Change the register allocator so that it no longer tracks references...

src/ia32/register-allocator-ia32-inl.h

+// Copyright 2009 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
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+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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+
+#ifndef V8_IA32_REGISTER_ALLOCATOR_IA32_INL_H_
+#define V8_IA32_REGISTER_ALLOCATOR_IA32_INL_H_
+
+#include "v8.h"
+
+namespace v8 {
+namespace internal {
+
+// -------------------------------------------------------------------------
+// RegisterAllocator implementation.
+
+bool RegisterAllocator::IsReserved(Register reg) {
+  // The code for this test relies on the order of register codes.
+  return reg.code() >= esp.code() && reg.code() <= esi.code();
+}
+
+
+// The register allocator uses small integers to represent the
+// non-reserved assembler registers.  The mapping is:
+
+// eax <-> 0, ebx <-> 1, ecx <-> 2, edx <-> 3, edi <-> 4.
+
+int RegisterAllocator::ToNumber(Register reg) {
+  ASSERT(reg.is_valid() && !IsReserved(reg));
+  static int numbers[] = {
+    0,   // eax
+    2,   // ecx
+    3,   // edx
+    1,   // ebx
+    -1,  // esp
+    -1,  // ebp
+    -1,  // esi
+    4    // edi
+  };
+  return numbers[reg.code()];
+}

[William Hesse, 2009/05/26 13:33:32]

You could map the codes 0,1,2,3, and 7 to the range 0..4 by
(i + 1) & 7, and back by (i+7) & 7.  Would this be faster than the lookup
tables?

[Kevin Millikin (Chromium), 2009/05/27 07:43:07]

I'll give it a try.  It has the side effect of allocating in a different order
(changing our bias toward eax into a bias toward edi).

+
+
+Register RegisterAllocator::ToRegister(int num) {
+  ASSERT(num >= 0 && num < kNumRegisters);
+  static Register registers[] = { eax, ebx, ecx, edx, edi };
+  return registers[num];
+}
+
+
+void RegisterAllocator::Initialize() {
+  Reset();
+  // The non-reserved edi register is live on JS function entry.
+  Use(edi);  // JS function.
+}
+
+
+} }  // namespace v8::internal
+
+#endif  // V8_IA32_REGISTER_ALLOCATOR_IA32_INL_H_