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

src/crankshaft/x64/lithium-codegen-x64.cc

 // Copyright 2013 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_X64
 
 #include "src/crankshaft/x64/lithium-codegen-x64.h"
 
 #include "src/base/bits.h"
 #include "src/code-factory.h"
@@ skipping 4537 matching lines @@
   // Slow case: Call the runtime system to do the number allocation.
   __ bind(&slow);
   {
     // 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, 0);
 
     // Preserve the value of all registers.
     PushSafepointRegistersScope scope(this);
-
-    // NumberTagIU uses 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.
-    __ movp(rsi, Operand(rbp, StandardFrameConstants::kContextOffset));
+    // Reset the context register.
+    if (!reg.is(rsi)) {
+      __ Set(rsi, 0);
+    }
     __ CallRuntimeSaveDoubles(Runtime::kAllocateHeapNumber);
     RecordSafepointWithRegisters(
         instr->pointer_map(), 0, Safepoint::kNoLazyDeopt);
     __ StoreToSafepointRegisterSlot(reg, rax);
   }
 
   // Done. Put the value in temp_xmm into the value of the allocated heap
   // number.
   __ bind(&done);
   __ Movsd(FieldOperand(reg, HeapNumber::kValueOffset), temp_xmm);
@@ skipping 29 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, Smi::FromInt(0));
 
   {
     PushSafepointRegistersScope scope(this);
-    // NumberTagD uses 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.
-    __ movp(rsi, Operand(rbp, StandardFrameConstants::kContextOffset));
+    // Reset the context register.
+    if (!reg.is(rsi)) {
+      __ Move(rsi, 0);
+    }
     __ CallRuntimeSaveDoubles(Runtime::kAllocateHeapNumber);
     RecordSafepointWithRegisters(
         instr->pointer_map(), 0, Safepoint::kNoLazyDeopt);
     __ movp(kScratchRegister, rax);
   }
   __ movp(reg, kScratchRegister);
 }
 
 
 void LCodeGen::DoSmiTag(LSmiTag* instr) {
@@ skipping 943 matching lines @@
   __ bind(deferred->exit());
   __ bind(&done);
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64