[crankshaft] do not restore rsi in stub for deferred number conversions

src/crankshaft/x87/lithium-codegen-x87.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_X87
 
 #include "src/crankshaft/x87/lithium-codegen-x87.h"
 
 #include "src/base/bits.h"
 #include "src/code-factory.h"
@@ skipping 4593 matching lines @@
   // 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.
     __ Move(reg, Immediate(0));
 
     // 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));
+    // Reset the context register.
+    if (!reg.is(esi)) {
+      __ Move(esi, Immediate(0));
+    }
     __ CallRuntimeSaveDoubles(Runtime::kAllocateHeapNumber);
     RecordSafepointWithRegisters(
         instr->pointer_map(), 0, Safepoint::kNoLazyDeopt);
     __ StoreToSafepointRegisterSlot(reg, eax);
   }
 
   __ bind(&done);
   __ fstp_d(FieldOperand(reg, HeapNumber::kValueOffset));
 }
 
@@ skipping 34 matching lines @@
 
 
 void LCodeGen::DoDeferredNumberTagD(LNumberTagD* instr) {
   // TODO(3095996): Get rid of this. For now, we need to make the
   // result register contain a valid pointer because it is already
   // contained in the register pointer map.
   Register reg = ToRegister(instr->result());
   __ Move(reg, Immediate(0));
 
   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));
+  // Reset the context register.
+  if (!reg.is(esi)) {
+    __ Move(esi, Immediate(0));
+  }
   __ CallRuntimeSaveDoubles(Runtime::kAllocateHeapNumber);
   RecordSafepointWithRegisters(
       instr->pointer_map(), 0, Safepoint::kNoLazyDeopt);
   __ StoreToSafepointRegisterSlot(reg, eax);
 }
 
 
 void LCodeGen::DoSmiTag(LSmiTag* instr) {
   HChange* hchange = instr->hydrogen();
   Register input = ToRegister(instr->value());
@@ skipping 1088 matching lines @@
   __ bind(deferred->exit());
   __ bind(&done);
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X87