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BPF: Fix misfolding subregisters (#208244)

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This would end up introducing a copy between registers
with mismatched sizes previously. Defends against verifier
failures in a future change.

The actual transform here should be deleted. Optimizations should
not be trying to introduce SUBREG_TO_REG.
This commit is contained in:
Matt Arsenault 2026-07-09 22:18:30 +02:00 committed by GitHub
parent 766161cd2f
commit 720066abc2
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2 changed files with 49 additions and 1 deletions
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6
llvm/lib/Target/BPF/BPFMIPeephole.cpp
View file

@ -155,7 +155,11 @@ bool BPFMIPeephole::isInsnFrom32Def(MachineInstr *DefInsn)
bool BPFMIPeephole::isMovFrom32Def(MachineInstr *MovMI)
{
MachineInstr *DefInsn = MRI->getVRegDef(MovMI->getOperand(1).getReg());
const MachineOperand &Src = MovMI->getOperand(1);
if (Src.getSubReg())
return false;
MachineInstr *DefInsn = MRI->getVRegDef(Src.getReg());
LLVM_DEBUG(dbgs() << " Def of Mov Src:");
LLVM_DEBUG(DefInsn->dump());

44
llvm/test/CodeGen/BPF/mov32-64-subreg-source.mir Normal file
View file

@ -0,0 +1,44 @@
# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 6
# RUN: llc -mtriple=bpfel -mattr=+alu32 -run-pass=bpf-mi-zext-elim -verify-machineinstrs %s -o - | FileCheck %s
...
# Make sure that folds of MOV_32_64 respect a subregister index on the
# source operand.
---
name: mov32_64_subreg_source_imm
tracksRegLiveness: true
body: |
bb.0:
liveins: $r1
; CHECK-LABEL: name: mov32_64_subreg_source_imm
; CHECK: liveins: $r1
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: [[LD_imm64_:%[0-9]+]]:gpr = LD_imm64 0
; CHECK-NEXT: [[MOV_32_64_:%[0-9]+]]:gpr = MOV_32_64 [[LD_imm64_]].sub_32
; CHECK-NEXT: $r0 = COPY [[MOV_32_64_]]
; CHECK-NEXT: RET implicit $r0
%0:gpr = LD_imm64 0
%1:gpr = MOV_32_64 %0.sub_32
$r0 = COPY %1:gpr
RET implicit $r0
...
---
name: mov32_64_subreg_source_copy
tracksRegLiveness: true
body: |
bb.0:
liveins: $r1
; CHECK-LABEL: name: mov32_64_subreg_source_copy
; CHECK: liveins: $r1
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: [[COPY:%[0-9]+]]:gpr = COPY $r1
; CHECK-NEXT: [[MOV_32_64_:%[0-9]+]]:gpr = MOV_32_64 [[COPY]].sub_32
; CHECK-NEXT: $r0 = COPY [[MOV_32_64_]]
; CHECK-NEXT: RET implicit $r0
%0:gpr = COPY $r1
%1:gpr = MOV_32_64 %0.sub_32
$r0 = COPY %1:gpr
RET implicit $r0
...