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[AArch64] Refactor cheap cost model

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Refactor the order in `TII::isAsCheapAsAMove()` to ease future development
and maintenance.  Practically NFC.

llvm-svn: 343489
This commit is contained in:
Evandro Menezes 2018-10-01 16:11:19 +00:00
parent 92a71efe9a
commit a59148b265
1 changed files with 23 additions and 12 deletions
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35
lib/Target/AArch64/AArch64InstrInfo.cpp
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@ -675,6 +675,26 @@ bool AArch64InstrInfo::isAsCheapAsAMove(const MachineInstr &MI) const {
if (!Subtarget.hasCustomCheapAsMoveHandling())
return MI.isAsCheapAsAMove();
const unsigned Opcode = MI.getOpcode();
// Firstly, check cases gated by features.
if (Subtarget.hasZeroCycleZeroingFP()) {
if (Opcode == AArch64::FMOVH0 ||
Opcode == AArch64::FMOVS0 ||
Opcode == AArch64::FMOVD0)
return true;
}
if (Subtarget.hasZeroCycleZeroingGP()) {
if (Opcode == TargetOpcode::COPY &&
(MI.getOperand(1).getReg() == AArch64::WZR ||
MI.getOperand(1).getReg() == AArch64::XZR))
return true;
}
// Secondly, check cases specific to sub-targets.
if (Subtarget.hasExynosCheapAsMoveHandling()) {
if (isExynosResetFast(MI) || isExynosShiftLeftFast(MI))
return true;
@ -682,7 +702,9 @@ bool AArch64InstrInfo::isAsCheapAsAMove(const MachineInstr &MI) const {
return MI.isAsCheapAsAMove();
}
switch (MI.getOpcode()) {
// Finally, check generic cases.
switch (Opcode) {
default:
return false;
@ -723,17 +745,6 @@ bool AArch64InstrInfo::isAsCheapAsAMove(const MachineInstr &MI) const {
return canBeExpandedToORR(MI, 32);
case AArch64::MOVi64imm:
return canBeExpandedToORR(MI, 64);
// It is cheap to zero out registers if the subtarget has ZeroCycleZeroing
// feature.
case AArch64::FMOVH0:
case AArch64::FMOVS0:
case AArch64::FMOVD0:
return Subtarget.hasZeroCycleZeroingFP();
case TargetOpcode::COPY:
return (Subtarget.hasZeroCycleZeroingGP() &&
(MI.getOperand(1).getReg() == AArch64::WZR ||
MI.getOperand(1).getReg() == AArch64::XZR));
}
llvm_unreachable("Unknown opcode to check as cheap as a move!");