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x64Emitter: short MOV for 64bit immediates (2) 

Prior to this commit, the emitter would unconditionally emit a 10-byte
instruction known as MOVABS when loading a 64-bit immediate to a
register.

0:  48 b8 ef be ad de 00    movabs rax,0xdeadbeef
7:  00 00 00

With this change, it will instead rely on the fact that on x64 writes to
32-bit registers are automatically zero extended to 64-bits, allowing
us to emit a 5 or 6-bytes instruction with the same effect for certain
immediates.

0:  b8 ef be ad de          mov    eax,0xdeadbeef
This commit is contained in:
Sintendo 2018-09-14 21:57:00 +02:00
parent 575f1b309a
commit 53a947749a
1 changed files with 6 additions and 0 deletions
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6
Source/Core/Common/x64Emitter.cpp
View File

@ -1591,6 +1591,12 @@ void XEmitter::XOR(int bits, const OpArg& a1, const OpArg& a2)
}
void XEmitter::MOV(int bits, const OpArg& a1, const OpArg& a2)
{
if (bits == 64 && a1.IsSimpleReg() && a2.scale == SCALE_IMM64 &&
a2.offset == static_cast<u32>(a2.offset))
{
WriteNormalOp(32, NormalOp::MOV, a1, a2.AsImm32());
return;
}
if (a1.IsSimpleReg() && a2.IsSimpleReg() && a1.GetSimpleReg() == a2.GetSimpleReg())
ERROR_LOG(DYNA_REC, "Redundant MOV @ %p - bug in JIT?", code);
WriteNormalOp(bits, NormalOp::MOV, a1, a2);