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[AArch64InstrInfo] Ignore debug insts in areCFlagsAccessedBetweenInstrs [7/14]

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Summary:
Fix an issue where the presence of debug info could disable a peephole
optimization due to areCFlagsAccessedBetweenInstrs returning the wrong
result.

In test/CodeGen/AArch64/arm64-csel.ll, the issue was found in the
function @foo5, in which the first compare could successfully be
optimized but not the second.

Reviewers: t.p.northover, eastig, paquette

Subscribers: kristof.beyls, hiraditya, danielkiss, aprantl, dsanders, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D78157
This commit is contained in:
Vedant Kumar 2020-04-14 14:50:03 -07:00
parent aa227fa99f
commit ee83cda2e4
3 changed files with 5 additions and 5 deletions
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1
lib/CodeGen/PeepholeOptimizer.cpp
View File

@ -616,6 +616,7 @@ bool PeepholeOptimizer::optimizeCmpInstr(MachineInstr &MI) {
// Attempt to optimize the comparison instruction.
LLVM_DEBUG(dbgs() << "Attempting to optimize compare: " << MI);
if (TII->optimizeCompareInstr(MI, SrcReg, SrcReg2, CmpMask, CmpValue, MRI)) {
LLVM_DEBUG(dbgs() << " -> Successfully optimized compare!\n");
++NumCmps;
return true;
}

7
lib/Target/AArch64/AArch64InstrInfo.cpp
View File

@ -1183,10 +1183,9 @@ static bool areCFlagsAccessedBetweenInstrs(
return MI.getIterator() == From;
}) != To->getParent()->rend());
// We iterate backward starting \p To until we hit \p From.
for (--To; To != From; --To) {
const MachineInstr &Instr = *To;
// We iterate backward starting at \p To until we hit \p From.
for (const MachineInstr &Instr :
reversedInstructionsWithoutDebug(std::prev(To), From)) {
if (((AccessToCheck & AK_Write) &&
Instr.modifiesRegister(AArch64::NZCV, TRI)) ||
((AccessToCheck & AK_Read) && Instr.readsRegister(AArch64::NZCV, TRI)))

2
test/CodeGen/AArch64/arm64-csel.ll
View File

@ -1,4 +1,4 @@
; RUN: llc -O3 < %s | FileCheck %s
; RUN: llc -debugify-and-strip-all-safe -O3 < %s | FileCheck %s
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-n32:64"
target triple = "arm64-unknown-unknown"