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

src/arm/lithium-codegen-arm.cc

Index: src/arm/lithium-codegen-arm.cc
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index 51126db7aae9550ba99f20a889b930b541ae8d47..651f3f19add8fcbaf779402571230fba0285fc38 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -4599,9 +4599,11 @@ void LCodeGen::DoNumberTagI(LNumberTagI* instr) {
     DeferredNumberTagI(LCodeGen* codegen, LNumberTagI* instr)
         : LDeferredCode(codegen), instr_(instr) { }
     virtual void Generate() V8_OVERRIDE {
-      codegen()->DoDeferredNumberTagI(instr_,
-                                      instr_->value(),
-                                      SIGNED_INT32);
+      codegen()->DoDeferredNumberTagIU(instr_,
+                                       instr_->value(),
+                                       instr_->temp1(),
+                                       instr_->temp2(),
+                                       SIGNED_INT32);
     }
     virtual LInstruction* instr() V8_OVERRIDE { return instr_; }
    private:
@@ -4624,9 +4626,11 @@ void LCodeGen::DoNumberTagU(LNumberTagU* instr) {
     DeferredNumberTagU(LCodeGen* codegen, LNumberTagU* instr)
         : LDeferredCode(codegen), 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:
@@ -4644,18 +4648,19 @@ 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 src = ToRegister(value);
   Register dst = ToRegister(instr->result());
+  Register tmp1 = scratch0();
+  Register tmp2 = ToRegister(temp1);
+  Register tmp3 = ToRegister(temp2);
   LowDwVfpRegister dbl_scratch = double_scratch0();
 
-  // Preserve the value of all registers.
-  PushSafepointRegistersScope scope(this, Safepoint::kWithRegisters);
-
-  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
@@ -4672,38 +4677,40 @@ void LCodeGen::DoDeferredNumberTagI(LInstruction* instr,
   }
 
   if (FLAG_inline_new) {
-    __ LoadRoot(scratch0(), Heap::kHeapNumberMapRootIndex);
-    __ AllocateHeapNumber(r5, r3, r4, scratch0(), &slow, DONT_TAG_RESULT);
-    __ Move(dst, r5);
+    __ LoadRoot(tmp3, Heap::kHeapNumberMapRootIndex);
+    __ AllocateHeapNumber(dst, tmp1, tmp2, tmp3, &slow, DONT_TAG_RESULT);
     __ b(&done);
   }
 
   // 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.
+    __ mov(dst, Operand::Zero());
 
-  // 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.
-  __ mov(ip, Operand::Zero());
-  __ StoreToSafepointRegisterSlot(ip, dst);
-  // 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.
-  __ ldr(cp, MemOperand(fp, StandardFrameConstants::kContextOffset));
-  __ CallRuntimeSaveDoubles(Runtime::kAllocateHeapNumber);
-  RecordSafepointWithRegisters(
-      instr->pointer_map(), 0, Safepoint::kNoLazyDeopt);
-  __ Move(dst, r0);
-  __ sub(dst, dst, Operand(kHeapObjectTag));
+    // Preserve the value of all registers.
+    PushSafepointRegistersScope scope(this, Safepoint::kWithRegisters);
+
+    // 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.
+    __ ldr(cp, MemOperand(fp, StandardFrameConstants::kContextOffset));
+    __ CallRuntimeSaveDoubles(Runtime::kAllocateHeapNumber);
+    RecordSafepointWithRegisters(
+        instr->pointer_map(), 0, Safepoint::kNoLazyDeopt);
+    __ sub(r0, r0, Operand(kHeapObjectTag));
+    __ StoreToSafepointRegisterSlot(r0, dst);
+  }
 
   // Done. Put the value in dbl_scratch into the value of the allocated heap
   // number.
   __ bind(&done);
   __ vstr(dbl_scratch, dst, HeapNumber::kValueOffset);
   __ add(dst, dst, Operand(kHeapObjectTag));
-  __ StoreToSafepointRegisterSlot(dst, dst);
 }