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[PowerPC] Always use mfocrf if available

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When accessing just a single CR register, it is always preferable to
use mfocrf instead of mfcr, if the former is available on the CPU.

Current code makes that distinction in many, but not all places
where a single CR register value is retrieved.  One missing
location is PPCRegisterInfo::lowerCRSpilling.

To fix this and make this simpler in the future, this patch changes
the bulk of the back-end to always assume mfocrf is available and
simply generate it when needed.

On machines that actually do not support mfocrf, the instruction
is replaced by mfcr at the very end, in EmitInstruction.

This has the additional benefit that we no longer need the
MFCRpseud hack, since before EmitInstruction we always have
a MFOCRF instruction pattern, which already models data flow
as required.

The patch also adds the MFOCRF8 version of the instruction,
which was missing so far.

Except for the PPCRegisterInfo::lowerCRSpilling case, no change
in generated code intended.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185556 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Ulrich Weigand
2013-07-03 17:05:42 +00:00
parent 73477b9f32
commit 965b20e39c
9 changed files with 42 additions and 65 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
lib/Target/PowerPC/MCTargetDesc/PPCMCCodeEmitter.cpp
View File

@@ -228,9 +228,8 @@ unsigned PPCMCCodeEmitter::
get_crbitm_encoding(const MCInst &MI, unsigned OpNo,
SmallVectorImpl<MCFixup> &Fixups) const {
const MCOperand &MO = MI.getOperand(OpNo);
assert((MI.getOpcode() == PPC::MTCRF ||
MI.getOpcode() == PPC::MFOCRF ||
MI.getOpcode() == PPC::MTCRF8) &&
assert((MI.getOpcode() == PPC::MTCRF || MI.getOpcode() == PPC::MTCRF8 ||
MI.getOpcode() == PPC::MFOCRF || MI.getOpcode() == PPC::MFOCRF8) &&
(MO.getReg() >= PPC::CR0 && MO.getReg() <= PPC::CR7));
return 0x80 >> CTX.getRegisterInfo()->getEncodingValue(MO.getReg());
}
@@ -242,7 +241,8 @@ getMachineOpValue(const MCInst &MI, const MCOperand &MO,
if (MO.isReg()) {
// MTCRF/MFOCRF should go through get_crbitm_encoding for the CR operand.
// The GPR operand should come through here though.
assert((MI.getOpcode() != PPC::MTCRF && MI.getOpcode() != PPC::MFOCRF) ||
assert((MI.getOpcode() != PPC::MTCRF && MI.getOpcode() != PPC::MTCRF8 &&
MI.getOpcode() != PPC::MFOCRF && MI.getOpcode() != PPC::MFOCRF8) ||
MO.getReg() < PPC::CR0 || MO.getReg() > PPC::CR7);
return CTX.getRegisterInfo()->getEncodingValue(MO.getReg());
}