Author: [EMAIL PROTECTED]
Date: Tue Sep 23 06:31:14 2008
New Revision: 366
Modified:
branches/bleeding_edge/src/assembler-ia32.cc
Log:
Added some peephole optimizaitions regarding push of immediate followed
by pop eax.
Review URL: http://codereview.chromium.org/4212
Modified: branches/bleeding_edge/src/assembler-ia32.cc
==============================================================================
--- branches/bleeding_edge/src/assembler-ia32.cc (original)
+++ branches/bleeding_edge/src/assembler-ia32.cc Tue Sep 23 06:31:14 2008
@@ -469,7 +469,48 @@
}
return;
}
+ } else if (instr == 0x6a && dst.is(eax)) { // push of immediate 8 bit
+ byte imm8 = last_pc_[1];
+ if (imm8 == 0) {
+ // 6a00 push 0x0
+ // 58 pop eax
+ last_pc_[0] = 0x31;
+ last_pc_[1] = 0xc0;
+ // change to
+ // 31c0 xor eax,eax
+ last_pc_ = NULL;
+ return;
+ } else {
+ // 6a00 push 0xXX
+ // 58 pop eax
+ last_pc_[0] = 0xb8;
+ EnsureSpace ensure_space(this);
+ if ((imm8 & 0x80) != 0) {
+ EMIT(0xff);
+ EMIT(0xff);
+ EMIT(0xff);
+ // change to
+ // b8XXffffff mov eax,0xffffffXX
+ } else {
+ EMIT(0x00);
+ EMIT(0x00);
+ EMIT(0x00);
+ // change to
+ // b8XX000000 mov eax,0x000000XX
+ }
+ last_pc_ = NULL;
+ return;
+ }
+ } else if (instr == 0x68 && dst.is(eax)) { // push of immediate 32 bit
+ // 68XXXXXXXX push 0xXXXXXXXX
+ // 58 pop eax
+ last_pc_[0] = 0xb8;
+ last_pc_ = NULL;
+ // change to
+ // b8XXXXXXXX mov eax,0xXXXXXXXX
+ return;
}
+
// Other potential patterns for peephole:
// 0x712716 102 890424 mov [esp], eax
// 0x712719 105 8b1424 mov edx, [esp]
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