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Promote VMOVS to VMOVD when possible. 

On Cortex-A8, we use the NEON v2f32 instructions for f32 arithmetic. For
better latency, we also send D-register copies down the NEON pipeline by
translating them to vorr instructions.

This patch promotes even S-register copies to D-register copies when
possible so they can also go down the NEON pipeline.  Example:

        vldr.32 s0, LCPI0_0
    loop:
        vorr    d1, d0, d0
    loop2:
        ...
        vadd.f32        d1, d1, d16

The vorr instruction looked like this after regalloc:

    %S2<def> = COPY %S0, %D1<imp-def>

Copies involving odd S-registers, and copies that don't define the full
D-register are left alone.

llvm-svn: 137182
This commit is contained in:
Jakob Stoklund Olesen 2011-08-09 23:41:44 +00:00
parent 92b942b1b5
commit 6a14dc01ff
1 changed files with 29 additions and 2 deletions
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31
llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp
View File

@ -629,9 +629,36 @@ void ARMBaseInstrInfo::copyPhysReg(MachineBasicBlock &MBB,
bool SPRSrc = ARM::SPRRegClass.contains(SrcReg);
unsigned Opc;
if (SPRDest && SPRSrc)
if (SPRDest && SPRSrc) {
Opc = ARM::VMOVS;
else if (GPRDest && SPRSrc)
// An even S-S copy may be feeding a NEON v2f32 instruction being used for
// f32 operations. In that case, it is better to copy the full D-regs with
// a VMOVD since that can be converted to a NEON-domain move by
// NEONMoveFix.cpp. Check that MI is the original COPY instruction, and
// that it really defines the whole D-register.
if ((DestReg - ARM::S0) % 2 == 0 && (SrcReg - ARM::S0) % 2 == 0 &&
I != MBB.end() && I->isCopy() &&
I->getOperand(0).getReg() == DestReg &&
I->getOperand(1).getReg() == SrcReg) {
// I is pointing to the ortiginal COPY instruction.
// Find the parent D-registers.
const TargetRegisterInfo *TRI = &getRegisterInfo();
unsigned SrcD = TRI->getMatchingSuperReg(SrcReg, ARM::ssub_0,
&ARM::DPRRegClass);
unsigned DestD = TRI->getMatchingSuperReg(DestReg, ARM::ssub_0,
&ARM::DPRRegClass);
// Be careful to not clobber an INSERT_SUBREG that reads and redefines a
// D-register. There must be an <imp-def> of destD, and no <imp-use>.
if (I->definesRegister(DestD, TRI) && !I->readsRegister(DestD, TRI)) {
Opc = ARM::VMOVD;
SrcReg = SrcD;
DestReg = DestD;
if (KillSrc)
KillSrc = I->killsRegister(SrcReg, TRI);
}
}
} else if (GPRDest && SPRSrc)
Opc = ARM::VMOVRS;
else if (SPRDest && GPRSrc)
Opc = ARM::VMOVSR;