[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 1194142be051c8767dffbea3872470a6776ae1da..024e724a7062a4070e1eefbe04785691d6e0a259 100644
--- a/src/crankshaft/ia32/lithium-codegen-ia32.cc
+++ b/src/crankshaft/ia32/lithium-codegen-ia32.cc
@@ -4264,13 +4264,10 @@ 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);
@@ -4320,12 +4317,10 @@ 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);
@@ -4414,7 +4409,7 @@ void LCodeGen::EmitNumberUntagD(LNumberUntagD* instr, Register input_reg,
   }
 
   __ bind(&load_smi);
-  // Smi to XMM conversion. Clobbering a temp is faster than re-tagging the
+  // Smi to XMM conversion. Clobbering a temp is faster than -tagging the

[Jakob Kummerow, 2016/07/13 15:56:56]

accidental edit?

   // input register since we avoid dependencies.
   __ mov(temp_reg, input_reg);
   __ SmiUntag(temp_reg);  // Untag smi before converting to float.