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[AArch64] Avoid adding duplicate implicit operands when expanding pseudo insts. 

When expanding pseudo insts, in order to create a new machine instr, we use BuildMI,
which will add implicit operands by default. And transferImpOps will also copy implicit
operands from old ones. Finally, duplicate implicit operands are added to the same inst.
Sometimes this can cause correctness issues. Like below inst,
    renamable $w18 = nsw SUBSWrr renamable $w30, renamable $w14, implicit-def dead $nzcv
After expanding, it will become
    $w18 = SUBSWrs renamable $w13, renamable $w14, 0, implicit-def $nzcv, implicit-def dead $nzcv
A redundant implicit-def $nzcv is added, but the dead flag is missing.

Reviewed By: dmgreen

Differential Revision: https://reviews.llvm.org/D109069
This commit is contained in:
Andrew Wei 2021-09-07 17:05:39 +08:00
parent a40599c97b
commit da9ed3dc71
2 changed files with 31 additions and 6 deletions
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16
llvm/lib/Target/AArch64/AArch64ExpandPseudoInsts.cpp
View File

@ -937,12 +937,16 @@ bool AArch64ExpandPseudo::expandMI(MachineBasicBlock &MBB,
case AArch64::ORRWrr: Opcode = AArch64::ORRWrs; break;
case AArch64::ORRXrr: Opcode = AArch64::ORRXrs; break;
}
MachineInstrBuilder MIB1 =
BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(Opcode),
MI.getOperand(0).getReg())
.add(MI.getOperand(1))
.add(MI.getOperand(2))
.addImm(AArch64_AM::getShifterImm(AArch64_AM::LSL, 0));
MachineFunction &MF = *MBB.getParent();
// Try to create new inst without implicit operands added.
MachineInstr *NewMI = MF.CreateMachineInstr(
TII->get(Opcode), MI.getDebugLoc(), /*NoImplicit=*/true);
MBB.insert(MBBI, NewMI);
MachineInstrBuilder MIB1(MF, NewMI);
MIB1.addReg(MI.getOperand(0).getReg(), RegState::Define)
.add(MI.getOperand(1))
.add(MI.getOperand(2))
.addImm(AArch64_AM::getShifterImm(AArch64_AM::LSL, 0));
transferImpOps(MI, MIB1, MIB1);
MI.eraseFromParent();
return true;

21
llvm/test/CodeGen/AArch64/expand-subs-pseudo.mir Normal file
View File

@ -0,0 +1,21 @@
# RUN: llc -run-pass=aarch64-expand-pseudo -mtriple=aarch64-unknown-linux-gnu -o - %s | FileCheck %s
---
# CHECK-LABEL: name: test
# CHECK-LABEL: bb.0:
# CHECK: $w5 = SUBSWrs renamable $w3, renamable $w2, 0, implicit-def dead $nzcv
# CHECK-NEXT: $w6 = SUBSWrs renamable $w5, renamable $w3, 0, implicit-def $nzcv
# CHECK-NEXT: RET undef $lr
#
name: test
alignment: 4
tracksRegLiveness: true
body: |
bb.0:
liveins: $w5, $w6, $x2, $x3
renamable $w5 = nsw SUBSWrr renamable $w3, renamable $w2, implicit-def dead $nzcv
renamable $w6 = nsw SUBSWrr renamable $w5, renamable $w3, implicit-def $nzcv
RET_ReallyLR
...