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| author | Matthias Braun <matthiasb@fb.com> | 2021-09-27 17:57:22 -0700 |
|---|---|---|
| committer | Matthias Braun <matze@braunis.de> | 2022-01-11 09:07:29 -0800 |
| commit | ad25f8a556d239d8b7d17383cf1a0771359521fd (patch) | |
| tree | 93eb034f7cbf67f9f4a294b10f8955c077c2eff7 /llvm/lib/Target/X86/X86InstrInfo.h | |
| parent | be1cc64cc13cb24bcd9ed097925a140d74beaa45 (diff) | |
| download | llvm-optimize_compinstr_fix.tar.gz | |
X86InstrInfo: Support immediates that are +1/-1 different in optimizeCompareInstroptimize_compinstr_fix
This is a re-commit of e2c7ee0743592e39274e28dbe0d0c213ba342317 which
was reverted in a2a58d91e82db38fbdf88cc317dcb3753d79d492 and
ea81cea8163a1a0e54df42103ee1c657bbf03791. This includes a fix to
consistently check for EFLAGS being live-out. See phabricator
review.
Original Summary:
This extends `optimizeCompareInstr` to re-use previous comparison
results if the previous comparison was with an immediate that was 1
bigger or smaller. Example:
CMP x, 13
...
CMP x, 12 ; can be removed if we change the SETg
SETg ... ; x > 12 changed to `SETge` (x >= 13) removing CMP
Motivation: This often happens because SelectionDAG canonicalization
tends to add/subtract 1 often when optimizing for fallthrough blocks.
Example for `x > C` the fallthrough optimization switches true/false
blocks with `!(x > C)` --> `x <= C` and canonicalization turns this into
`x < C + 1`.
Differential Revision: https://reviews.llvm.org/D110867
Diffstat (limited to 'llvm/lib/Target/X86/X86InstrInfo.h')
| -rw-r--r-- | llvm/lib/Target/X86/X86InstrInfo.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/llvm/lib/Target/X86/X86InstrInfo.h b/llvm/lib/Target/X86/X86InstrInfo.h index 537ada6222bf..33ce55bbdb2b 100644 --- a/llvm/lib/Target/X86/X86InstrInfo.h +++ b/llvm/lib/Target/X86/X86InstrInfo.h @@ -643,7 +643,8 @@ private: /// CMP %1, %2 and %3 = SUB %2, %1 ; IsSwapped=true bool isRedundantFlagInstr(const MachineInstr &FlagI, Register SrcReg, Register SrcReg2, int64_t ImmMask, int64_t ImmValue, - const MachineInstr &OI, bool *IsSwapped) const; + const MachineInstr &OI, bool *IsSwapped, + int64_t *ImmDelta) const; }; } // namespace llvm |