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AMDGPU: Make findUsedSGPR more readable 

Add more comments etc.

llvm-svn: 251996
This commit is contained in:
Matt Arsenault 2015-11-03 22:30:15 +00:00
parent 782c03bb7e
commit 6c0674112a
1 changed files with 18 additions and 7 deletions
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25
llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
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@ -2665,6 +2665,7 @@ const TargetRegisterClass *SIInstrInfo::getDestEquivalentVGPRClass(
}
}
// Find the one SGPR operand we are allowed to use.
unsigned SIInstrInfo::findUsedSGPR(const MachineInstr *MI,
int OpIndices[3]) const {
const MCInstrDesc &Desc = MI->getDesc();
@ -2691,16 +2692,23 @@ unsigned SIInstrInfo::findUsedSGPR(const MachineInstr *MI,
break;
const MachineOperand &MO = MI->getOperand(Idx);
if (RI.isSGPRClassID(Desc.OpInfo[Idx].RegClass))
SGPRReg = MO.getReg();
if (!MO.isReg())
continue;
if (MO.isReg() && RI.isSGPRClass(MRI.getRegClass(MO.getReg())))
UsedSGPRs[i] = MO.getReg();
// Is this operand statically required to be an SGPR based on the operand
// constraints?
const TargetRegisterClass *OpRC = RI.getRegClass(Desc.OpInfo[Idx].RegClass);
bool IsRequiredSGPR = RI.isSGPRClass(OpRC);
if (IsRequiredSGPR)
return MO.getReg();
// If this could be a VGPR or an SGPR, Check the dynamic register class.
unsigned Reg = MO.getReg();
const TargetRegisterClass *RegRC = MRI.getRegClass(Reg);
if (RI.isSGPRClass(RegRC))
UsedSGPRs[i] = Reg;
}
if (SGPRReg != AMDGPU::NoRegister)
return SGPRReg;
// We don't have a required SGPR operand, so we have a bit more freedom in
// selecting operands to move.
@ -2711,6 +2719,9 @@ unsigned SIInstrInfo::findUsedSGPR(const MachineInstr *MI,
// V_FMA_F32 v0, s0, s0, s0 -> No moves
// V_FMA_F32 v0, s0, s1, s0 -> Move s1
// TODO: If some of the operands are 64-bit SGPRs and some 32, we should
// prefer those.
if (UsedSGPRs[0] != AMDGPU::NoRegister) {
if (UsedSGPRs[0] == UsedSGPRs[1] || UsedSGPRs[0] == UsedSGPRs[2])
SGPRReg = UsedSGPRs[0];