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

src/crankshaft/arm64/lithium-codegen-arm64.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.
 
 #include "src/crankshaft/arm64/lithium-codegen-arm64.h"
 
 #include "src/arm64/frames-arm64.h"
 #include "src/base/bits.h"
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
@@ skipping 4177 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 result = ToRegister(instr->result());
   __ Mov(result, 0);
 
   PushSafepointRegistersScope scope(this);
-  // NumberTagU 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));
+  // Reset the context register.
+  if (!result.is(cp)) {
+    __ Mov(cp, 0);
+  }
   __ CallRuntimeSaveDoubles(Runtime::kAllocateHeapNumber);
   RecordSafepointWithRegisters(
       instr->pointer_map(), 0, Safepoint::kNoLazyDeopt);
   __ StoreToSafepointRegisterSlot(x0, result);
 }
 
 
 void LCodeGen::DoNumberTagD(LNumberTagD* instr) {
   class DeferredNumberTagD: public LDeferredCode {
    public:
@@ skipping 39 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.
   __ Mov(dst, 0);
   {
     // Preserve the value of all registers.
     PushSafepointRegistersScope scope(this);
-
-    // NumberTagU 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));
+    // Reset the context register.
+    if (!dst.is(cp)) {
+      __ Mov(cp, 0);
+    }
     __ CallRuntimeSaveDoubles(Runtime::kAllocateHeapNumber);
     RecordSafepointWithRegisters(
       instr->pointer_map(), 0, Safepoint::kNoLazyDeopt);
     __ StoreToSafepointRegisterSlot(x0, dst);
   }
 
   // Convert number to floating point and store in the newly allocated heap
   // number.
   __ Bind(&convert_and_store);
   DoubleRegister dbl_scratch = double_scratch();
@@ skipping 1437 matching lines @@
   // Index is equal to negated out of object property index plus 1.
   __ Sub(result, result, Operand::UntagSmiAndScale(index, kPointerSizeLog2));
   __ Ldr(result, FieldMemOperand(result,
                                  FixedArray::kHeaderSize - kPointerSize));
   __ Bind(deferred->exit());
   __ Bind(&done);
 }
 
 }  // namespace internal
 }  // namespace v8