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

src/crankshaft/ia32/lithium-codegen-ia32.cc

Index: src/crankshaft/ia32/lithium-codegen-ia32.cc
diff --git a/src/crankshaft/ia32/lithium-codegen-ia32.cc b/src/crankshaft/ia32/lithium-codegen-ia32.cc
index f1406df88d1a65b849ed13816078efc2485e5cc0..d389b4b88d3c4fca23f83141168d526850c8480e 100644
--- a/src/crankshaft/ia32/lithium-codegen-ia32.cc
+++ b/src/crankshaft/ia32/lithium-codegen-ia32.cc
@@ -4265,13 +4265,10 @@ void LCodeGen::DoDeferredNumberTagIU(LInstruction* instr,
 
     // 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);
@@ -4321,12 +4318,10 @@ void LCodeGen::DoDeferredNumberTagD(LNumberTagD* instr) {
   __ 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);