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GlobalISel: Combine op undef, x to 0

Browse Source 
https://reviews.llvm.org/D86611
This commit is contained in:
Volkan Keles 2020-09-08 09:46:38 -07:00
parent bcac389fb2
commit c4e63c6e36
4 changed files with 45 additions and 0 deletions
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3
include/llvm/CodeGen/GlobalISel/CombinerHelper.h
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@ -321,6 +321,9 @@ public:
/// Check if operand \p OpIdx is zero.
bool matchOperandIsZero(MachineInstr &MI, unsigned OpIdx);
/// Check if operand \p OpIdx is undef.
bool matchOperandIsUndef(MachineInstr &MI, unsigned OpIdx);
/// Erase \p MI
bool eraseInst(MachineInstr &MI);

7
include/llvm/Target/GlobalISel/Combine.td
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@ -194,6 +194,12 @@ def undef_to_negative_one: GICombineRule<
[{ return Helper.matchAnyExplicitUseIsUndef(*${root}); }]),
(apply [{ Helper.replaceInstWithConstant(*${root}, -1); }])>;
def binop_left_undef_to_zero: GICombineRule<
(defs root:$root),
(match (wip_match_opcode G_SHL):$root,
[{ return Helper.matchOperandIsUndef(*${root}, 1); }]),
(apply [{ Helper.replaceInstWithConstant(*${root}, 0); }])>;
// Instructions where if any source operand is undef, the instruction can be
// replaced with undef.
def propagate_undef_any_op: GICombineRule<
@ -384,6 +390,7 @@ def not_cmp_fold : GICombineRule<
// FIXME: These should use the custom predicate feature once it lands.
def undef_combines : GICombineGroup<[undef_to_fp_zero, undef_to_int_zero,
undef_to_negative_one,
binop_left_undef_to_zero,
propagate_undef_any_op,
propagate_undef_all_ops,
propagate_undef_shuffle_mask,

6
lib/CodeGen/GlobalISel/CombinerHelper.cpp
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@ -1989,6 +1989,12 @@ bool CombinerHelper::matchOperandIsZero(MachineInstr &MI, unsigned OpIdx) {
MRI);
}
bool CombinerHelper::matchOperandIsUndef(MachineInstr &MI, unsigned OpIdx) {
MachineOperand &MO = MI.getOperand(OpIdx);
return MO.isReg() &&
getOpcodeDef(TargetOpcode::G_IMPLICIT_DEF, MO.getReg(), MRI);
}
bool CombinerHelper::replaceInstWithFConstant(MachineInstr &MI, double C) {
assert(MI.getNumDefs() == 1 && "Expected only one def?");
Builder.setInstr(MI);

29
test/CodeGen/AArch64/GlobalISel/combine-shl.mir Normal file
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@ -0,0 +1,29 @@
# 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>)
...