[turbofan] Avoid allocating rest parameters for spread calls.

src/builtins/mips/builtins-mips.cc

Index: src/builtins/mips/builtins-mips.cc
diff --git a/src/builtins/mips/builtins-mips.cc b/src/builtins/mips/builtins-mips.cc
index 6f9cd9a3ff66c9ddb7ea84d37882984ed2e9bcec..24fe271cb346d02bb131e52d391a5456c5ed8c75 100644
--- a/src/builtins/mips/builtins-mips.cc
+++ b/src/builtins/mips/builtins-mips.cc
@@ -2168,68 +2168,64 @@ void Builtins::Generate_Apply(MacroAssembler* masm) {
 }
 
 // static
-void Builtins::Generate_CallForwardVarargs(MacroAssembler* masm,
-                                           Handle<Code> code) {
+void Builtins::Generate_ForwardVarargs(MacroAssembler* masm,
+                                       Handle<Code> code) {
   // ----------- S t a t e -------------
-  //  -- a1    : the target to call (can be any Object)
-  //  -- a2    : start index (to support rest parameters)
-  //  -- ra    : return address.
-  //  -- sp[0] : thisArgument
+  //  -- a0 : the number of arguments (not including the receiver)
+  //  -- a3 : the new.target (for [[Construct]] calls)
+  //  -- a1 : the target to call (can be any Object)
+  //  -- a2 : start index (to support rest parameters)
   // -----------------------------------
 
   // Check if we have an arguments adaptor frame below the function frame.
   Label arguments_adaptor, arguments_done;
-  __ lw(a3, MemOperand(fp, StandardFrameConstants::kCallerFPOffset));
-  __ lw(a0, MemOperand(a3, CommonFrameConstants::kContextOrFrameTypeOffset));
-  __ Branch(&arguments_adaptor, eq, a0,
+  __ lw(t3, MemOperand(fp, StandardFrameConstants::kCallerFPOffset));
+  __ lw(t2, MemOperand(t3, CommonFrameConstants::kContextOrFrameTypeOffset));
+  __ Branch(&arguments_adaptor, eq, t2,
             Operand(StackFrame::TypeToMarker(StackFrame::ARGUMENTS_ADAPTOR)));
   {
-    __ lw(a0, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
-    __ lw(a0, FieldMemOperand(a0, JSFunction::kSharedFunctionInfoOffset));
-    __ lw(a0,
-          FieldMemOperand(a0, SharedFunctionInfo::kFormalParameterCountOffset));
-    __ mov(a3, fp);
+    __ lw(t2, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
+    __ lw(t2, FieldMemOperand(t2, JSFunction::kSharedFunctionInfoOffset));
+    __ lw(t2,
+          FieldMemOperand(t2, SharedFunctionInfo::kFormalParameterCountOffset));
+    __ mov(t3, fp);
   }
   __ Branch(&arguments_done);
   __ bind(&arguments_adaptor);
   {
     // Just get the length from the ArgumentsAdaptorFrame.
-    __ lw(a0, MemOperand(a3, ArgumentsAdaptorFrameConstants::kLengthOffset));
+    __ lw(t2, MemOperand(t3, ArgumentsAdaptorFrameConstants::kLengthOffset));
   }
   __ bind(&arguments_done);
 
-  Label stack_empty, stack_done, stack_overflow;
-  __ SmiUntag(a0);
-  __ Subu(a0, a0, a2);
-  __ Branch(&stack_empty, le, a0, Operand(zero_reg));
+  Label stack_done, stack_overflow;
+  __ SmiUntag(t2);
+  __ Subu(t2, t2, a2);
+  __ Branch(&stack_done, le, t2, Operand(zero_reg));
   {
     // Check for stack overflow.
-    Generate_StackOverflowCheck(masm, a0, t0, t1, &stack_overflow);
+    Generate_StackOverflowCheck(masm, t2, t0, t1, &stack_overflow);
 
     // Forward the arguments from the caller frame.
     {
       Label loop;
-      __ mov(a2, a0);
+      __ Addu(a0, a0, t2);
       __ bind(&loop);
       {
-        __ Lsa(at, a3, a2, kPointerSizeLog2);
+        __ Lsa(at, t3, t2, kPointerSizeLog2);
         __ lw(at, MemOperand(at, 1 * kPointerSize));
         __ push(at);
-        __ Subu(a2, a2, Operand(1));
-        __ Branch(&loop, ne, a2, Operand(zero_reg));
+        __ Subu(t2, t2, Operand(1));
+        __ Branch(&loop, ne, t2, Operand(zero_reg));
       }
     }
   }
   __ Branch(&stack_done);
   __ bind(&stack_overflow);
   __ TailCallRuntime(Runtime::kThrowStackOverflow);
-  __ bind(&stack_empty);
-  {
-    // We just pass the receiver, which is already on the stack.
-    __ li(a0, Operand(0));
-  }
   __ bind(&stack_done);
 
+  // Tail-call to the {code} handler.
   __ Jump(code, RelocInfo::CODE_TARGET);
 }