Use unspilled virtual frames when compiling compare operations....

src/assembler-ia32.cc

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions
 // are met:
 //
 // - Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 //
@@ skipping 725 matching lines @@
   ASSERT(CpuFeatures::IsEnabled(CpuFeatures::CMOV));
   EnsureSpace ensure_space(this);
   last_pc_ = pc_;
   UNIMPLEMENTED();
   USE(cc);
   USE(dst);
   USE(src);
 }
 
 
+void Assembler::xchg(Register dst, Register src) {
+  EnsureSpace ensure_space(this);
+  last_pc_ = pc_;
+  if (src.is(eax) || dst.is(eax)) {  // Single-byte encoding
+    if (dst.is(eax)) {
+      dst = src;  // No need to copy eax to src, we assume src is eax.

[Kevin Millikin (Chromium), 2008/12/29 09:05:38]

More straightforward:
EMIT(0x90 | (dst.is(eax) ? src.code() : dst.code()));

[William Hesse, 2008/12/29 11:47:42]

Done.

+    }
+    EMIT(0x90 | dst.code());
+  } else {
+    EMIT(0x87);
+    EMIT(0xC0 | src.code() << 3 | dst.code());
+  }
+}
+
+
 void Assembler::adc(Register dst, int32_t imm32) {
   EnsureSpace ensure_space(this);
   last_pc_ = pc_;
   emit_arith(2, Operand(dst), Immediate(imm32));
 }
 
 
 void Assembler::adc(Register dst, const Operand& src) {
   EnsureSpace ensure_space(this);
   last_pc_ = pc_;
@@ skipping 1384 matching lines @@
   ASSERT(bound_label.is_bound());
   ASSERT(0 <= position);
   ASSERT(position + static_cast<int>(sizeof(uint32_t)) <= pc_offset());
   ASSERT(long_at(position) == 0);  // only initialize once!
 
   uint32_t label_loc = reinterpret_cast<uint32_t>(addr_at(bound_label.pos()));
   long_at_put(position, label_loc);
 }
 
 } }  // namespace v8::internal