1baa385065
In #88217 a large set of matchers was changed to only accept poison values in splats, but not undef values. This is because we now use poison for non-demanded vector elements, and allowing undef can cause correctness issues. This patch covers the remaining matchers by changing the AllowUndef parameter of getSplatValue() to AllowPoison instead. We also carry out corresponding renames in matchers. As a followup, we may want to change the default for things like m_APInt to m_APIntAllowPoison (as this is much less risky when only allowing poison), but this change doesn't do that. There is one caveat here: We have a single place (X86FixupVectorConstants) which does require handling of vector splats with undefs. This is because this works on backend constant pool entries, which currently still use undef instead of poison for non-demanded elements (because SDAG as a whole does not have an explicit poison representation). As it's just the single use, I've open-coded a getSplatValueAllowUndef() helper there, to discourage use in any other places.
170 lines
4.9 KiB
LLVM
170 lines
4.9 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt < %s -passes=instcombine -S | FileCheck %s
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; PR51305: prefer `-(x & 1)` over `(x << (bitwidth(x)-1)) a>> (bitwidth(x)-1)`
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; as the pattern to splat the lowest bit.
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declare void @use8(i8)
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; Basic positive scalar tests
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define i8 @t0(i8 %x) {
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; CHECK-LABEL: @t0(
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; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[X:%.*]], 1
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; CHECK-NEXT: [[R:%.*]] = sub nsw i8 0, [[TMP1]]
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; CHECK-NEXT: ret i8 [[R]]
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;
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%i0 = shl i8 %x, 7
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%r = ashr i8 %i0, 7
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ret i8 %r
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}
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define i16 @t1_otherbitwidth(i16 %x) {
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; CHECK-LABEL: @t1_otherbitwidth(
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; CHECK-NEXT: [[TMP1:%.*]] = and i16 [[X:%.*]], 1
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; CHECK-NEXT: [[R:%.*]] = sub nsw i16 0, [[TMP1]]
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; CHECK-NEXT: ret i16 [[R]]
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;
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%i0 = shl i16 %x, 15
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%r = ashr i16 %i0, 15
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ret i16 %r
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}
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; Basic positive vector tests
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define <2 x i8> @t2_vec(<2 x i8> %x) {
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; CHECK-LABEL: @t2_vec(
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; CHECK-NEXT: [[TMP1:%.*]] = and <2 x i8> [[X:%.*]], <i8 1, i8 1>
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; CHECK-NEXT: [[R:%.*]] = sub nsw <2 x i8> zeroinitializer, [[TMP1]]
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; CHECK-NEXT: ret <2 x i8> [[R]]
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;
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%i0 = shl <2 x i8> %x, <i8 7, i8 7>
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%r = ashr <2 x i8> %i0, <i8 7, i8 7>
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ret <2 x i8> %r
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}
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; TODO: The result constants should contain poison instead of undef.
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define <3 x i8> @t3_vec_poison0(<3 x i8> %x) {
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; CHECK-LABEL: @t3_vec_poison0(
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; CHECK-NEXT: [[TMP1:%.*]] = and <3 x i8> [[X:%.*]], <i8 1, i8 undef, i8 1>
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; CHECK-NEXT: [[R:%.*]] = sub <3 x i8> zeroinitializer, [[TMP1]]
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; CHECK-NEXT: ret <3 x i8> [[R]]
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;
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%i0 = shl <3 x i8> %x, <i8 7, i8 poison, i8 7>
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%r = ashr <3 x i8> %i0, <i8 7, i8 7, i8 7>
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ret <3 x i8> %r
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}
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define <3 x i8> @t4_vec_poison1(<3 x i8> %x) {
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; CHECK-LABEL: @t4_vec_poison1(
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; CHECK-NEXT: [[TMP1:%.*]] = and <3 x i8> [[X:%.*]], <i8 1, i8 undef, i8 1>
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; CHECK-NEXT: [[R:%.*]] = sub <3 x i8> zeroinitializer, [[TMP1]]
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; CHECK-NEXT: ret <3 x i8> [[R]]
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;
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%i0 = shl <3 x i8> %x, <i8 7, i8 7, i8 7>
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%r = ashr <3 x i8> %i0, <i8 7, i8 poison, i8 7>
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ret <3 x i8> %r
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}
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define <3 x i8> @t5_vec_poison2(<3 x i8> %x) {
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; CHECK-LABEL: @t5_vec_poison2(
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; CHECK-NEXT: [[TMP1:%.*]] = and <3 x i8> [[X:%.*]], <i8 1, i8 undef, i8 1>
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; CHECK-NEXT: [[R:%.*]] = sub <3 x i8> zeroinitializer, [[TMP1]]
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; CHECK-NEXT: ret <3 x i8> [[R]]
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;
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%i0 = shl <3 x i8> %x, <i8 7, i8 poison, i8 7>
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%r = ashr <3 x i8> %i0, <i8 7, i8 poison, i8 7>
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ret <3 x i8> %r
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}
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; In general, the `shl` needs to go away.
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define i8 @n6_extrause(i8 %x) {
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; CHECK-LABEL: @n6_extrause(
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; CHECK-NEXT: [[I0:%.*]] = shl i8 [[X:%.*]], 7
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; CHECK-NEXT: call void @use8(i8 [[I0]])
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; CHECK-NEXT: [[R:%.*]] = ashr exact i8 [[I0]], 7
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; CHECK-NEXT: ret i8 [[R]]
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;
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%i0 = shl i8 %x, 7
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call void @use8(i8 %i0)
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%r = ashr i8 %i0, 7
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ret i8 %r
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}
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; But, if the input to the shift is already masked, then we're fine.
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define i8 @t7_already_masked(i8 %x) {
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; CHECK-LABEL: @t7_already_masked(
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; CHECK-NEXT: [[I0:%.*]] = and i8 [[X:%.*]], 1
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; CHECK-NEXT: call void @use8(i8 [[I0]])
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; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[X]], 1
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; CHECK-NEXT: [[R:%.*]] = sub nsw i8 0, [[TMP1]]
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; CHECK-NEXT: ret i8 [[R]]
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;
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%i0 = and i8 %x, 1
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call void @use8(i8 %i0)
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%i1 = shl i8 %i0, 7
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%r = ashr i8 %i1, 7
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ret i8 %r
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}
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; FIXME: we should fold this
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define i8 @t8_already_masked_extrause(i8 %x) {
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; CHECK-LABEL: @t8_already_masked_extrause(
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; CHECK-NEXT: [[I0:%.*]] = and i8 [[X:%.*]], 1
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; CHECK-NEXT: call void @use8(i8 [[I0]])
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; CHECK-NEXT: [[I1:%.*]] = shl i8 [[X]], 7
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; CHECK-NEXT: call void @use8(i8 [[I1]])
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; CHECK-NEXT: [[R:%.*]] = ashr exact i8 [[I1]], 7
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; CHECK-NEXT: ret i8 [[R]]
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;
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%i0 = and i8 %x, 1
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call void @use8(i8 %i0)
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%i1 = shl i8 %i0, 7
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call void @use8(i8 %i1)
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%r = ashr i8 %i1, 7
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ret i8 %r
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}
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define i8 @n9_wrongly_masked_extrause(i8 %x) {
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; CHECK-LABEL: @n9_wrongly_masked_extrause(
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; CHECK-NEXT: [[I0:%.*]] = and i8 [[X:%.*]], 3
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; CHECK-NEXT: call void @use8(i8 [[I0]])
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; CHECK-NEXT: [[I1:%.*]] = shl i8 [[X]], 7
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; CHECK-NEXT: call void @use8(i8 [[I1]])
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; CHECK-NEXT: [[R:%.*]] = ashr exact i8 [[I1]], 7
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; CHECK-NEXT: ret i8 [[R]]
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;
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%i0 = and i8 %x, 3
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call void @use8(i8 %i0)
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%i1 = shl i8 %i0, 7
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call void @use8(i8 %i1)
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%r = ashr i8 %i1, 7
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ret i8 %r
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}
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; Wrong shift amounts
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define i8 @n10(i8 %x) {
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; CHECK-LABEL: @n10(
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; CHECK-NEXT: [[I0:%.*]] = shl i8 [[X:%.*]], 6
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; CHECK-NEXT: [[R:%.*]] = ashr i8 [[I0]], 7
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; CHECK-NEXT: ret i8 [[R]]
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;
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%i0 = shl i8 %x, 6 ; not 7
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%r = ashr i8 %i0, 7
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ret i8 %r
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}
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define i8 @n11(i8 %x) {
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; CHECK-LABEL: @n11(
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; CHECK-NEXT: [[I0:%.*]] = shl i8 [[X:%.*]], 7
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; CHECK-NEXT: [[R:%.*]] = ashr exact i8 [[I0]], 6
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; CHECK-NEXT: ret i8 [[R]]
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;
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%i0 = shl i8 %x, 7
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%r = ashr i8 %i0, 6 ; not 7
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ret i8 %r
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}
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define i8 @n12(i8 %x) {
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; CHECK-LABEL: @n12(
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; CHECK-NEXT: [[I0:%.*]] = shl i8 [[X:%.*]], 6
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; CHECK-NEXT: [[R:%.*]] = ashr exact i8 [[I0]], 6
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; CHECK-NEXT: ret i8 [[R]]
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;
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%i0 = shl i8 %x, 6 ; not 7
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%r = ashr i8 %i0, 6 ; not 7
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ret i8 %r
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}
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