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

src/crankshaft/arm64/lithium-codegen-arm64.cc

Index: src/crankshaft/arm64/lithium-codegen-arm64.cc
diff --git a/src/crankshaft/arm64/lithium-codegen-arm64.cc b/src/crankshaft/arm64/lithium-codegen-arm64.cc
index 9fe4f5231a2b3a9cbb4f4e576f1481c2734bf35d..ece3689a4f7b2e3bf8f9b553fbe51d7ea905d708 100644
--- a/src/crankshaft/arm64/lithium-codegen-arm64.cc
+++ b/src/crankshaft/arm64/lithium-codegen-arm64.cc
@@ -4195,12 +4195,10 @@ void LCodeGen::DoDeferredNumberTagD(LNumberTagD* instr) {
   __ 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);
@@ -4260,13 +4258,10 @@ void LCodeGen::DoDeferredNumberTagU(LInstruction* instr,
   {
     // 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);