Fix a missing peephole optimization in ia32 code exposed with Kevin's...

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 702 matching lines @@
 
 void Assembler::add(Register dst, const Operand& src) {
   EnsureSpace ensure_space(this);
   last_pc_ = pc_;
   EMIT(0x03);
   emit_operand(dst, src);
 }
 
 
 void Assembler::add(const Operand& dst, const Immediate& x) {
+  ASSERT(reloc_info_writer.last_pc() != NULL);
+  if (FLAG_push_pop_elimination && (reloc_info_writer.last_pc() <= last_pc_)) {
+    byte instr = last_pc_[0];
+    if ((instr & 0xf8) == 0x50) {
+      // Last instruction was a push. Check whether this is a pop without a
+      // result.
+      if ((dst.is_reg(esp)) &&
+          (x.x_ == kPointerSize) && (x.rmode_ == RelocInfo::NONE)) {
+        pc_ = last_pc_;
+        last_pc_ = NULL;
+        if (FLAG_print_push_pop_elimination) {
+          PrintF("%d push/pop(noreg) eliminated\n", pc_offset());
+        }
+        return;
+      }
+    }
+  }
   EnsureSpace ensure_space(this);
   last_pc_ = pc_;
   emit_arith(0, dst, x);
 }
 
 
 void Assembler::and_(Register dst, int32_t imm32) {
   EnsureSpace ensure_space(this);
   last_pc_ = pc_;
   emit_arith(4, Operand(dst), Immediate(imm32));
@@ skipping 1297 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