Introduce StackArgumentsAccessor class for X64

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
diff --git a/src/x64/macro-assembler-x64.h b/src/x64/macro-assembler-x64.h
index e611c8ae27999a9520d0aa07bfa050b51a0bb831..d2b066e4b1e3d0ae4de38c62ad79a77a346d06c1 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -1479,6 +1479,60 @@ class CodePatcher {
 };
 
 
+class StackArguments BASE_EMBEDDED {

[danno, 2013/08/05 15:17:56]

I would call this StackArgumentsAccessor

[haitao.feng, 2013/08/06 11:49:55]

Done.

+ public:
+  // argc could be an immediate or in a register.
+  // extra is 1 when the receiver is considered as argument[0].
+  // disp is the displacement between rsp and return address.
+  StackArguments(int immediate, int extra = 0, int disp = 0)
+      : reg_(no_reg), immediate_(immediate), extra_(extra), disp_(disp) { }
+
+  StackArguments(Register reg, int extra = 0, int disp = 0)

[danno, 2013/08/05 15:17:56]

I find all the math with extra and disp a bit confusing. How about adding an
enum for the receiver mode:

StackArgumentsAccessorReceiverMode {
  ARGUMENTS_CONTAIN_RECEIVER,
  ARGUMENTS_DONT_CONTAIN_RECEIVER
};

The default should be ARGUMENTS_CONTAIN_RECEIVER since you more often than not
pass 1 for extra currently. You can then turn this into receiver_size_ that is
used in the math calculations below.

Also, call disp and disp_ dispacement_to_sp and dispacement_to_sp_,
respectively, this make the comment superfluous.

[haitao.feng, 2013/08/06 11:49:55]

Done.

+      : reg_(reg), immediate_(0), extra_(extra), disp_(disp) { }
+
+  StackArguments(const ParameterCount& parameter_count,
+                 int extra = 0,
+                 int disp = 0)
+      : reg_(parameter_count.is_reg() ? parameter_count.reg() : no_reg),
+        immediate_(parameter_count.is_immediate() ?
+                   parameter_count.immediate() : 0),
+        extra_(extra),
+        disp_(disp) { }
+
+  Operand operator[] (int index) {

[danno, 2013/08/05 15:17:56]

I think it's better to not overide the [] operator, since StackArgumentsAccessor
isn't a container per se. I think it would be better to call this 

GetArgumentOperand(int index) { ... } 

[haitao.feng, 2013/08/06 11:49:55]

Done.

+    if (index >= 0) {
+      if (reg_.is(no_reg)) {
+        // argument[0] is at rsp + disp + kPCOnSackSize +
+        // (immediate_ + extra_ - 1) * kPointerSize.
+        ASSERT(immediate_ + extra_ > 0);
+        return Operand(rsp, disp_ + kPCOnStackSize +
+                       (immediate_ + extra_ - 1 - index) * kPointerSize);
+      } else {
+        // argument[0] is at rsp + disp + kPCOnSackSize +
+        // reg_ * times_pointer_size + (extra_ - 1) * kPointerSize.
+        return Operand(rsp, reg_, times_pointer_size, disp_ + kPCOnStackSize +
+                       (extra_ - 1 - index) * kPointerSize);
+      }
+    } else {

[danno, 2013/08/05 15:17:56]

I think the handling of negative arguments is pretty confusing. Do you really
need to support them?

[haitao.feng, 2013/08/06 11:49:55]

Done.

+      // Reverse order, argument[-1] is at rsp + disp + kPCOnSackSize.
+      ASSERT(reg_.is(no_reg) || (-index <= immediate_));
+      return Operand(rsp, disp_ + kPCOnStackSize + (-index - 1) * kPointerSize);
+    }
+  }
+
+  Operand GetReceiver() {

[danno, 2013/08/05 15:17:56]

... and this GetReceiverOperand()

[haitao.feng, 2013/08/06 11:49:55]

Done.

+    ASSERT(extra_ == 1);
+    return (*this)[0];
+  }
+
+ private:
+  const Register reg_;
+  const int immediate_;
+  const int extra_;
+  const int disp_;
+};
+
+
 // -----------------------------------------------------------------------------
 // Static helper functions.
 
@@ -1523,6 +1577,41 @@ inline Operand StackOperandForReturnAddress(int32_t disp) {
 }
 
 
+// Computes the argument address from the argument 0 (might be receiver)

[danno, 2013/08/05 15:17:56]

Do you need any of these here and below any more?

[haitao.feng, 2013/08/06 11:49:55]

Done. Sorry, I remembered I removed all of them. Maybe I did not commit it.

+// at rsp + disp + kPCOnStackSize + (total - 1) * kPointerSize, disp is the
+// displacement between the rsp and the return address.
+inline Operand StackOperandForArgument(int index, int total, int disp = 0) {
+  return Operand(rsp, disp + kPCOnStackSize +
+                 (total - 1 - index) * kPointerSize);
+}
+
+
+// Computes the argument address in reverse order, i.e., from the last argument
+// at rsp + disp + kPCOnStackSize, disp is the displacement between the rsp
+// and the return address.
+inline Operand StackOperandForReversedArgument(int index, int disp = 0) {
+  return Operand(rsp, disp + kPCOnStackSize + index * kPointerSize);
+}
+
+
+inline Operand StackOperandForReversedArgument(Register index,
+                                               int offset,
+                                               int disp = 0) {
+  return Operand(rsp, index, times_pointer_size,
+                 disp + kPCOnStackSize + offset * kPointerSize);
+}
+
+
+inline Operand StackOperandForReceiver(int index, int disp = 0) {
+  return StackOperandForReversedArgument(index, disp);
+}
+
+
+inline Operand StackOperandForReceiver(Register index, int disp = 0) {
+  return StackOperandForReversedArgument(index, 0, disp);
+}
+
+
 #ifdef GENERATED_CODE_COVERAGE
 extern void LogGeneratedCodeCoverage(const char* file_line);
 #define CODE_COVERAGE_STRINGIFY(x) #x