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https://github.com/RPCS3/llvm-mirror.git
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0ac027152c
Poison allows us to return a better result than undef. llvm-svn: 315595
617 lines
15 KiB
LLVM
617 lines
15 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt < %s -instsimplify -S | FileCheck %s
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; Fold icmp with a constant operand.
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define i1 @tautological_ule(i8 %x) {
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; CHECK-LABEL: @tautological_ule(
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; CHECK-NEXT: ret i1 true
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;
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%cmp = icmp ule i8 %x, 255
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ret i1 %cmp
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}
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define <2 x i1> @tautological_ule_vec(<2 x i8> %x) {
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; CHECK-LABEL: @tautological_ule_vec(
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; CHECK-NEXT: ret <2 x i1> <i1 true, i1 true>
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;
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%cmp = icmp ule <2 x i8> %x, <i8 255, i8 255>
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ret <2 x i1> %cmp
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}
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define i1 @tautological_ugt(i8 %x) {
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; CHECK-LABEL: @tautological_ugt(
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; CHECK-NEXT: ret i1 false
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;
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%cmp = icmp ugt i8 %x, 255
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ret i1 %cmp
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}
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define <2 x i1> @tautological_ugt_vec(<2 x i8> %x) {
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; CHECK-LABEL: @tautological_ugt_vec(
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; CHECK-NEXT: ret <2 x i1> zeroinitializer
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;
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%cmp = icmp ugt <2 x i8> %x, <i8 255, i8 255>
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ret <2 x i1> %cmp
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}
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; 'urem x, C2' produces [0, C2)
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define i1 @urem3(i32 %X) {
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; CHECK-LABEL: @urem3(
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; CHECK-NEXT: ret i1 true
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;
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%A = urem i32 %X, 10
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%B = icmp ult i32 %A, 15
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ret i1 %B
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}
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define <2 x i1> @urem3_vec(<2 x i32> %X) {
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; CHECK-LABEL: @urem3_vec(
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; CHECK-NEXT: ret <2 x i1> <i1 true, i1 true>
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;
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%A = urem <2 x i32> %X, <i32 10, i32 10>
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%B = icmp ult <2 x i32> %A, <i32 15, i32 15>
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ret <2 x i1> %B
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}
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;'srem x, C2' produces (-|C2|, |C2|)
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define i1 @srem1(i32 %X) {
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; CHECK-LABEL: @srem1(
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; CHECK-NEXT: ret i1 false
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;
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%A = srem i32 %X, -5
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%B = icmp sgt i32 %A, 5
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ret i1 %B
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}
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define <2 x i1> @srem1_vec(<2 x i32> %X) {
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; CHECK-LABEL: @srem1_vec(
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; CHECK-NEXT: ret <2 x i1> zeroinitializer
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;
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%A = srem <2 x i32> %X, <i32 -5, i32 -5>
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%B = icmp sgt <2 x i32> %A, <i32 5, i32 5>
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ret <2 x i1> %B
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}
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;'udiv C2, x' produces [0, C2]
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define i1 @udiv5(i32 %X) {
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; CHECK-LABEL: @udiv5(
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; CHECK-NEXT: ret i1 false
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;
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%A = udiv i32 123, %X
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%C = icmp ugt i32 %A, 124
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ret i1 %C
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}
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define <2 x i1> @udiv5_vec(<2 x i32> %X) {
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; CHECK-LABEL: @udiv5_vec(
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; CHECK-NEXT: ret <2 x i1> zeroinitializer
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;
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%A = udiv <2 x i32> <i32 123, i32 123>, %X
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%C = icmp ugt <2 x i32> %A, <i32 124, i32 124>
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ret <2 x i1> %C
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}
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; 'udiv x, C2' produces [0, UINT_MAX / C2]
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define i1 @udiv1(i32 %X) {
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; CHECK-LABEL: @udiv1(
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; CHECK-NEXT: ret i1 true
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;
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%A = udiv i32 %X, 1000000
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%B = icmp ult i32 %A, 5000
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ret i1 %B
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}
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define <2 x i1> @udiv1_vec(<2 x i32> %X) {
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; CHECK-LABEL: @udiv1_vec(
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; CHECK-NEXT: ret <2 x i1> <i1 true, i1 true>
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;
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%A = udiv <2 x i32> %X, <i32 1000000, i32 1000000>
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%B = icmp ult <2 x i32> %A, <i32 5000, i32 5000>
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ret <2 x i1> %B
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}
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; 'sdiv C2, x' produces [-|C2|, |C2|]
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define i1 @compare_dividend(i32 %a) {
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; CHECK-LABEL: @compare_dividend(
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; CHECK-NEXT: ret i1 false
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;
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%div = sdiv i32 2, %a
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%cmp = icmp eq i32 %div, 3
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ret i1 %cmp
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}
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define <2 x i1> @compare_dividend_vec(<2 x i32> %a) {
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; CHECK-LABEL: @compare_dividend_vec(
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; CHECK-NEXT: ret <2 x i1> zeroinitializer
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;
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%div = sdiv <2 x i32> <i32 2, i32 2>, %a
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%cmp = icmp eq <2 x i32> %div, <i32 3, i32 3>
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ret <2 x i1> %cmp
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}
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; 'sdiv x, C2' produces [INT_MIN / C2, INT_MAX / C2]
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; where C2 != -1 and C2 != 0 and C2 != 1
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define i1 @sdiv1(i32 %X) {
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; CHECK-LABEL: @sdiv1(
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; CHECK-NEXT: ret i1 true
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;
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%A = sdiv i32 %X, 1000000
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%B = icmp slt i32 %A, 3000
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ret i1 %B
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}
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define <2 x i1> @sdiv1_vec(<2 x i32> %X) {
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; CHECK-LABEL: @sdiv1_vec(
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; CHECK-NEXT: ret <2 x i1> <i1 true, i1 true>
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;
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%A = sdiv <2 x i32> %X, <i32 1000000, i32 1000000>
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%B = icmp slt <2 x i32> %A, <i32 3000, i32 3000>
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ret <2 x i1> %B
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}
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; 'shl nuw C2, x' produces [C2, C2 << CLZ(C2)]
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define i1 @shl5(i32 %X) {
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; CHECK-LABEL: @shl5(
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; CHECK-NEXT: ret i1 true
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;
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%sub = shl nuw i32 4, %X
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%cmp = icmp ugt i32 %sub, 3
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ret i1 %cmp
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}
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define <2 x i1> @shl5_vec(<2 x i32> %X) {
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; CHECK-LABEL: @shl5_vec(
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; CHECK-NEXT: ret <2 x i1> <i1 true, i1 true>
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;
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%sub = shl nuw <2 x i32> <i32 4, i32 4>, %X
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%cmp = icmp ugt <2 x i32> %sub, <i32 3, i32 3>
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ret <2 x i1> %cmp
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}
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; 'shl nsw C2, x' produces [C2 << CLO(C2)-1, C2]
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define i1 @shl2(i32 %X) {
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; CHECK-LABEL: @shl2(
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; CHECK-NEXT: ret i1 false
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;
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%sub = shl nsw i32 -1, %X
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%cmp = icmp eq i32 %sub, 31
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ret i1 %cmp
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}
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define <2 x i1> @shl2_vec(<2 x i32> %X) {
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; CHECK-LABEL: @shl2_vec(
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; CHECK-NEXT: ret <2 x i1> zeroinitializer
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;
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%sub = shl nsw <2 x i32> <i32 -1, i32 -1>, %X
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%cmp = icmp eq <2 x i32> %sub, <i32 31, i32 31>
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ret <2 x i1> %cmp
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}
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; 'shl nsw C2, x' produces [C2 << CLO(C2)-1, C2]
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define i1 @shl4(i32 %X) {
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; CHECK-LABEL: @shl4(
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; CHECK-NEXT: ret i1 true
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;
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%sub = shl nsw i32 -1, %X
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%cmp = icmp sle i32 %sub, -1
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ret i1 %cmp
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}
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define <2 x i1> @shl4_vec(<2 x i32> %X) {
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; CHECK-LABEL: @shl4_vec(
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; CHECK-NEXT: ret <2 x i1> <i1 true, i1 true>
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;
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%sub = shl nsw <2 x i32> <i32 -1, i32 -1>, %X
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%cmp = icmp sle <2 x i32> %sub, <i32 -1, i32 -1>
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ret <2 x i1> %cmp
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}
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; 'shl nsw C2, x' produces [C2, C2 << CLZ(C2)-1]
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define i1 @icmp_shl_nsw_1(i64 %a) {
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; CHECK-LABEL: @icmp_shl_nsw_1(
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; CHECK-NEXT: ret i1 true
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;
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%shl = shl nsw i64 1, %a
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%cmp = icmp sge i64 %shl, 0
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ret i1 %cmp
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}
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define <2 x i1> @icmp_shl_nsw_1_vec(<2 x i64> %a) {
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; CHECK-LABEL: @icmp_shl_nsw_1_vec(
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; CHECK-NEXT: ret <2 x i1> <i1 true, i1 true>
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;
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%shl = shl nsw <2 x i64> <i64 1, i64 1>, %a
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%cmp = icmp sge <2 x i64> %shl, zeroinitializer
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ret <2 x i1> %cmp
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}
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; 'shl nsw C2, x' produces [C2 << CLO(C2)-1, C2]
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define i1 @icmp_shl_nsw_neg1(i64 %a) {
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; CHECK-LABEL: @icmp_shl_nsw_neg1(
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; CHECK-NEXT: ret i1 false
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;
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%shl = shl nsw i64 -1, %a
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%cmp = icmp sge i64 %shl, 3
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ret i1 %cmp
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}
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define <2 x i1> @icmp_shl_nsw_neg1_vec(<2 x i64> %a) {
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; CHECK-LABEL: @icmp_shl_nsw_neg1_vec(
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; CHECK-NEXT: ret <2 x i1> zeroinitializer
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;
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%shl = shl nsw <2 x i64> <i64 -1, i64 -1>, %a
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%cmp = icmp sge <2 x i64> %shl, <i64 3, i64 3>
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ret <2 x i1> %cmp
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}
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; 'lshr x, C2' produces [0, UINT_MAX >> C2]
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define i1 @lshr2(i32 %x) {
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; CHECK-LABEL: @lshr2(
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; CHECK-NEXT: ret i1 false
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;
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%s = lshr i32 %x, 30
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%c = icmp ugt i32 %s, 8
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ret i1 %c
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}
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define <2 x i1> @lshr2_vec(<2 x i32> %x) {
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; CHECK-LABEL: @lshr2_vec(
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; CHECK-NEXT: ret <2 x i1> zeroinitializer
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;
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%s = lshr <2 x i32> %x, <i32 30, i32 30>
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%c = icmp ugt <2 x i32> %s, <i32 8, i32 8>
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ret <2 x i1> %c
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}
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; 'lshr C2, x' produces [C2 >> (Width-1), C2]
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define i1 @exact_lshr_ugt_false(i32 %a) {
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; CHECK-LABEL: @exact_lshr_ugt_false(
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; CHECK-NEXT: ret i1 false
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;
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%shr = lshr exact i32 30, %a
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%cmp = icmp ult i32 %shr, 15
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ret i1 %cmp
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}
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define <2 x i1> @exact_lshr_ugt_false_vec(<2 x i32> %a) {
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; CHECK-LABEL: @exact_lshr_ugt_false_vec(
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; CHECK-NEXT: ret <2 x i1> zeroinitializer
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;
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%shr = lshr exact <2 x i32> <i32 30, i32 30>, %a
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%cmp = icmp ult <2 x i32> %shr, <i32 15, i32 15>
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ret <2 x i1> %cmp
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}
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; 'lshr C2, x' produces [C2 >> (Width-1), C2]
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define i1 @lshr_sgt_false(i32 %a) {
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; CHECK-LABEL: @lshr_sgt_false(
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; CHECK-NEXT: ret i1 false
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;
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%shr = lshr i32 1, %a
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%cmp = icmp sgt i32 %shr, 1
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ret i1 %cmp
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}
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define <2 x i1> @lshr_sgt_false_vec(<2 x i32> %a) {
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; CHECK-LABEL: @lshr_sgt_false_vec(
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; CHECK-NEXT: ret <2 x i1> zeroinitializer
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;
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%shr = lshr <2 x i32> <i32 1, i32 1>, %a
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%cmp = icmp sgt <2 x i32> %shr, <i32 1, i32 1>
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ret <2 x i1> %cmp
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}
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; 'ashr x, C2' produces [INT_MIN >> C2, INT_MAX >> C2]
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define i1 @ashr2(i32 %x) {
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; CHECK-LABEL: @ashr2(
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; CHECK-NEXT: ret i1 false
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;
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%s = ashr i32 %x, 30
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%c = icmp slt i32 %s, -5
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ret i1 %c
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}
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define <2 x i1> @ashr2_vec(<2 x i32> %x) {
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; CHECK-LABEL: @ashr2_vec(
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; CHECK-NEXT: ret <2 x i1> zeroinitializer
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;
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%s = ashr <2 x i32> %x, <i32 30, i32 30>
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%c = icmp slt <2 x i32> %s, <i32 -5, i32 -5>
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ret <2 x i1> %c
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}
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; 'ashr C2, x' produces [C2, C2 >> (Width-1)]
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define i1 @ashr_sgt_false(i32 %a) {
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; CHECK-LABEL: @ashr_sgt_false(
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; CHECK-NEXT: ret i1 false
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;
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%shr = ashr i32 -30, %a
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%cmp = icmp sgt i32 %shr, -1
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ret i1 %cmp
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}
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define <2 x i1> @ashr_sgt_false_vec(<2 x i32> %a) {
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; CHECK-LABEL: @ashr_sgt_false_vec(
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; CHECK-NEXT: ret <2 x i1> zeroinitializer
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;
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%shr = ashr <2 x i32> <i32 -30, i32 -30>, %a
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%cmp = icmp sgt <2 x i32> %shr, <i32 -1, i32 -1>
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ret <2 x i1> %cmp
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}
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; 'ashr C2, x' produces [C2, C2 >> (Width-1)]
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define i1 @exact_ashr_sgt_false(i32 %a) {
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; CHECK-LABEL: @exact_ashr_sgt_false(
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; CHECK-NEXT: ret i1 false
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;
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%shr = ashr exact i32 -30, %a
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%cmp = icmp sgt i32 %shr, -15
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ret i1 %cmp
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}
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define <2 x i1> @exact_ashr_sgt_false_vec(<2 x i32> %a) {
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; CHECK-LABEL: @exact_ashr_sgt_false_vec(
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; CHECK-NEXT: ret <2 x i1> zeroinitializer
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;
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%shr = ashr exact <2 x i32> <i32 -30, i32 -30>, %a
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%cmp = icmp sgt <2 x i32> %shr, <i32 -15, i32 -15>
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ret <2 x i1> %cmp
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}
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; 'or x, C2' produces [C2, UINT_MAX]
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define i1 @or1(i32 %X) {
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; CHECK-LABEL: @or1(
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; CHECK-NEXT: ret i1 false
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;
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%A = or i32 %X, 62
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%B = icmp ult i32 %A, 50
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ret i1 %B
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}
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define <2 x i1> @or1_vec(<2 x i32> %X) {
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; CHECK-LABEL: @or1_vec(
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; CHECK-NEXT: ret <2 x i1> zeroinitializer
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;
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%A = or <2 x i32> %X, <i32 62, i32 62>
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%B = icmp ult <2 x i32> %A, <i32 50, i32 50>
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ret <2 x i1> %B
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}
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; 'and x, C2' produces [0, C2]
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define i1 @and1(i32 %X) {
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; CHECK-LABEL: @and1(
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; CHECK-NEXT: ret i1 false
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;
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%A = and i32 %X, 62
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%B = icmp ugt i32 %A, 70
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ret i1 %B
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}
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define <2 x i1> @and1_vec(<2 x i32> %X) {
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; CHECK-LABEL: @and1_vec(
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; CHECK-NEXT: ret <2 x i1> zeroinitializer
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;
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%A = and <2 x i32> %X, <i32 62, i32 62>
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%B = icmp ugt <2 x i32> %A, <i32 70, i32 70>
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ret <2 x i1> %B
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}
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; 'add nuw x, C2' produces [C2, UINT_MAX]
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define i1 @tautological9(i32 %x) {
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; CHECK-LABEL: @tautological9(
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; CHECK-NEXT: ret i1 true
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;
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%add = add nuw i32 %x, 13
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%cmp = icmp ne i32 %add, 12
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ret i1 %cmp
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}
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define <2 x i1> @tautological9_vec(<2 x i32> %x) {
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; CHECK-LABEL: @tautological9_vec(
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; CHECK-NEXT: ret <2 x i1> <i1 true, i1 true>
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;
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%add = add nuw <2 x i32> %x, <i32 13, i32 13>
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%cmp = icmp ne <2 x i32> %add, <i32 12, i32 12>
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ret <2 x i1> %cmp
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}
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; The upper bound of the 'add' is 0.
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define i1 @add_nsw_neg_const1(i32 %x) {
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; CHECK-LABEL: @add_nsw_neg_const1(
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; CHECK-NEXT: ret i1 false
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;
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%add = add nsw i32 %x, -2147483647
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%cmp = icmp sgt i32 %add, 0
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ret i1 %cmp
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}
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; InstCombine can fold this, but not InstSimplify.
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define i1 @add_nsw_neg_const2(i32 %x) {
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; CHECK-LABEL: @add_nsw_neg_const2(
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; CHECK-NEXT: [[ADD:%.*]] = add nsw i32 %x, -2147483647
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; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i32 [[ADD]], -1
|
|
; CHECK-NEXT: ret i1 [[CMP]]
|
|
;
|
|
%add = add nsw i32 %x, -2147483647
|
|
%cmp = icmp sgt i32 %add, -1
|
|
ret i1 %cmp
|
|
}
|
|
|
|
; The upper bound of the 'add' is 1 (move the constants to prove we're doing range-based analysis).
|
|
|
|
define i1 @add_nsw_neg_const3(i32 %x) {
|
|
; CHECK-LABEL: @add_nsw_neg_const3(
|
|
; CHECK-NEXT: ret i1 false
|
|
;
|
|
%add = add nsw i32 %x, -2147483646
|
|
%cmp = icmp sgt i32 %add, 1
|
|
ret i1 %cmp
|
|
}
|
|
|
|
; InstCombine can fold this, but not InstSimplify.
|
|
|
|
define i1 @add_nsw_neg_const4(i32 %x) {
|
|
; CHECK-LABEL: @add_nsw_neg_const4(
|
|
; CHECK-NEXT: [[ADD:%.*]] = add nsw i32 %x, -2147483646
|
|
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i32 [[ADD]], 0
|
|
; CHECK-NEXT: ret i1 [[CMP]]
|
|
;
|
|
%add = add nsw i32 %x, -2147483646
|
|
%cmp = icmp sgt i32 %add, 0
|
|
ret i1 %cmp
|
|
}
|
|
|
|
; The upper bound of the 'add' is 2147483647 - 42 = 2147483605 (move the constants again and try a different cmp predicate).
|
|
|
|
define i1 @add_nsw_neg_const5(i32 %x) {
|
|
; CHECK-LABEL: @add_nsw_neg_const5(
|
|
; CHECK-NEXT: ret i1 true
|
|
;
|
|
%add = add nsw i32 %x, -42
|
|
%cmp = icmp ne i32 %add, 2147483606
|
|
ret i1 %cmp
|
|
}
|
|
|
|
; InstCombine can fold this, but not InstSimplify.
|
|
|
|
define i1 @add_nsw_neg_const6(i32 %x) {
|
|
; CHECK-LABEL: @add_nsw_neg_const6(
|
|
; CHECK-NEXT: [[ADD:%.*]] = add nsw i32 %x, -42
|
|
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i32 [[ADD]], 2147483605
|
|
; CHECK-NEXT: ret i1 [[CMP]]
|
|
;
|
|
%add = add nsw i32 %x, -42
|
|
%cmp = icmp ne i32 %add, 2147483605
|
|
ret i1 %cmp
|
|
}
|
|
|
|
; The lower bound of the 'add' is -1.
|
|
|
|
define i1 @add_nsw_pos_const1(i32 %x) {
|
|
; CHECK-LABEL: @add_nsw_pos_const1(
|
|
; CHECK-NEXT: ret i1 false
|
|
;
|
|
%add = add nsw i32 %x, 2147483647
|
|
%cmp = icmp slt i32 %add, -1
|
|
ret i1 %cmp
|
|
}
|
|
|
|
; InstCombine can fold this, but not InstSimplify.
|
|
|
|
define i1 @add_nsw_pos_const2(i32 %x) {
|
|
; CHECK-LABEL: @add_nsw_pos_const2(
|
|
; CHECK-NEXT: [[ADD:%.*]] = add nsw i32 %x, 2147483647
|
|
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[ADD]], 0
|
|
; CHECK-NEXT: ret i1 [[CMP]]
|
|
;
|
|
%add = add nsw i32 %x, 2147483647
|
|
%cmp = icmp slt i32 %add, 0
|
|
ret i1 %cmp
|
|
}
|
|
|
|
; The lower bound of the 'add' is -2 (move the constants to prove we're doing range-based analysis).
|
|
|
|
define i1 @add_nsw_pos_const3(i32 %x) {
|
|
; CHECK-LABEL: @add_nsw_pos_const3(
|
|
; CHECK-NEXT: ret i1 false
|
|
;
|
|
%add = add nsw i32 %x, 2147483646
|
|
%cmp = icmp slt i32 %add, -2
|
|
ret i1 %cmp
|
|
}
|
|
|
|
; InstCombine can fold this, but not InstSimplify.
|
|
|
|
define i1 @add_nsw_pos_const4(i32 %x) {
|
|
; CHECK-LABEL: @add_nsw_pos_const4(
|
|
; CHECK-NEXT: [[ADD:%.*]] = add nsw i32 %x, 2147483646
|
|
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[ADD]], -1
|
|
; CHECK-NEXT: ret i1 [[CMP]]
|
|
;
|
|
%add = add nsw i32 %x, 2147483646
|
|
%cmp = icmp slt i32 %add, -1
|
|
ret i1 %cmp
|
|
}
|
|
|
|
; The lower bound of the 'add' is -2147483648 + 42 = -2147483606 (move the constants again and change the cmp predicate).
|
|
|
|
define i1 @add_nsw_pos_const5(i32 %x) {
|
|
; CHECK-LABEL: @add_nsw_pos_const5(
|
|
; CHECK-NEXT: ret i1 false
|
|
;
|
|
%add = add nsw i32 %x, 42
|
|
%cmp = icmp eq i32 %add, -2147483607
|
|
ret i1 %cmp
|
|
}
|
|
|
|
; InstCombine can fold this, but not InstSimplify.
|
|
|
|
define i1 @add_nsw_pos_const6(i32 %x) {
|
|
; CHECK-LABEL: @add_nsw_pos_const6(
|
|
; CHECK-NEXT: [[ADD:%.*]] = add nsw i32 %x, 42
|
|
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[ADD]], -2147483606
|
|
; CHECK-NEXT: ret i1 [[CMP]]
|
|
;
|
|
%add = add nsw i32 %x, 42
|
|
%cmp = icmp eq i32 %add, -2147483606
|
|
ret i1 %cmp
|
|
}
|
|
|
|
; Verify that vectors work too.
|
|
|
|
define <2 x i1> @add_nsw_pos_const5_splat_vec(<2 x i32> %x) {
|
|
; CHECK-LABEL: @add_nsw_pos_const5_splat_vec(
|
|
; CHECK-NEXT: ret <2 x i1> <i1 true, i1 true>
|
|
;
|
|
%add = add nsw <2 x i32> %x, <i32 42, i32 42>
|
|
%cmp = icmp ne <2 x i32> %add, <i32 -2147483607, i32 -2147483607>
|
|
ret <2 x i1> %cmp
|
|
}
|
|
|
|
; PR34838 - https://bugs.llvm.org/show_bug.cgi?id=34838
|
|
; The shift is known to create poison, so we can simplify the cmp.
|
|
|
|
define i1 @ne_shl_by_constant_produces_poison(i8 %x) {
|
|
; CHECK-LABEL: @ne_shl_by_constant_produces_poison(
|
|
; CHECK-NEXT: ret i1 true
|
|
;
|
|
%zx = zext i8 %x to i16 ; zx = 0x00xx
|
|
%xor = xor i16 %zx, 32767 ; xor = 0x7fyy
|
|
%sub = sub nsw i16 %zx, %xor ; sub = 0x80zz (the top bit is known one)
|
|
%poison = shl nsw i16 %sub, 2 ; oops! this shl can't be nsw; that's POISON
|
|
%cmp = icmp ne i16 %poison, 1
|
|
ret i1 %cmp
|
|
}
|
|
|
|
define i1 @eq_shl_by_constant_produces_poison(i8 %x) {
|
|
; CHECK-LABEL: @eq_shl_by_constant_produces_poison(
|
|
; CHECK-NEXT: ret i1 false
|
|
;
|
|
%clear_high_bit = and i8 %x, 127 ; 0x7f
|
|
%set_next_high_bits = or i8 %clear_high_bit, 112 ; 0x70
|
|
%poison = shl nsw i8 %set_next_high_bits, 3
|
|
%cmp = icmp eq i8 %poison, 15
|
|
ret i1 %cmp
|
|
}
|
|
|
|
; Shift-by-variable that produces poison is more complicated but still possible.
|
|
; We guarantee that the shift will change the sign of the shifted value (and
|
|
; therefore produce poison) by limiting its range from 1 to 3.
|
|
|
|
define i1 @eq_shl_by_variable_produces_poison(i8 %x) {
|
|
; CHECK-LABEL: @eq_shl_by_variable_produces_poison(
|
|
; CHECK-NEXT: ret i1 false
|
|
;
|
|
%clear_high_bit = and i8 %x, 127 ; 0x7f
|
|
%set_next_high_bits = or i8 %clear_high_bit, 112 ; 0x70
|
|
%notundef_shiftamt = and i8 %x, 3
|
|
%nonzero_shiftamt = or i8 %notundef_shiftamt, 1
|
|
%poison = shl nsw i8 %set_next_high_bits, %nonzero_shiftamt
|
|
%cmp = icmp eq i8 %poison, 15
|
|
ret i1 %cmp
|
|
}
|
|
|