[InstCombine] foldICmpWithLowBitMaskedVal(): handle uncanonical ((1 << y)+(-1)) mask

Summary:
Same as to D52146.
`((1 << y)+(-1))` is simply non-canoniacal version of `~(-1 << y)`: https://rise4fun.com/Alive/0vl
We can not canonicalize it due to the extra uses. But we can handle it here.

Reviewers: spatel, craig.topper, RKSimon

Reviewed By: spatel

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D52147

llvm-svn: 342547

3 files changed, 65 insertions, 80 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index f06a0e83c9b..c6294d173d9 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -2887,6 +2887,7 @@ Instruction *InstCombiner::foldICmpInstWithConstantNotInt(ICmpInst &I) {
 /// Where Mask is some pattern that produces all-ones in low bits:
 ///    (-1 >> y)
 ///   ~(-1 << y)
+///    ((1 << y) + (-1))    <- non-canonical, has extra uses
 /// The Mask can be a constant, too.
 /// For some predicates, the operands are commutative.
 /// For others, x can only be on a specific side.
@@ -2894,8 +2895,10 @@ static Value *foldICmpWithLowBitMaskedVal(ICmpInst &I,
                                           InstCombiner::BuilderTy &Builder) {
   ICmpInst::Predicate SrcPred;
   Value *X, *M;
-  auto m_VariableMask = m_CombineOr(m_Not(m_Shl(m_AllOnes(), m_Value())),
-                                    m_LShr(m_AllOnes(), m_Value()));
+  auto m_VariableMask =
+      m_CombineOr(m_CombineOr(m_Not(m_Shl(m_AllOnes(), m_Value())),
+                              m_Add(m_Shl(m_One(), m_Value()), m_AllOnes())),
+                  m_LShr(m_AllOnes(), m_Value()));
   auto m_Mask = m_CombineOr(m_VariableMask, m_LowBitMask());
   if (!match(&I, m_c_ICmp(SrcPred,
                           m_c_And(m_CombineAnd(m_Mask, m_Value(M)), m_Value(X)),
diff --git a/llvm/test/Transforms/InstCombine/canonicalize-low-bit-mask-v3-and-icmp-eq-to-icmp-ule.ll b/llvm/test/Transforms/InstCombine/canonicalize-low-bit-mask-v3-and-icmp-eq-to-icmp-ule.ll
index 9604a5c5794..af7700c8473 100644
--- a/llvm/test/Transforms/InstCombine/canonicalize-low-bit-mask-v3-and-icmp-eq-to-icmp-ule.ll
+++ b/llvm/test/Transforms/InstCombine/canonicalize-low-bit-mask-v3-and-icmp-eq-to-icmp-ule.ll
@@ -24,10 +24,9 @@ define i1 @p0(i8 %x, i8 %y) {
 ; CHECK-LABEL: @p0(
 ; CHECK-NEXT:    [[T0:%.*]] = shl i8 1, [[Y:%.*]]
 ; CHECK-NEXT:    call void @use8(i8 [[T0]])
-; CHECK-NEXT:    [[T1:%.*]] = add i8 [[T0]], -1
-; CHECK-NEXT:    [[T2:%.*]] = and i8 [[T1]], [[X:%.*]]
-; CHECK-NEXT:    [[RET:%.*]] = icmp eq i8 [[T2]], [[X]]
-; CHECK-NEXT:    ret i1 [[RET]]
+; CHECK-NEXT:    [[X_HIGHBITS:%.*]] = lshr i8 [[X:%.*]], [[Y]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq i8 [[X_HIGHBITS]], 0
+; CHECK-NEXT:    ret i1 [[TMP1]]
 ;
   %t0 = shl i8 1, %y
   call void @use8(i8 %t0)
@@ -45,10 +44,9 @@ define <2 x i1> @p1_vec(<2 x i8> %x, <2 x i8> %y) {
 ; CHECK-LABEL: @p1_vec(
 ; CHECK-NEXT:    [[T0:%.*]] = shl <2 x i8> <i8 1, i8 1>, [[Y:%.*]]
 ; CHECK-NEXT:    call void @use2i8(<2 x i8> [[T0]])
-; CHECK-NEXT:    [[T1:%.*]] = add <2 x i8> [[T0]], <i8 -1, i8 -1>
-; CHECK-NEXT:    [[T2:%.*]] = and <2 x i8> [[T1]], [[X:%.*]]
-; CHECK-NEXT:    [[RET:%.*]] = icmp eq <2 x i8> [[T2]], [[X]]
-; CHECK-NEXT:    ret <2 x i1> [[RET]]
+; CHECK-NEXT:    [[X_HIGHBITS:%.*]] = lshr <2 x i8> [[X:%.*]], [[Y]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq <2 x i8> [[X_HIGHBITS]], zeroinitializer
+; CHECK-NEXT:    ret <2 x i1> [[TMP1]]
 ;
   %t0 = shl <2 x i8> <i8 1, i8 1>, %y
   call void @use2i8(<2 x i8> %t0)
@@ -62,10 +60,9 @@ define <3 x i1> @p2_vec_undef0(<3 x i8> %x, <3 x i8> %y) {
 ; CHECK-LABEL: @p2_vec_undef0(
 ; CHECK-NEXT:    [[T0:%.*]] = shl <3 x i8> <i8 1, i8 undef, i8 1>, [[Y:%.*]]
 ; CHECK-NEXT:    call void @use3i8(<3 x i8> [[T0]])
-; CHECK-NEXT:    [[T1:%.*]] = add <3 x i8> [[T0]], <i8 -1, i8 -1, i8 -1>
-; CHECK-NEXT:    [[T2:%.*]] = and <3 x i8> [[T1]], [[X:%.*]]
-; CHECK-NEXT:    [[RET:%.*]] = icmp eq <3 x i8> [[T2]], [[X]]
-; CHECK-NEXT:    ret <3 x i1> [[RET]]
+; CHECK-NEXT:    [[X_HIGHBITS:%.*]] = lshr <3 x i8> [[X:%.*]], [[Y]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq <3 x i8> [[X_HIGHBITS]], zeroinitializer
+; CHECK-NEXT:    ret <3 x i1> [[TMP1]]
 ;
   %t0 = shl <3 x i8> <i8 1, i8 undef, i8 1>, %y
   call void @use3i8(<3 x i8> %t0)
@@ -79,10 +76,9 @@ define <3 x i1> @p3_vec_undef0(<3 x i8> %x, <3 x i8> %y) {
 ; CHECK-LABEL: @p3_vec_undef0(
 ; CHECK-NEXT:    [[T0:%.*]] = shl <3 x i8> <i8 1, i8 1, i8 1>, [[Y:%.*]]
 ; CHECK-NEXT:    call void @use3i8(<3 x i8> [[T0]])
-; CHECK-NEXT:    [[T1:%.*]] = add <3 x i8> [[T0]], <i8 -1, i8 undef, i8 -1>
-; CHECK-NEXT:    [[T2:%.*]] = and <3 x i8> [[T1]], [[X:%.*]]
-; CHECK-NEXT:    [[RET:%.*]] = icmp eq <3 x i8> [[T2]], [[X]]
-; CHECK-NEXT:    ret <3 x i1> [[RET]]
+; CHECK-NEXT:    [[X_HIGHBITS:%.*]] = lshr <3 x i8> [[X:%.*]], [[Y]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq <3 x i8> [[X_HIGHBITS]], zeroinitializer
+; CHECK-NEXT:    ret <3 x i1> [[TMP1]]
 ;
   %t0 = shl <3 x i8> <i8 1, i8 1, i8 1>, %y
   call void @use3i8(<3 x i8> %t0)
@@ -96,10 +92,9 @@ define <3 x i1> @p4_vec_undef2(<3 x i8> %x, <3 x i8> %y) {
 ; CHECK-LABEL: @p4_vec_undef2(
 ; CHECK-NEXT:    [[T0:%.*]] = shl <3 x i8> <i8 1, i8 undef, i8 1>, [[Y:%.*]]
 ; CHECK-NEXT:    call void @use3i8(<3 x i8> [[T0]])
-; CHECK-NEXT:    [[T1:%.*]] = add <3 x i8> [[T0]], <i8 -1, i8 undef, i8 -1>
-; CHECK-NEXT:    [[T2:%.*]] = and <3 x i8> [[T1]], [[X:%.*]]
-; CHECK-NEXT:    [[RET:%.*]] = icmp eq <3 x i8> [[T2]], [[X]]
-; CHECK-NEXT:    ret <3 x i1> [[RET]]
+; CHECK-NEXT:    [[X_HIGHBITS:%.*]] = lshr <3 x i8> [[X:%.*]], [[Y]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq <3 x i8> [[X_HIGHBITS]], zeroinitializer
+; CHECK-NEXT:    ret <3 x i1> [[TMP1]]
 ;
   %t0 = shl <3 x i8> <i8 1, i8 undef, i8 1>, %y
   call void @use3i8(<3 x i8> %t0)
@@ -119,11 +114,10 @@ define i1 @c0(i8 %y) {
 ; CHECK-LABEL: @c0(
 ; CHECK-NEXT:    [[T0:%.*]] = shl i8 1, [[Y:%.*]]
 ; CHECK-NEXT:    call void @use8(i8 [[T0]])
-; CHECK-NEXT:    [[T1:%.*]] = add i8 [[T0]], -1
 ; CHECK-NEXT:    [[X:%.*]] = call i8 @gen8()
-; CHECK-NEXT:    [[T2:%.*]] = and i8 [[X]], [[T1]]
-; CHECK-NEXT:    [[RET:%.*]] = icmp eq i8 [[T2]], [[X]]
-; CHECK-NEXT:    ret i1 [[RET]]
+; CHECK-NEXT:    [[X_HIGHBITS:%.*]] = lshr i8 [[X]], [[Y]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq i8 [[X_HIGHBITS]], 0
+; CHECK-NEXT:    ret i1 [[TMP1]]
 ;
   %t0 = shl i8 1, %y
   call void @use8(i8 %t0)
@@ -138,11 +132,10 @@ define i1 @c1(i8 %y) {
 ; CHECK-LABEL: @c1(
 ; CHECK-NEXT:    [[T0:%.*]] = shl i8 1, [[Y:%.*]]
 ; CHECK-NEXT:    call void @use8(i8 [[T0]])
-; CHECK-NEXT:    [[T1:%.*]] = add i8 [[T0]], -1
 ; CHECK-NEXT:    [[X:%.*]] = call i8 @gen8()
-; CHECK-NEXT:    [[T2:%.*]] = and i8 [[T1]], [[X]]
-; CHECK-NEXT:    [[RET:%.*]] = icmp eq i8 [[X]], [[T2]]
-; CHECK-NEXT:    ret i1 [[RET]]
+; CHECK-NEXT:    [[X_HIGHBITS:%.*]] = lshr i8 [[X]], [[Y]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq i8 [[X_HIGHBITS]], 0
+; CHECK-NEXT:    ret i1 [[TMP1]]
 ;
   %t0 = shl i8 1, %y
   call void @use8(i8 %t0)
@@ -157,11 +150,10 @@ define i1 @c2(i8 %y) {
 ; CHECK-LABEL: @c2(
 ; CHECK-NEXT:    [[T0:%.*]] = shl i8 1, [[Y:%.*]]
 ; CHECK-NEXT:    call void @use8(i8 [[T0]])
-; CHECK-NEXT:    [[T1:%.*]] = add i8 [[T0]], -1
 ; CHECK-NEXT:    [[X:%.*]] = call i8 @gen8()
-; CHECK-NEXT:    [[T2:%.*]] = and i8 [[X]], [[T1]]
-; CHECK-NEXT:    [[RET:%.*]] = icmp eq i8 [[X]], [[T2]]
-; CHECK-NEXT:    ret i1 [[RET]]
+; CHECK-NEXT:    [[X_HIGHBITS:%.*]] = lshr i8 [[X]], [[Y]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq i8 [[X_HIGHBITS]], 0
+; CHECK-NEXT:    ret i1 [[TMP1]]
 ;
   %t0 = shl i8 1, %y
   call void @use8(i8 %t0)
@@ -182,9 +174,8 @@ define i1 @oneuse0(i8 %x, i8 %y) {
 ; CHECK-NEXT:    call void @use8(i8 [[T0]])
 ; CHECK-NEXT:    [[T1:%.*]] = add i8 [[T0]], -1
 ; CHECK-NEXT:    call void @use8(i8 [[T1]])
-; CHECK-NEXT:    [[T2:%.*]] = and i8 [[T1]], [[X:%.*]]
-; CHECK-NEXT:    [[RET:%.*]] = icmp eq i8 [[T2]], [[X]]
-; CHECK-NEXT:    ret i1 [[RET]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp uge i8 [[T1]], [[X:%.*]]
+; CHECK-NEXT:    ret i1 [[TMP1]]
 ;
   %t0 = shl i8 1, %y
   call void @use8(i8 %t0) ; needed anyway
@@ -202,8 +193,8 @@ define i1 @oneuse1(i8 %x, i8 %y) {
 ; CHECK-NEXT:    [[T1:%.*]] = add i8 [[T0]], -1
 ; CHECK-NEXT:    [[T2:%.*]] = and i8 [[T1]], [[X:%.*]]
 ; CHECK-NEXT:    call void @use8(i8 [[T2]])
-; CHECK-NEXT:    [[RET:%.*]] = icmp eq i8 [[T2]], [[X]]
-; CHECK-NEXT:    ret i1 [[RET]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp uge i8 [[T1]], [[X]]
+; CHECK-NEXT:    ret i1 [[TMP1]]
 ;
   %t0 = shl i8 1, %y
   call void @use8(i8 %t0) ; needed anyway
@@ -222,8 +213,8 @@ define i1 @oneuse2(i8 %x, i8 %y) {
 ; CHECK-NEXT:    call void @use8(i8 [[T1]])
 ; CHECK-NEXT:    [[T2:%.*]] = and i8 [[T1]], [[X:%.*]]
 ; CHECK-NEXT:    call void @use8(i8 [[T2]])
-; CHECK-NEXT:    [[RET:%.*]] = icmp eq i8 [[T2]], [[X]]
-; CHECK-NEXT:    ret i1 [[RET]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp uge i8 [[T1]], [[X]]
+; CHECK-NEXT:    ret i1 [[TMP1]]
 ;
   %t0 = shl i8 1, %y
   call void @use8(i8 %t0)
diff --git a/llvm/test/Transforms/InstCombine/canonicalize-low-bit-mask-v3-and-icmp-ne-to-icmp-ugt.ll b/llvm/test/Transforms/InstCombine/canonicalize-low-bit-mask-v3-and-icmp-ne-to-icmp-ugt.ll
index fd68e2b896b..dfe5b713284 100644
--- a/llvm/test/Transforms/InstCombine/canonicalize-low-bit-mask-v3-and-icmp-ne-to-icmp-ugt.ll
+++ b/llvm/test/Transforms/InstCombine/canonicalize-low-bit-mask-v3-and-icmp-ne-to-icmp-ugt.ll
@@ -24,10 +24,9 @@ define i1 @p0(i8 %x, i8 %y) {
 ; CHECK-LABEL: @p0(
 ; CHECK-NEXT:    [[T0:%.*]] = shl i8 1, [[Y:%.*]]
 ; CHECK-NEXT:    call void @use8(i8 [[T0]])
-; CHECK-NEXT:    [[T1:%.*]] = add i8 [[T0]], -1
-; CHECK-NEXT:    [[T2:%.*]] = and i8 [[T1]], [[X:%.*]]
-; CHECK-NEXT:    [[RET:%.*]] = icmp ne i8 [[T2]], [[X]]
-; CHECK-NEXT:    ret i1 [[RET]]
+; CHECK-NEXT:    [[X_HIGHBITS:%.*]] = lshr i8 [[X:%.*]], [[Y]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ne i8 [[X_HIGHBITS]], 0
+; CHECK-NEXT:    ret i1 [[TMP1]]
 ;
   %t0 = shl i8 1, %y
   call void @use8(i8 %t0)
@@ -45,10 +44,9 @@ define <2 x i1> @p1_vec(<2 x i8> %x, <2 x i8> %y) {
 ; CHECK-LABEL: @p1_vec(
 ; CHECK-NEXT:    [[T0:%.*]] = shl <2 x i8> <i8 1, i8 1>, [[Y:%.*]]
 ; CHECK-NEXT:    call void @use2i8(<2 x i8> [[T0]])
-; CHECK-NEXT:    [[T1:%.*]] = add <2 x i8> [[T0]], <i8 -1, i8 -1>
-; CHECK-NEXT:    [[T2:%.*]] = and <2 x i8> [[T1]], [[X:%.*]]
-; CHECK-NEXT:    [[RET:%.*]] = icmp ne <2 x i8> [[T2]], [[X]]
-; CHECK-NEXT:    ret <2 x i1> [[RET]]
+; CHECK-NEXT:    [[X_HIGHBITS:%.*]] = lshr <2 x i8> [[X:%.*]], [[Y]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ne <2 x i8> [[X_HIGHBITS]], zeroinitializer
+; CHECK-NEXT:    ret <2 x i1> [[TMP1]]
 ;
   %t0 = shl <2 x i8> <i8 1, i8 1>, %y
   call void @use2i8(<2 x i8> %t0)
@@ -62,10 +60,9 @@ define <3 x i1> @p2_vec_undef0(<3 x i8> %x, <3 x i8> %y) {
 ; CHECK-LABEL: @p2_vec_undef0(
 ; CHECK-NEXT:    [[T0:%.*]] = shl <3 x i8> <i8 1, i8 undef, i8 1>, [[Y:%.*]]
 ; CHECK-NEXT:    call void @use3i8(<3 x i8> [[T0]])
-; CHECK-NEXT:    [[T1:%.*]] = add <3 x i8> [[T0]], <i8 -1, i8 -1, i8 -1>
-; CHECK-NEXT:    [[T2:%.*]] = and <3 x i8> [[T1]], [[X:%.*]]
-; CHECK-NEXT:    [[RET:%.*]] = icmp ne <3 x i8> [[T2]], [[X]]
-; CHECK-NEXT:    ret <3 x i1> [[RET]]
+; CHECK-NEXT:    [[X_HIGHBITS:%.*]] = lshr <3 x i8> [[X:%.*]], [[Y]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ne <3 x i8> [[X_HIGHBITS]], zeroinitializer
+; CHECK-NEXT:    ret <3 x i1> [[TMP1]]
 ;
   %t0 = shl <3 x i8> <i8 1, i8 undef, i8 1>, %y
   call void @use3i8(<3 x i8> %t0)
@@ -79,10 +76,9 @@ define <3 x i1> @p3_vec_undef0(<3 x i8> %x, <3 x i8> %y) {
 ; CHECK-LABEL: @p3_vec_undef0(
 ; CHECK-NEXT:    [[T0:%.*]] = shl <3 x i8> <i8 1, i8 1, i8 1>, [[Y:%.*]]
 ; CHECK-NEXT:    call void @use3i8(<3 x i8> [[T0]])
-; CHECK-NEXT:    [[T1:%.*]] = add <3 x i8> [[T0]], <i8 -1, i8 undef, i8 -1>
-; CHECK-NEXT:    [[T2:%.*]] = and <3 x i8> [[T1]], [[X:%.*]]
-; CHECK-NEXT:    [[RET:%.*]] = icmp ne <3 x i8> [[T2]], [[X]]
-; CHECK-NEXT:    ret <3 x i1> [[RET]]
+; CHECK-NEXT:    [[X_HIGHBITS:%.*]] = lshr <3 x i8> [[X:%.*]], [[Y]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ne <3 x i8> [[X_HIGHBITS]], zeroinitializer
+; CHECK-NEXT:    ret <3 x i1> [[TMP1]]
 ;
   %t0 = shl <3 x i8> <i8 1, i8 1, i8 1>, %y
   call void @use3i8(<3 x i8> %t0)
@@ -96,10 +92,9 @@ define <3 x i1> @p4_vec_undef2(<3 x i8> %x, <3 x i8> %y) {
 ; CHECK-LABEL: @p4_vec_undef2(
 ; CHECK-NEXT:    [[T0:%.*]] = shl <3 x i8> <i8 1, i8 undef, i8 1>, [[Y:%.*]]
 ; CHECK-NEXT:    call void @use3i8(<3 x i8> [[T0]])
-; CHECK-NEXT:    [[T1:%.*]] = add <3 x i8> [[T0]], <i8 -1, i8 undef, i8 -1>
-; CHECK-NEXT:    [[T2:%.*]] = and <3 x i8> [[T1]], [[X:%.*]]
-; CHECK-NEXT:    [[RET:%.*]] = icmp ne <3 x i8> [[T2]], [[X]]
-; CHECK-NEXT:    ret <3 x i1> [[RET]]
+; CHECK-NEXT:    [[X_HIGHBITS:%.*]] = lshr <3 x i8> [[X:%.*]], [[Y]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ne <3 x i8> [[X_HIGHBITS]], zeroinitializer
+; CHECK-NEXT:    ret <3 x i1> [[TMP1]]
 ;
   %t0 = shl <3 x i8> <i8 1, i8 undef, i8 1>, %y
   call void @use3i8(<3 x i8> %t0)
@@ -119,11 +114,10 @@ define i1 @c0(i8 %y) {
 ; CHECK-LABEL: @c0(
 ; CHECK-NEXT:    [[T0:%.*]] = shl i8 1, [[Y:%.*]]
 ; CHECK-NEXT:    call void @use8(i8 [[T0]])
-; CHECK-NEXT:    [[T1:%.*]] = add i8 [[T0]], -1
 ; CHECK-NEXT:    [[X:%.*]] = call i8 @gen8()
-; CHECK-NEXT:    [[T2:%.*]] = and i8 [[X]], [[T1]]
-; CHECK-NEXT:    [[RET:%.*]] = icmp ne i8 [[T2]], [[X]]
-; CHECK-NEXT:    ret i1 [[RET]]
+; CHECK-NEXT:    [[X_HIGHBITS:%.*]] = lshr i8 [[X]], [[Y]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ne i8 [[X_HIGHBITS]], 0
+; CHECK-NEXT:    ret i1 [[TMP1]]
 ;
   %t0 = shl i8 1, %y
   call void @use8(i8 %t0)
@@ -138,11 +132,10 @@ define i1 @c1(i8 %y) {
 ; CHECK-LABEL: @c1(
 ; CHECK-NEXT:    [[T0:%.*]] = shl i8 1, [[Y:%.*]]
 ; CHECK-NEXT:    call void @use8(i8 [[T0]])
-; CHECK-NEXT:    [[T1:%.*]] = add i8 [[T0]], -1
 ; CHECK-NEXT:    [[X:%.*]] = call i8 @gen8()
-; CHECK-NEXT:    [[T2:%.*]] = and i8 [[T1]], [[X]]
-; CHECK-NEXT:    [[RET:%.*]] = icmp ne i8 [[X]], [[T2]]
-; CHECK-NEXT:    ret i1 [[RET]]
+; CHECK-NEXT:    [[X_HIGHBITS:%.*]] = lshr i8 [[X]], [[Y]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ne i8 [[X_HIGHBITS]], 0
+; CHECK-NEXT:    ret i1 [[TMP1]]
 ;
   %t0 = shl i8 1, %y
   call void @use8(i8 %t0)
@@ -157,11 +150,10 @@ define i1 @c2(i8 %y) {
 ; CHECK-LABEL: @c2(
 ; CHECK-NEXT:    [[T0:%.*]] = shl i8 1, [[Y:%.*]]
 ; CHECK-NEXT:    call void @use8(i8 [[T0]])
-; CHECK-NEXT:    [[T1:%.*]] = add i8 [[T0]], -1
 ; CHECK-NEXT:    [[X:%.*]] = call i8 @gen8()
-; CHECK-NEXT:    [[T2:%.*]] = and i8 [[X]], [[T1]]
-; CHECK-NEXT:    [[RET:%.*]] = icmp ne i8 [[X]], [[T2]]
-; CHECK-NEXT:    ret i1 [[RET]]
+; CHECK-NEXT:    [[X_HIGHBITS:%.*]] = lshr i8 [[X]], [[Y]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ne i8 [[X_HIGHBITS]], 0
+; CHECK-NEXT:    ret i1 [[TMP1]]
 ;
   %t0 = shl i8 1, %y
   call void @use8(i8 %t0)
@@ -182,9 +174,8 @@ define i1 @oneuse0(i8 %x, i8 %y) {
 ; CHECK-NEXT:    call void @use8(i8 [[T0]])
 ; CHECK-NEXT:    [[T1:%.*]] = add i8 [[T0]], -1
 ; CHECK-NEXT:    call void @use8(i8 [[T1]])
-; CHECK-NEXT:    [[T2:%.*]] = and i8 [[T1]], [[X:%.*]]
-; CHECK-NEXT:    [[RET:%.*]] = icmp ne i8 [[T2]], [[X]]
-; CHECK-NEXT:    ret i1 [[RET]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ult i8 [[T1]], [[X:%.*]]
+; CHECK-NEXT:    ret i1 [[TMP1]]
 ;
   %t0 = shl i8 1, %y
   call void @use8(i8 %t0) ; needed anyway
@@ -202,8 +193,8 @@ define i1 @oneuse1(i8 %x, i8 %y) {
 ; CHECK-NEXT:    [[T1:%.*]] = add i8 [[T0]], -1
 ; CHECK-NEXT:    [[T2:%.*]] = and i8 [[T1]], [[X:%.*]]
 ; CHECK-NEXT:    call void @use8(i8 [[T2]])
-; CHECK-NEXT:    [[RET:%.*]] = icmp ne i8 [[T2]], [[X]]
-; CHECK-NEXT:    ret i1 [[RET]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ult i8 [[T1]], [[X]]
+; CHECK-NEXT:    ret i1 [[TMP1]]
 ;
   %t0 = shl i8 1, %y
   call void @use8(i8 %t0) ; needed anyway
@@ -222,8 +213,8 @@ define i1 @oneuse2(i8 %x, i8 %y) {
 ; CHECK-NEXT:    call void @use8(i8 [[T1]])
 ; CHECK-NEXT:    [[T2:%.*]] = and i8 [[T1]], [[X:%.*]]
 ; CHECK-NEXT:    call void @use8(i8 [[T2]])
-; CHECK-NEXT:    [[RET:%.*]] = icmp ne i8 [[T2]], [[X]]
-; CHECK-NEXT:    ret i1 [[RET]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ult i8 [[T1]], [[X]]
+; CHECK-NEXT:    ret i1 [[TMP1]]
 ;
   %t0 = shl i8 1, %y
   call void @use8(i8 %t0)