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Differential D135020

[GlobalISel] Combine `undef / X -> 0` and `undef % X -> 0`
ClosedPublic

Authored by paquette on Oct 1 2022, 1:42 PM.

Details

Reviewers
aemerson
jroelofs
arsenm
Commits
rG24553df57dcc: [GlobalISel] Combine `undef / X -> 0` and `undef % X -> 0`
Summary

This fixes the urem_undef_lhs case in the following:

https://gcc.godbolt.org/z/Wo9x7o679

Also see https://github.com/llvm/llvm-project/issues/57256 for more related bugs.

This is equivalent to the undef bits in simplifyDivRem in the DAGCombiner.

Diff Detail

Event Timeline

paquette created this revision.Oct 1 2022, 1:42 PM
Herald added a project: Restricted Project. · View Herald TranscriptOct 1 2022, 1:42 PM
Herald added subscribers: steven.zhang, rovka. · View Herald Transcript
paquette requested review of this revision.Oct 1 2022, 1:42 PM
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arsenm accepted this revision.Oct 1 2022, 1:48 PM
This revision is now accepted and ready to land.Oct 1 2022, 1:48 PM
This revision was landed with ongoing or failed builds.Oct 1 2022, 1:49 PM
Closed by commit rG24553df57dcc: [GlobalISel] Combine `undef / X -> 0` and `undef % X -> 0` (authored by paquette). · Explain Why
This revision was automatically updated to reflect the committed changes.
paquette added a commit: rG24553df57dcc: [GlobalISel] Combine `undef / X -> 0` and `undef % X -> 0`.
Harbormaster completed remote builds in B189862: Diff 464518.Oct 1 2022, 2:45 PM

Revision Contents

PathSize
llvm/
include/
llvm/
Target/
GlobalISel/
2 lines
test/
CodeGen/
AArch64/
GlobalISel/
94 lines

Diff 464519

llvm/include/llvm/Target/GlobalISel/Combine.td

Show First 20 Lines • Show All 225 Lines • ▼ Show 20 Lines
def undef_to_negative_one: GICombineRule< def undef_to_negative_one: GICombineRule<
(defs root:$root), (defs root:$root),
(match (wip_match_opcode G_OR):$root, (match (wip_match_opcode G_OR):$root,
[{ return Helper.matchAnyExplicitUseIsUndef(*${root}); }]), [{ return Helper.matchAnyExplicitUseIsUndef(*${root}); }]),
(apply [{ Helper.replaceInstWithConstant(*${root}, -1); }])>; (apply [{ Helper.replaceInstWithConstant(*${root}, -1); }])>;
def binop_left_undef_to_zero: GICombineRule< def binop_left_undef_to_zero: GICombineRule<
(defs root:$root), (defs root:$root),
(match (wip_match_opcode G_SHL):$root, (match (wip_match_opcode G_SHL, G_UDIV, G_UREM):$root,
[{ return Helper.matchOperandIsUndef(*${root}, 1); }]), [{ return Helper.matchOperandIsUndef(*${root}, 1); }]),
(apply [{ Helper.replaceInstWithConstant(*${root}, 0); }])>; (apply [{ Helper.replaceInstWithConstant(*${root}, 0); }])>;
def binop_right_undef_to_undef: GICombineRule< def binop_right_undef_to_undef: GICombineRule<
(defs root:$root), (defs root:$root),
(match (wip_match_opcode G_SHL, G_ASHR, G_LSHR):$root, (match (wip_match_opcode G_SHL, G_ASHR, G_LSHR):$root,
[{ return Helper.matchOperandIsUndef(*${root}, 2); }]), [{ return Helper.matchOperandIsUndef(*${root}, 2); }]),
(apply [{ Helper.replaceInstWithUndef(*${root}); }])>; (apply [{ Helper.replaceInstWithUndef(*${root}); }])>;
▲ Show 20 Lines • Show All 780 Lines • Show Last 20 Lines

llvm/test/CodeGen/AArch64/GlobalISel/combine-binop-undef-left-to-zero.mir

  • This file was added.
# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
# RUN: llc -o - -mtriple=aarch64-unknown-unknown -run-pass=aarch64-prelegalizer-combiner -verify-machineinstrs %s | FileCheck %s
---
name: test_combine_shl_undef_x_s32
body: |
bb.1:
liveins: $w0
; CHECK-LABEL: name: test_combine_shl_undef_x_s32
; CHECK: liveins: $w0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
; CHECK-NEXT: $w0 = COPY [[C]](s32)
%0:_(s32) = COPY $w0
%1:_(s32) = G_IMPLICIT_DEF
%2:_(s32) = G_SHL %1(s32), %0(s32)
$w0 = COPY %2(s32)
...
---
name: test_combine_shl_undef_x_v2s32
body: |
bb.1:
liveins: $d0
; CHECK-LABEL: name: test_combine_shl_undef_x_v2s32
; CHECK: liveins: $d0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
; CHECK-NEXT: [[BUILD_VECTOR:%[0-9]+]]:_(<2 x s32>) = G_BUILD_VECTOR [[C]](s32), [[C]](s32)
; CHECK-NEXT: $d0 = COPY [[BUILD_VECTOR]](<2 x s32>)
%0:_(<2 x s32>) = COPY $d0
%1:_(<2 x s32>) = G_IMPLICIT_DEF
%2:_(<2 x s32>) = G_SHL %1(<2 x s32>), %0(<2 x s32>)
$d0 = COPY %2(<2 x s32>)
...
---
name: udiv_scalar
body: |
bb.1:
liveins: $w0
; CHECK-LABEL: name: udiv_scalar
; CHECK: liveins: $w0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: %op:_(s32) = G_CONSTANT i32 0
; CHECK-NEXT: $w0 = COPY %op(s32)
%rhs:_(s32) = COPY $w0
%undef:_(s32) = G_IMPLICIT_DEF
%op:_(s32) = G_UDIV %undef(s32), %rhs(s32)
$w0 = COPY %op(s32)
...
---
name: udiv_vector
body: |
bb.1:
liveins: $d0
; CHECK-LABEL: name: udiv_vector
; CHECK: liveins: $d0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
; CHECK-NEXT: %op:_(<2 x s32>) = G_BUILD_VECTOR [[C]](s32), [[C]](s32)
; CHECK-NEXT: $d0 = COPY %op(<2 x s32>)
%rhs:_(<2 x s32>) = COPY $d0
%undef:_(<2 x s32>) = G_IMPLICIT_DEF
%op:_(<2 x s32>) = G_UDIV %undef(<2 x s32>), %rhs(<2 x s32>)
$d0 = COPY %op(<2 x s32>)
...
---
name: urem_scalar
body: |
bb.1:
liveins: $w0
; CHECK-LABEL: name: urem_scalar
; CHECK: liveins: $w0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: %op:_(s32) = G_CONSTANT i32 0
; CHECK-NEXT: $w0 = COPY %op(s32)
%rhs:_(s32) = COPY $w0
%undef:_(s32) = G_IMPLICIT_DEF
%op:_(s32) = G_UREM %undef(s32), %rhs(s32)
$w0 = COPY %op(s32)
...
---
name: urem_vector
body: |
bb.1:
liveins: $d0
; CHECK-LABEL: name: urem_vector
; CHECK: liveins: $d0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
; CHECK-NEXT: %op:_(<2 x s32>) = G_BUILD_VECTOR [[C]](s32), [[C]](s32)
; CHECK-NEXT: $d0 = COPY %op(<2 x s32>)
%rhs:_(<2 x s32>) = COPY $d0
%undef:_(<2 x s32>) = G_IMPLICIT_DEF
%op:_(<2 x s32>) = G_UREM %undef(<2 x s32>), %rhs(<2 x s32>)
$d0 = COPY %op(<2 x s32>)

llvm/test/CodeGen/AArch64/GlobalISel/combine-shl.mir

  • This file was deleted.
# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
# RUN: llc -o - -mtriple=aarch64-unknown-unknown -run-pass=aarch64-prelegalizer-combiner -verify-machineinstrs %s | FileCheck %s
---
name: test_combine_shl_undef_x_s32
body: |
bb.1:
liveins: $w0
; CHECK-LABEL: name: test_combine_shl_undef_x_s32
; CHECK: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
; CHECK: $w0 = COPY [[C]](s32)
%0:_(s32) = COPY $w0
%1:_(s32) = G_IMPLICIT_DEF
%2:_(s32) = G_SHL %1(s32), %0(s32)
$w0 = COPY %2(s32)
...
---
name: test_combine_shl_undef_x_v2s32
body: |
bb.1:
liveins: $d0
; CHECK-LABEL: name: test_combine_shl_undef_x_v2s32
; CHECK: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
; CHECK: [[BUILD_VECTOR:%[0-9]+]]:_(<2 x s32>) = G_BUILD_VECTOR [[C]](s32), [[C]](s32)
; CHECK: $d0 = COPY [[BUILD_VECTOR]](<2 x s32>)
%0:_(<2 x s32>) = COPY $d0
%1:_(<2 x s32>) = G_IMPLICIT_DEF
%2:_(<2 x s32>) = G_SHL %1(<2 x s32>), %0(<2 x s32>)
$d0 = COPY %2(<2 x s32>)
...
llvm/test/CodeGen/AArch64/GlobalISel/combine-binop-undef-left-to-zero.mir