MIPS: To fully support hydrogen code stubs which accept a variable number of...

MIPS: To fully support hydrogen code stubs which accept a variable number of arguments, the HReturn/LReturn instruction needs to be able to determine argument count from a stack evaluation rather than as a constant from scope.

Port r13888 (33905114)

BUG=

Review URL: https://codereview.chromium.org/12414011

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13910 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/lithium-codegen-mips.cc

@@ -2558,11 +2558,20 @@ void LCodeGen::DoReturn(LReturn* instr) {
     }
   }
   if (NeedsEagerFrame()) {
-    int32_t sp_delta = (GetParameterCount() + 1) * kPointerSize;
     __ mov(sp, fp);
     __ Pop(ra, fp);
-    if (!info()->IsStub()) {
-      __ Addu(sp, sp, Operand(sp_delta));
+
+    if (instr->has_constant_parameter_count()) {
+      int parameter_count = ToInteger32(instr->constant_parameter_count());
+      int32_t sp_delta = (parameter_count + 1) * kPointerSize;
+      if (sp_delta != 0) {
+        __ Addu(sp, sp, Operand(sp_delta));
+      }
+    } else {
+      Register reg = ToRegister(instr->parameter_count());
+      __ Addu(reg, reg, Operand(1));
+      __ sll(at, reg, kPointerSizeLog2);
+      __ Addu(sp, sp, at);
     }
   }
   __ Jump(ra);

src/mips/lithium-codegen-mips.h

@@ -201,7 +201,6 @@ class LCodeGen BASE_EMBEDDED {
                        Register temporary2);
 
   int GetStackSlotCount() const { return chunk()->spill_slot_count(); }
-  int GetParameterCount() const { return info()->num_parameters(); }
 
   void Abort(const char* reason);
   void Comment(const char* format, ...);

src/mips/lithium-mips.cc

@@ -1804,7 +1804,9 @@ LInstruction* LChunkBuilder::DoClampToUint8(HClampToUint8* instr) {
 
 
 LInstruction* LChunkBuilder::DoReturn(HReturn* instr) {
-  return new(zone()) LReturn(UseFixed(instr->value(), v0));
+  LOperand* parameter_count = UseRegisterOrConstant(instr->parameter_count());
+  return new(zone()) LReturn(UseFixed(instr->value(), v0),
+                             parameter_count);
 }
 
 

src/mips/lithium-mips.h

@@ -1343,14 +1343,24 @@ class LArithmeticT: public LTemplateInstruction<1, 2, 0> {
 };
 
 
-class LReturn: public LTemplateInstruction<0, 1, 0> {
+class LReturn: public LTemplateInstruction<0, 2, 0> {
  public:
-  explicit LReturn(LOperand* value) {
+  explicit LReturn(LOperand* value, LOperand* parameter_count) {
     inputs_[0] = value;
+    inputs_[1] = parameter_count;
   }
 
   LOperand* value() { return inputs_[0]; }
 
+  bool has_constant_parameter_count() {
+    return parameter_count()->IsConstantOperand();
+  }
+  LConstantOperand* constant_parameter_count() {
+    ASSERT(has_constant_parameter_count());
+    return LConstantOperand::cast(parameter_count());
+  }
+  LOperand* parameter_count() { return inputs_[1]; }
+
   DECLARE_CONCRETE_INSTRUCTION(Return, "return")
 };