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Use movaps / movapd (instead of movss / movsd) to do FR32 / FR64 reg to reg

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transfer.

According to the Intel P4 Optimization Manual:

Moves that write a portion of a register can introduce unwanted
dependences. The movsd reg, reg instruction writes only the bottom
64 bits of a register, not to all 128 bits. This introduces a dependence on
the preceding instruction that produces the upper 64 bits (even if those
bits are not longer wanted). The dependence inhibits register renaming,
and thereby reduces parallelism.

Not to mention movaps is shorter than movss.

llvm-svn: 26226
This commit is contained in:
Evan Cheng 2006-02-16 01:50:02 +00:00
parent 57142c7e12
commit 74228303ad
1 changed files with 2 additions and 2 deletions
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4
lib/Target/X86/X86RegisterInfo.cpp
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@ -106,9 +106,9 @@ void X86RegisterInfo::copyRegToReg(MachineBasicBlock &MBB,
} else if (RC == &X86::RFPRegClass || RC == &X86::RSTRegClass) {
Opc = X86::FpMOV;
} else if (RC == &X86::FR32RegClass || RC == &X86::V4F4RegClass) {
Opc = X86::MOVSSrr;
Opc = X86::MOVAPSrr;
} else if (RC == &X86::FR64RegClass || RC == &X86::V2F8RegClass) {
Opc = X86::MOVSDrr;
Opc = X86::MOVAPDrr;
} else {
assert(0 && "Unknown regclass");
abort();