X64: Use allocation with no scratch registers to avoid push/pop.

src/x64/macro-assembler-x64.cc

 // Copyright 2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2338 matching lines @@
     ASSERT(!scratch.is_valid());
 #ifdef DEBUG
     // Assert that result actually contains top on entry.
     movq(kScratchRegister, new_space_allocation_top);
     cmpq(result, Operand(kScratchRegister, 0));
     Check(equal, "Unexpected allocation top");
 #endif
     return;
   }
 
-  // Move address of new object to result. Use scratch register if available.
-  if (!scratch.is_valid()) {
-    if (result.is(rax)) {
-      load_rax(new_space_allocation_top);
-    } else {
-      movq(kScratchRegister, new_space_allocation_top);
-      movq(result, Operand(kScratchRegister, 0));
-    }
-  } else {
+  // Move address of new object to result. Use scratch register if available,
+  // and keep address in scratch until call to UpdateAllocationTopHelper.
+  if (scratch.is_valid()) {
     ASSERT(!scratch.is(result_end));
     movq(scratch, new_space_allocation_top);
     movq(result, Operand(scratch, 0));
+  } else if (result.is(rax)) {
+    load_rax(new_space_allocation_top);
+  } else {
+    movq(kScratchRegister, new_space_allocation_top);
+    movq(result, Operand(kScratchRegister, 0));
   }
 }
 
 
 void MacroAssembler::UpdateAllocationTopHelper(Register result_end,
                                                Register scratch) {
   if (FLAG_debug_code) {
     testq(result_end, Immediate(kObjectAlignmentMask));
     Check(zero, "Unaligned allocation in new space");
   }
 
   ExternalReference new_space_allocation_top =
       ExternalReference::new_space_allocation_top_address();
 
   // Update new top.
   if (result_end.is(rax)) {
     // rax can be stored directly to a memory location.
     store_rax(new_space_allocation_top);
   } else {
     // Register required - use scratch provided if available.
-    if (!scratch.is_valid()) {
+    if (scratch.is_valid()) {
+      movq(Operand(scratch, 0), result_end);
+    } else {
       movq(kScratchRegister, new_space_allocation_top);
       movq(Operand(kScratchRegister, 0), result_end);
-    } else {
-      movq(Operand(scratch, 0), result_end);
     }
   }
 }
 
 
 void MacroAssembler::AllocateInNewSpace(int object_size,
                                         Register result,
                                         Register result_end,
                                         Register scratch,
                                         Label* gc_required,
                                         AllocationFlags flags) {
   ASSERT(!result.is(result_end));
 
   // Load address of new object into result.
   LoadAllocationTopHelper(result, result_end, scratch, flags);
 
   // Calculate new top and bail out if new space is exhausted.
   ExternalReference new_space_allocation_limit =
       ExternalReference::new_space_allocation_limit_address();
 
   Register top_reg = result_end.is_valid() ? result_end : result;
 
-  lea(top_reg, Operand(result, object_size));
+  if (top_reg.is(result)) {
+    addq(top_reg, Immediate(object_size));
+  } else {
+    lea(top_reg, Operand(result, object_size));
+  }
   movq(kScratchRegister, new_space_allocation_limit);
   cmpq(top_reg, Operand(kScratchRegister, 0));
   j(above, gc_required);
 
   // Update allocation top.
   UpdateAllocationTopHelper(top_reg, scratch);
 
   if (top_reg.is(result)) {
     if ((flags & TAG_OBJECT) != 0) {
       subq(result, Immediate(object_size - kHeapObjectTag));
@@ skipping 283 matching lines @@
 CodePatcher::~CodePatcher() {
   // Indicate that code has changed.
   CPU::FlushICache(address_, size_);
 
   // Check that the code was patched as expected.
   ASSERT(masm_.pc_ == address_ + size_);
   ASSERT(masm_.reloc_info_writer.pos() == address_ + size_ + Assembler::kGap);
 }
 
 } }  // namespace v8::internal