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x64Emitter: optimize immediate sizes 

A nice alternative than trying to do it throughout the JIT.
This commit is contained in:
Fiora 2014-08-06 16:36:53 -04:00
parent e1701951b2
commit 75b3e425fd
1 changed files with 18 additions and 3 deletions
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21
Source/Core/Common/x64Emitter.cpp
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@ -18,6 +18,7 @@ struct NormalOpDef
u8 toRm8, toRm32, fromRm8, fromRm32, imm8, imm32, simm8, ext;
};
// 0xCC is code for invalid combination of immediates
static const NormalOpDef nops[11] =
{
{0x00, 0x01, 0x02, 0x03, 0x80, 0x81, 0x83, 0}, //ADD
@ -1057,8 +1058,20 @@ void OpArg::WriteNormalOp(XEmitter *emit, bool toRM, NormalOp op, const OpArg &o
(operand.scale == SCALE_IMM32 && bits == 32) ||
(operand.scale == SCALE_IMM32 && bits == 64))
{
emit->Write8(nops[op].imm32);
immToWrite = bits == 16 ? 16 : 32;
// Try to save immediate size if we can, but first check to see
// if the instruction supports simm8.
if (nops[op].simm8 != 0xCC &&
((operand.scale == SCALE_IMM16 && (s16)operand.offset == (s8)operand.offset) ||
(operand.scale == SCALE_IMM32 && (s32)operand.offset == (s8)operand.offset)))
{
emit->Write8(nops[op].simm8);
immToWrite = 8;
}
else
{
emit->Write8(nops[op].imm32);
immToWrite = bits == 16 ? 16 : 32;
}
}
else if ((operand.scale == SCALE_IMM8 && bits == 16) ||
(operand.scale == SCALE_IMM8 && bits == 32) ||
@ -1182,7 +1195,9 @@ void XEmitter::IMUL(int bits, X64Reg regOp, OpArg a1, OpArg a2)
Write8(0x66);
a1.WriteRex(this, bits, bits, regOp);
if (a2.GetImmBits() == 8) {
if (a2.GetImmBits() == 8 ||
(a2.GetImmBits() == 16 && (s8)a2.offset == (s16)a2.offset) ||
(a2.GetImmBits() == 32 && (s8)a2.offset == (s32)a2.offset)) {
Write8(0x6B);
a1.WriteRest(this, 1, regOp);
Write8((u8)a2.offset);