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[GlobalISel] Combine [s,z]ext of undef into 0 #117439

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Merged
merged 3 commits into from
Dec 3, 2024
Merged

[GlobalISel] Combine [s,z]ext of undef into 0 #117439

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[GlobalISel] Combine [a,s,z]ext of undef into 0 or undef
tschuett Nov 23, 2024
2fdf196
return true;
tschuett Nov 30, 2024
59422fe
remove return true;
tschuett Nov 30, 2024
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27 changes: 25 additions & 2 deletions llvm/include/llvm/Target/GlobalISel/Combine.td
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Expand Up @@ -428,7 +428,7 @@ def unary_undef_to_zero: GICombineRule<
// replaced with undef.
def propagate_undef_any_op: GICombineRule<
(defs root:$root),
(match (wip_match_opcode G_ADD, G_FPTOSI, G_FPTOUI, G_SUB, G_XOR, G_TRUNC, G_BITCAST, G_ANYEXT):$root,
(match (wip_match_opcode G_ADD, G_FPTOSI, G_FPTOUI, G_SUB, G_XOR, G_TRUNC, G_BITCAST):$root,
[{ return Helper.matchAnyExplicitUseIsUndef(*${root}); }]),
(apply [{ Helper.replaceInstWithUndef(*${root}); }])>;

Expand Down Expand Up @@ -1857,6 +1857,26 @@ class integer_of_opcode<Instruction castOpcode> : GICombineRule <

def integer_of_truncate : integer_of_opcode<G_TRUNC>;

def anyext_undef: GICombineRule<
(defs root:$root),
(match (G_IMPLICIT_DEF $undef),
(G_ANYEXT $root, $undef):$Aext),
(apply [{ Helper.replaceInstWithUndef(*${Aext}); }])>;
Comment on lines +1860 to +1864
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Why is this change still here at all? It was fine where it was in propagate_undef_any_op.

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Helper.matchAnyExplicitUseIsUndef checks in C++, if there is an undef on the anyext. It will fail 99.999999999999% of the time. Now it is a correct pattern and the combiner takes care of the matching.

I said in the summary Is there a limit on the number of patterns?.

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You can leave it where it is, and we can have another PR to convert propagate_undef_any_op into the new match syntax for all opcodes, not just undef. This PR is an optimization which is now mixing a refactoring. I'm going to approve this PR on the assumption that you leave undef combine where it is until we convert them en-mass.


def zext_undef: GICombineRule<
(defs root:$root),
(match (G_IMPLICIT_DEF $undef),
(G_ZEXT $root, $undef):$Zext,
[{ return Helper.isConstantLegalOrBeforeLegalizer(MRI.getType(${Zext}->getOperand(0).getReg())); }]),
(apply [{ Helper.replaceInstWithConstant(*${Zext}, 0); }])>;

def sext_undef: GICombineRule<
(defs root:$root),
(match (G_IMPLICIT_DEF $undef),
(G_SEXT $root, $undef):$Sext,
[{ return Helper.isConstantLegalOrBeforeLegalizer(MRI.getType(${Sext}->getOperand(0).getReg())); }]),
(apply [{ Helper.replaceInstWithConstant(*${Sext}, 0); }])>;

def cast_of_cast_combines: GICombineGroup<[
truncate_of_zext,
truncate_of_sext,
Expand All @@ -1882,7 +1902,10 @@ def cast_combines: GICombineGroup<[
narrow_binop_and,
narrow_binop_or,
narrow_binop_xor,
integer_of_truncate
integer_of_truncate,
anyext_undef,
sext_undef,
zext_undef
]>;

def canonicalize_icmp : GICombineRule<
Expand Down
52 changes: 52 additions & 0 deletions llvm/test/CodeGen/AArch64/GlobalISel/combine-cast.mir
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Expand Up @@ -217,3 +217,55 @@ body: |
%large:_(<2 x s64>) = G_ANYEXT %bv(<2 x s32>)
$q0 = COPY %large(<2 x s64>)
$d0 = COPY %bv(<2 x s32>)
...
---
name: test_combine_anyext_undef
legalized: true
body: |
bb.1:
; CHECK-PRE-LABEL: name: test_combine_anyext_undef
; CHECK-PRE: %aext:_(s64) = G_IMPLICIT_DEF
; CHECK-PRE-NEXT: $x0 = COPY %aext(s64)
;
; CHECK-POST-LABEL: name: test_combine_anyext_undef
; CHECK-POST: %undef:_(s32) = G_IMPLICIT_DEF
; CHECK-POST-NEXT: %aext:_(s64) = G_ANYEXT %undef(s32)
; CHECK-POST-NEXT: $x0 = COPY %aext(s64)
%undef:_(s32) = G_IMPLICIT_DEF
%aext:_(s64) = G_ANYEXT %undef(s32)
$x0 = COPY %aext(s64)
...
---
name: test_combine_sext_undef
legalized: true
body: |
bb.1:
; CHECK-PRE-LABEL: name: test_combine_sext_undef
; CHECK-PRE: %sext:_(s64) = G_CONSTANT i64 0
; CHECK-PRE-NEXT: $x0 = COPY %sext(s64)
;
; CHECK-POST-LABEL: name: test_combine_sext_undef
; CHECK-POST: %undef:_(s32) = G_IMPLICIT_DEF
; CHECK-POST-NEXT: %sext:_(s64) = G_SEXT %undef(s32)
; CHECK-POST-NEXT: $x0 = COPY %sext(s64)
%undef:_(s32) = G_IMPLICIT_DEF
%sext:_(s64) = G_SEXT %undef(s32)
$x0 = COPY %sext(s64)
...
---
name: test_combine_zext_undef
legalized: true
body: |
bb.1:
; CHECK-PRE-LABEL: name: test_combine_zext_undef
; CHECK-PRE: %zext:_(s64) = G_CONSTANT i64 0
; CHECK-PRE-NEXT: $x0 = COPY %zext(s64)
;
; CHECK-POST-LABEL: name: test_combine_zext_undef
; CHECK-POST: %undef:_(s32) = G_IMPLICIT_DEF
; CHECK-POST-NEXT: %zext:_(s64) = G_ZEXT %undef(s32)
; CHECK-POST-NEXT: $x0 = COPY %zext(s64)
%undef:_(s32) = G_IMPLICIT_DEF
%zext:_(s64) = G_ZEXT %undef(s32)
$x0 = COPY %zext(s64)
...
15 changes: 4 additions & 11 deletions llvm/test/CodeGen/AArch64/extract-vector-elt.ll
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Expand Up @@ -8,17 +8,10 @@
; CHECK-GI-NEXT: warning: Instruction selection used fallback path for extract_v4i32_vector_extract_const

define i64 @extract_v2i64_undef_index(<2 x i64> %a, i32 %c) {
; CHECK-SD-LABEL: extract_v2i64_undef_index:
; CHECK-SD: // %bb.0: // %entry
; CHECK-SD-NEXT: fmov x0, d0
; CHECK-SD-NEXT: ret
;
; CHECK-GI-LABEL: extract_v2i64_undef_index:
; CHECK-GI: // %bb.0: // %entry
; CHECK-GI-NEXT: str q0, [sp, #-16]!
; CHECK-GI-NEXT: .cfi_def_cfa_offset 16
; CHECK-GI-NEXT: ldr x0, [sp], #16
; CHECK-GI-NEXT: ret
; CHECK-LABEL: extract_v2i64_undef_index:
; CHECK: // %bb.0: // %entry
; CHECK-NEXT: fmov x0, d0
; CHECK-NEXT: ret
entry:
%d = extractelement <2 x i64> %a, i32 undef
ret i64 %d
Expand Down
6 changes: 2 additions & 4 deletions llvm/test/CodeGen/AMDGPU/GlobalISel/combine-amdgpu-cvt-f32-ubyte.mir
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Expand Up @@ -261,8 +261,7 @@ body: |
; CHECK-LABEL: name: cvt_f32_ubyte0_zext_lshr_16
; CHECK: liveins: $vgpr0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: %shift:_(s16) = G_IMPLICIT_DEF
; CHECK-NEXT: %zext:_(s32) = G_ZEXT %shift(s16)
; CHECK-NEXT: %zext:_(s32) = G_CONSTANT i32 0
; CHECK-NEXT: %result:_(s32) = G_AMDGPU_CVT_F32_UBYTE0 %zext
; CHECK-NEXT: $vgpr0 = COPY %result(s32)
%arg:_(s32) = COPY $vgpr0
Expand All @@ -284,8 +283,7 @@ body: |
; CHECK-LABEL: name: cvt_f32_ubyte0_zext_lshr_24
; CHECK: liveins: $vgpr0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: %shift:_(s16) = G_IMPLICIT_DEF
; CHECK-NEXT: %zext:_(s32) = G_ZEXT %shift(s16)
; CHECK-NEXT: %zext:_(s32) = G_CONSTANT i32 0
; CHECK-NEXT: %result:_(s32) = G_AMDGPU_CVT_F32_UBYTE0 %zext
; CHECK-NEXT: $vgpr0 = COPY %result(s32)
%arg:_(s32) = COPY $vgpr0
Expand Down
7 changes: 1 addition & 6 deletions llvm/test/CodeGen/AMDGPU/shrink-add-sub-constant.ll
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Expand Up @@ -4074,14 +4074,12 @@ define amdgpu_kernel void @v_test_v2i16_x_add_undef_neg32(ptr addrspace(1) %out,
; VI-GISEL-NEXT: v_addc_u32_e32 v1, vcc, 0, v1, vcc
; VI-GISEL-NEXT: flat_load_dword v3, v[0:1]
; VI-GISEL-NEXT: v_mov_b32_e32 v0, s0
; VI-GISEL-NEXT: v_mov_b32_e32 v1, s1
; VI-GISEL-NEXT: v_add_u32_e32 v0, vcc, v0, v2
; VI-GISEL-NEXT: v_not_b32_e32 v2, 31
; VI-GISEL-NEXT: v_mov_b32_e32 v1, s1
; VI-GISEL-NEXT: s_and_b32 s0, 0xffff, s0
; VI-GISEL-NEXT: v_addc_u32_e32 v1, vcc, 0, v1, vcc
; VI-GISEL-NEXT: s_waitcnt vmcnt(0)
; VI-GISEL-NEXT: v_add_u16_sdwa v2, v3, v2 dst_sel:WORD_1 dst_unused:UNUSED_PAD src0_sel:WORD_1 src1_sel:DWORD
; VI-GISEL-NEXT: v_or_b32_e32 v2, s0, v2
; VI-GISEL-NEXT: flat_store_dword v[0:1], v2
; VI-GISEL-NEXT: s_endpgm
;
Expand Down Expand Up @@ -4191,15 +4189,12 @@ define amdgpu_kernel void @v_test_v2i16_x_add_neg32_undef(ptr addrspace(1) %out,
; VI-GISEL-NEXT: v_add_u32_e32 v0, vcc, v0, v2
; VI-GISEL-NEXT: v_addc_u32_e32 v1, vcc, 0, v1, vcc
; VI-GISEL-NEXT: flat_load_dword v3, v[0:1]
; VI-GISEL-NEXT: s_and_b32 s2, 0xffff, s0
; VI-GISEL-NEXT: v_mov_b32_e32 v0, s0
; VI-GISEL-NEXT: v_mov_b32_e32 v1, s1
; VI-GISEL-NEXT: v_add_u32_e32 v0, vcc, v0, v2
; VI-GISEL-NEXT: s_lshl_b32 s0, s2, 16
; VI-GISEL-NEXT: v_addc_u32_e32 v1, vcc, 0, v1, vcc
; VI-GISEL-NEXT: s_waitcnt vmcnt(0)
; VI-GISEL-NEXT: v_add_u16_e32 v2, 0xffe0, v3
; VI-GISEL-NEXT: v_or_b32_e32 v2, s0, v2
; VI-GISEL-NEXT: flat_store_dword v[0:1], v2
; VI-GISEL-NEXT: s_endpgm
;
Expand Down
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