->DoDeferredNumberTagIU(instr_, instr_->value(), instr_->temp1(),
+                                       instr_->temp2(), UNSIGNED_INT32);
     }
     virtual LInstruction* instr() V8_OVERRIDE { return instr_; }
    private:
@@ -4944,19 +4946,16 @@ void LCodeGen::DoNumberTagU(LNumberTagU* instr) {
 }
 
 
-void LCodeGen::DoDeferredNumberTagI(LInstruction* instr,
-                                    LOperand* value,
-                                    IntegerSignedness signedness) {
-  Label slow;
+void LCodeGen::DoDeferredNumberTagIU(LInstruction* instr,
+                                     LOperand* value,
+                                     LOperand* temp1,
+                                     LOperand* temp2,
+                                     IntegerSignedness signedness) {
+  Label done, slow;
   Register reg = ToRegister(value);
-  Register tmp = reg.is(eax) ? ecx : eax;
+  Register tmp = ToRegister(temp1);
   XMMRegister xmm_scratch = double_scratch0();
 
-  // Preserve the value of all registers.
-  PushSafepointRegistersScope scope(this);
-
-  Label done;
-
   if (signedness == SIGNED_INT32) {
     // There was overflow, so bits 30 and 31 of the original integer
     // disagree. Try to allocate a heap number in new space and store
@@ -4974,8 +4973,7 @@ void LCodeGen::DoDeferredNumberTagI(LInstruction* instr,
   } else {
     if (CpuFeatures::IsSupported(SSE2)) {
       CpuFeatureScope feature_scope(masm(), SSE2);
-      __ LoadUint32(xmm_scratch, reg,
-                    ToDoubleRegister(LNumberTagU::cast(instr)->temp()));
+      __ LoadUint32(xmm_scratch, reg, ToDoubleRegister(temp2));
     } else {
       // There's no fild variant for unsigned values, so zero-extend to a 64-bit
       // int manually.
@@ -4994,21 +4992,26 @@ void LCodeGen::DoDeferredNumberTagI(LInstruction* instr,
 
   // Slow case: Call the runtime system to do the number allocation.
   __ bind(&slow);
+  {
+    // TODO(3095996): Put a valid pointer value in the stack slot where the
+    // result register is stored, as this register is in the pointer map, but
+    // contains an integer value.
+    __ Set(reg, Immediate(0));
 
-  // TODO(3095996): Put a valid pointer value in the stack slot where the result
-  // register is stored, as this register is in the pointer map, but contains an
-  // integer value.
-  __ StoreToSafepointRegisterSlot(reg, Immediate(0));
-  // NumberTagI and NumberTagD use the context from the frame, rather than
-  // the environment's HContext or HInlinedContext value.
-  // They only call Runtime::kAllocateHeapNumber.
-  // The corresponding HChange instructions are added in a phase that does
-  // not have easy access to the local context.
-  __ mov(esi, Operand(ebp, StandardFrameConstants::kContextOffset));
-  __ CallRuntimeSaveDoubles(Runtime::kAllocateHeapNumber);
-  RecordSafepointWithRegisters(
-      instr->pointer_map(), 0, Safepoint::kNoLazyDeopt);
-  if (!reg.is(eax)) __ mov(reg, eax);
+    // Preserve the value of all registers.
+    PushSafepointRegistersScope scope(this);
+
+    // NumberTagI and NumberTagD use the context from the frame, rather than
+    // the environment's HContext or HInlinedContext value.
+    // They only call Runtime::kAllocateHeapNumber.
+    // The corresponding HChange instructions are added in a phase that does
+    // not have easy access to the local context.
+    __ mov(esi, Operand(ebp, StandardFrameConstants::kContextOffset));
+    __ CallRuntimeSaveDoubles(Runtime::kAllocateHeapNumber);
+    RecordSafepointWithRegisters(
+        instr->pointer_map(), 0, Safepoint::kNoLazyDeopt);
+    __ StoreToSafepointRegisterSlot(reg, eax);
+  }
 
   // Done. Put the value in xmm_scratch into the value of the allocated heap
   // number.
@@ -5019,7 +5022,6 @@ void LCodeGen::DoDeferredNumberTagI(LInstruction* instr,
   } else {
     __ fstp_d(FieldOperand(reg, HeapNumber::kValueOffset));
   }
-  __ StoreToSafepointRegisterSlot(reg, reg);
 }