[InstCombine] fold icmp of the sum of ext bool based on limited range

For the pattern `(zext i1 X) + (sext i1 Y)`, the constant range is [-1, 1]. We can simplify the pattern by logical operations. Like: ``` (zext i1 X) + (sext i1 Y) == -1 --> ~X & Y (zext i1 X) + (sext i1 Y) == 0 --> ~(X ^ Y) (zext i1 X) + (sext i1 Y) == 1 --> X & ~Y ``` And other predicates can the combination of these results: ``` (zext i1 X) + (sext i1 Y)) != -1 --> X | ~Y (zext i1 X) + (sext i1 Y)) s> -1 --> X | ~Y (zext i1 X) + (sext i1 Y)) u< -1 --> X | ~Y (zext i1 X) + (sext i1 Y)) s> 0 --> X & ~Y (zext i1 X) + (sext i1 Y)) s< 0 --> ~X & Y (zext i1 X) + (sext i1 Y)) != 1 --> ~X | Y (zext i1 X) + (sext i1 Y)) s< 1 --> ~X | Y (zext i1 X) + (sext i1 Y)) u> 1 --> ~X & Y ``` All alive proofs: https://alive2.llvm.org/ce/z/KmgDpF https://alive2.llvm.org/ce/z/fLwWa9 https://alive2.llvm.org/ce/z/ZKQn2P Fix: llvm/llvm-project#59666 Reviewed By: spatel Differential Revision: https://reviews.llvm.org/D143373
SNSystems · Feb 15, 2023 · 72edd8b · 72edd8b
1 parent 35d1d74
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diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -5863,8 +5863,7 @@ Instruction *InstCombinerImpl::foldICmpUsingKnownBits(ICmpInst &I) {
 
 /// If one operand of an icmp is effectively a bool (value range of {0,1}),
 /// then try to reduce patterns based on that limit.
-static Instruction *foldICmpUsingBoolRange(ICmpInst &I,
-                                           InstCombiner::BuilderTy &Builder) {
+Instruction *InstCombinerImpl::foldICmpUsingBoolRange(ICmpInst &I) {
   Value *X, *Y;
   ICmpInst::Predicate Pred;
 
@@ -5880,6 +5879,59 @@ static Instruction *foldICmpUsingBoolRange(ICmpInst &I,
       Y->getType()->isIntOrIntVectorTy(1) && Pred == ICmpInst::ICMP_ULE)
     return BinaryOperator::CreateOr(Builder.CreateIsNull(X), Y);
 
+  const APInt *C;
+  if (match(I.getOperand(0),
+            m_OneUse(m_c_Add(m_ZExt(m_Value(X)), m_SExt(m_Value(Y))))) &&
+      match(I.getOperand(1), m_APInt(C)) &&
+      X->getType()->isIntOrIntVectorTy(1) &&
+      Y->getType()->isIntOrIntVectorTy(1)) {
+    unsigned BitWidth = C->getBitWidth();
+    Pred = I.getPredicate();
+    APInt Zero = APInt::getZero(BitWidth);
+    APInt MinusOne = APInt::getAllOnes(BitWidth);
+    APInt One(BitWidth, 1);
+    if ((C->sgt(Zero) && Pred == ICmpInst::ICMP_SGT) ||
+        (C->slt(Zero) && Pred == ICmpInst::ICMP_SLT))
+      return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
+    if ((C->sgt(One) && Pred == ICmpInst::ICMP_SLT) ||
+        (C->slt(MinusOne) && Pred == ICmpInst::ICMP_SGT))
+      return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
+
+    APInt NewC = *C;
+    // canonicalize predicate to eq/ne
+    if ((*C == Zero && Pred == ICmpInst::ICMP_SLT) ||
+        (*C != Zero && *C != MinusOne && Pred == ICmpInst::ICMP_UGT)) {
+      // x s< 0 in [-1, 1] --> x == -1
+      // x u> 1(or any const !=0 !=-1) in [-1, 1] --> x == -1
+      NewC = MinusOne;
+      Pred = ICmpInst::ICMP_EQ;
+    } else if ((*C == MinusOne && Pred == ICmpInst::ICMP_SGT) ||
+               (*C != Zero && *C != One && Pred == ICmpInst::ICMP_ULT)) {
+      // x s> -1 in [-1, 1] --> x != -1
+      // x u< -1 in [-1, 1] --> x != -1
+      Pred = ICmpInst::ICMP_NE;
+    } else if (*C == Zero && Pred == ICmpInst::ICMP_SGT) {
+      // x s> 0 in [-1, 1] --> x == 1
+      NewC = One;
+      Pred = ICmpInst::ICMP_EQ;
+    } else if (*C == One && Pred == ICmpInst::ICMP_SLT) {
+      // x s< 1 in [-1, 1] --> x != 1
+      Pred = ICmpInst::ICMP_NE;
+    }
+
+    if (NewC == MinusOne) {
+      if (Pred == ICmpInst::ICMP_EQ)
+        return BinaryOperator::CreateAnd(Builder.CreateNot(X), Y);
+      if (Pred == ICmpInst::ICMP_NE)
+        return BinaryOperator::CreateOr(X, Builder.CreateNot(Y));
+    } else if (NewC == One) {
+      if (Pred == ICmpInst::ICMP_EQ)
+        return BinaryOperator::CreateAnd(X, Builder.CreateNot(Y));
+      if (Pred == ICmpInst::ICMP_NE)
+        return BinaryOperator::CreateOr(Builder.CreateNot(X), Y);
+    }
+  }
+
   return nullptr;
 }
 
@@ -6335,7 +6387,7 @@ Instruction *InstCombinerImpl::visitICmpInst(ICmpInst &I) {
   if (Instruction *Res = foldICmpWithDominatingICmp(I))
     return Res;
 
-  if (Instruction *Res = foldICmpUsingBoolRange(I, Builder))
+  if (Instruction *Res = foldICmpUsingBoolRange(I))
     return Res;
 
   if (Instruction *Res = foldICmpUsingKnownBits(I))

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -565,6 +565,7 @@ class LLVM_LIBRARY_VISIBILITY InstCombinerImpl final
   Instruction *foldICmpUsingKnownBits(ICmpInst &Cmp);
   Instruction *foldICmpWithDominatingICmp(ICmpInst &Cmp);
   Instruction *foldICmpWithConstant(ICmpInst &Cmp);
+  Instruction *foldICmpUsingBoolRange(ICmpInst &I);
   Instruction *foldICmpInstWithConstant(ICmpInst &Cmp);
   Instruction *foldICmpInstWithConstantNotInt(ICmpInst &Cmp);
   Instruction *foldICmpInstWithConstantAllowUndef(ICmpInst &Cmp,

diff --git a/llvm/test/Transforms/InstCombine/icmp-range.ll b/llvm/test/Transforms/InstCombine/icmp-range.ll
@@ -629,13 +629,11 @@ define i1 @ashr_uge_sub(i8 %b, i8 %x, i8 %y) {
   ret i1 %r
 }
 
+; (zext i1 a) + (sext i1 b)) s< -1 --> false
+
 define i1 @zext_sext_add_icmp_slt_minus1(i1 %a, i1 %b) {
 ; CHECK-LABEL: @zext_sext_add_icmp_slt_minus1(
-; CHECK-NEXT:    [[ZEXT_A:%.*]] = zext i1 [[A:%.*]] to i8
-; CHECK-NEXT:    [[SEXT_B:%.*]] = sext i1 [[B:%.*]] to i8
-; CHECK-NEXT:    [[ADD:%.*]] = add nsw i8 [[ZEXT_A]], [[SEXT_B]]
-; CHECK-NEXT:    [[R:%.*]] = icmp slt i8 [[ADD]], -1
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %zext.a = zext i1 %a to i8
   %sext.b = sext i1 %b to i8
@@ -644,13 +642,11 @@ define i1 @zext_sext_add_icmp_slt_minus1(i1 %a, i1 %b) {
   ret i1 %r
 }
 
+; (zext i1 a) + (sext i1 b)) s> 1 --> false
+
 define i1 @zext_sext_add_icmp_sgt_1(i1 %a, i1 %b) {
 ; CHECK-LABEL: @zext_sext_add_icmp_sgt_1(
-; CHECK-NEXT:    [[ZEXT_A:%.*]] = zext i1 [[A:%.*]] to i8
-; CHECK-NEXT:    [[SEXT_B:%.*]] = sext i1 [[B:%.*]] to i8
-; CHECK-NEXT:    [[ADD:%.*]] = add nsw i8 [[ZEXT_A]], [[SEXT_B]]
-; CHECK-NEXT:    [[R:%.*]] = icmp sgt i8 [[ADD]], 1
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %zext.a = zext i1 %a to i8
   %sext.b = sext i1 %b to i8
@@ -659,13 +655,11 @@ define i1 @zext_sext_add_icmp_sgt_1(i1 %a, i1 %b) {
   ret i1 %r
 }
 
+; (zext i1 a) + (sext i1 b)) s> -2 --> true
+
 define i1 @zext_sext_add_icmp_sgt_minus2(i1 %a, i1 %b) {
 ; CHECK-LABEL: @zext_sext_add_icmp_sgt_minus2(
-; CHECK-NEXT:    [[ZEXT_A:%.*]] = zext i1 [[A:%.*]] to i8
-; CHECK-NEXT:    [[SEXT_B:%.*]] = sext i1 [[B:%.*]] to i8
-; CHECK-NEXT:    [[ADD:%.*]] = add nsw i8 [[ZEXT_A]], [[SEXT_B]]
-; CHECK-NEXT:    [[R:%.*]] = icmp sgt i8 [[ADD]], -2
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 true
 ;
   %zext.a = zext i1 %a to i8
   %sext.b = sext i1 %b to i8
@@ -674,13 +668,11 @@ define i1 @zext_sext_add_icmp_sgt_minus2(i1 %a, i1 %b) {
   ret i1 %r
 }
 
+; (zext i1 a) + (sext i1 b)) s< 2 --> true
+
 define i1 @zext_sext_add_icmp_slt_2(i1 %a, i1 %b) {
 ; CHECK-LABEL: @zext_sext_add_icmp_slt_2(
-; CHECK-NEXT:    [[ZEXT_A:%.*]] = zext i1 [[A:%.*]] to i8
-; CHECK-NEXT:    [[SEXT_B:%.*]] = sext i1 [[B:%.*]] to i8
-; CHECK-NEXT:    [[ADD:%.*]] = add nsw i8 [[ZEXT_A]], [[SEXT_B]]
-; CHECK-NEXT:    [[R:%.*]] = icmp slt i8 [[ADD]], 2
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 true
 ;
   %zext.a = zext i1 %a to i8
   %sext.b = sext i1 %b to i8
@@ -689,13 +681,11 @@ define i1 @zext_sext_add_icmp_slt_2(i1 %a, i1 %b) {
   ret i1 %r
 }
 
+; test case with i128
+
 define i1 @zext_sext_add_icmp_i128(i1 %a, i1 %b) {
 ; CHECK-LABEL: @zext_sext_add_icmp_i128(
-; CHECK-NEXT:    [[ZEXT_A:%.*]] = zext i1 [[A:%.*]] to i128
-; CHECK-NEXT:    [[SEXT_B:%.*]] = sext i1 [[B:%.*]] to i128
-; CHECK-NEXT:    [[ADD:%.*]] = add nsw i128 [[ZEXT_A]], [[SEXT_B]]
-; CHECK-NEXT:    [[R:%.*]] = icmp sgt i128 [[ADD]], 9223372036854775808
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %zext.a = zext i1 %a to i128
   %sext.b = sext i1 %b to i128
@@ -704,12 +694,12 @@ define i1 @zext_sext_add_icmp_i128(i1 %a, i1 %b) {
   ret i1 %r
 }
 
+; (zext i1 a) + (sext i1 b)) == -1 --> ~a & b
+
 define i1 @zext_sext_add_icmp_eq_minus1(i1 %a, i1 %b) {
 ; CHECK-LABEL: @zext_sext_add_icmp_eq_minus1(
-; CHECK-NEXT:    [[ZEXT_A:%.*]] = zext i1 [[A:%.*]] to i8
-; CHECK-NEXT:    [[SEXT_B:%.*]] = sext i1 [[B:%.*]] to i8
-; CHECK-NEXT:    [[ADD:%.*]] = add nsw i8 [[ZEXT_A]], [[SEXT_B]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[ADD]], -1
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i1 [[A:%.*]], true
+; CHECK-NEXT:    [[R:%.*]] = and i1 [[TMP1]], [[B:%.*]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %zext.a = zext i1 %a to i8
@@ -719,12 +709,13 @@ define i1 @zext_sext_add_icmp_eq_minus1(i1 %a, i1 %b) {
   ret i1 %r
 }
 
+
+; (zext i1 a) + (sext i1 b)) != -1 --> a | ~b
+
 define i1 @zext_sext_add_icmp_ne_minus1(i1 %a, i1 %b) {
 ; CHECK-LABEL: @zext_sext_add_icmp_ne_minus1(
-; CHECK-NEXT:    [[ZEXT_A:%.*]] = zext i1 [[A:%.*]] to i8
-; CHECK-NEXT:    [[SEXT_B:%.*]] = sext i1 [[B:%.*]] to i8
-; CHECK-NEXT:    [[ADD:%.*]] = add nsw i8 [[ZEXT_A]], [[SEXT_B]]
-; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[ADD]], -1
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i1 [[B:%.*]], true
+; CHECK-NEXT:    [[R:%.*]] = or i1 [[TMP1]], [[A:%.*]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %zext.a = zext i1 %a to i8
@@ -734,10 +725,12 @@ define i1 @zext_sext_add_icmp_ne_minus1(i1 %a, i1 %b) {
   ret i1 %r
 }
 
+; (zext i1 a) + (sext i1 b)) s> -1 --> a | ~b
+
 define i1 @zext_sext_add_icmp_sgt_minus1(i1 %a, i1 %b) {
 ; CHECK-LABEL: @zext_sext_add_icmp_sgt_minus1(
-; CHECK-NEXT:    [[B_NOT:%.*]] = xor i1 [[B:%.*]], true
-; CHECK-NEXT:    [[R:%.*]] = or i1 [[B_NOT]], [[A:%.*]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i1 [[B:%.*]], true
+; CHECK-NEXT:    [[R:%.*]] = or i1 [[TMP1]], [[A:%.*]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %zext.a = zext i1 %a to i8
@@ -747,12 +740,12 @@ define i1 @zext_sext_add_icmp_sgt_minus1(i1 %a, i1 %b) {
   ret i1 %r
 }
 
+; (zext i1 a) + (sext i1 b)) u< -1 --> a | ~b
+
 define i1 @zext_sext_add_icmp_ult_minus1(i1 %a, i1 %b) {
 ; CHECK-LABEL: @zext_sext_add_icmp_ult_minus1(
-; CHECK-NEXT:    [[ZEXT_A:%.*]] = zext i1 [[A:%.*]] to i8
-; CHECK-NEXT:    [[SEXT_B:%.*]] = sext i1 [[B:%.*]] to i8
-; CHECK-NEXT:    [[ADD:%.*]] = add nsw i8 [[ZEXT_A]], [[SEXT_B]]
-; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[ADD]], -1
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i1 [[B:%.*]], true
+; CHECK-NEXT:    [[R:%.*]] = or i1 [[TMP1]], [[A:%.*]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %zext.a = zext i1 %a to i8
@@ -762,12 +755,12 @@ define i1 @zext_sext_add_icmp_ult_minus1(i1 %a, i1 %b) {
   ret i1 %r
 }
 
+; (zext i1 a) + (sext i1 b)) s> 0 --> a & ~b
+
 define i1 @zext_sext_add_icmp_sgt_0(i1 %a, i1 %b) {
 ; CHECK-LABEL: @zext_sext_add_icmp_sgt_0(
-; CHECK-NEXT:    [[ZEXT_A:%.*]] = zext i1 [[A:%.*]] to i8
-; CHECK-NEXT:    [[SEXT_B:%.*]] = sext i1 [[B:%.*]] to i8
-; CHECK-NEXT:    [[ADD:%.*]] = add nsw i8 [[ZEXT_A]], [[SEXT_B]]
-; CHECK-NEXT:    [[R:%.*]] = icmp sgt i8 [[ADD]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i1 [[B:%.*]], true
+; CHECK-NEXT:    [[R:%.*]] = and i1 [[TMP1]], [[A:%.*]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %zext.a = zext i1 %a to i8
@@ -777,11 +770,13 @@ define i1 @zext_sext_add_icmp_sgt_0(i1 %a, i1 %b) {
   ret i1 %r
 }
 
+; (zext i1 a) + (sext i1 b)) s< 0 --> ~a & b
+
 define i1 @zext_sext_add_icmp_slt_0(i1 %a, i1 %b) {
 ; CHECK-LABEL: @zext_sext_add_icmp_slt_0(
 ; CHECK-NEXT:    [[TMP1:%.*]] = xor i1 [[A:%.*]], true
-; CHECK-NEXT:    [[TMP2:%.*]] = and i1 [[TMP1]], [[B:%.*]]
-; CHECK-NEXT:    ret i1 [[TMP2]]
+; CHECK-NEXT:    [[R:%.*]] = and i1 [[TMP1]], [[B:%.*]]
+; CHECK-NEXT:    ret i1 [[R]]
 ;
   %zext.a = zext i1 %a to i8
   %sext.b = sext i1 %b to i8
@@ -790,12 +785,12 @@ define i1 @zext_sext_add_icmp_slt_0(i1 %a, i1 %b) {
   ret i1 %r
 }
 
+; (zext i1 a) + (sext i1 b)) == 1 --> a & ~b
+
 define i1 @zext_sext_add_icmp_eq_1(i1 %a, i1 %b) {
 ; CHECK-LABEL: @zext_sext_add_icmp_eq_1(
-; CHECK-NEXT:    [[ZEXT_A:%.*]] = zext i1 [[A:%.*]] to i8
-; CHECK-NEXT:    [[SEXT_B:%.*]] = sext i1 [[B:%.*]] to i8
-; CHECK-NEXT:    [[ADD:%.*]] = add nsw i8 [[ZEXT_A]], [[SEXT_B]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[ADD]], 1
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i1 [[B:%.*]], true
+; CHECK-NEXT:    [[R:%.*]] = and i1 [[TMP1]], [[A:%.*]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %zext.a = zext i1 %a to i8
@@ -805,12 +800,12 @@ define i1 @zext_sext_add_icmp_eq_1(i1 %a, i1 %b) {
   ret i1 %r
 }
 
+; (zext i1 a) + (sext i1 b)) != 1 --> ~a | b
+
 define i1 @zext_sext_add_icmp_ne_1(i1 %a, i1 %b) {
 ; CHECK-LABEL: @zext_sext_add_icmp_ne_1(
-; CHECK-NEXT:    [[ZEXT_A:%.*]] = zext i1 [[A:%.*]] to i8
-; CHECK-NEXT:    [[SEXT_B:%.*]] = sext i1 [[B:%.*]] to i8
-; CHECK-NEXT:    [[ADD:%.*]] = add nsw i8 [[ZEXT_A]], [[SEXT_B]]
-; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[ADD]], 1
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i1 [[A:%.*]], true
+; CHECK-NEXT:    [[R:%.*]] = or i1 [[TMP1]], [[B:%.*]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %zext.a = zext i1 %a to i8
@@ -820,12 +815,12 @@ define i1 @zext_sext_add_icmp_ne_1(i1 %a, i1 %b) {
   ret i1 %r
 }
 
+; (zext i1 a) + (sext i1 b)) s< 1 --> ~a | b
+
 define i1 @zext_sext_add_icmp_slt_1(i1 %a, i1 %b) {
 ; CHECK-LABEL: @zext_sext_add_icmp_slt_1(
-; CHECK-NEXT:    [[ZEXT_A:%.*]] = zext i1 [[A:%.*]] to i8
-; CHECK-NEXT:    [[SEXT_B:%.*]] = sext i1 [[B:%.*]] to i8
-; CHECK-NEXT:    [[ADD:%.*]] = add nsw i8 [[ZEXT_A]], [[SEXT_B]]
-; CHECK-NEXT:    [[R:%.*]] = icmp slt i8 [[ADD]], 1
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i1 [[A:%.*]], true
+; CHECK-NEXT:    [[R:%.*]] = or i1 [[TMP1]], [[B:%.*]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %zext.a = zext i1 %a to i8
@@ -835,11 +830,13 @@ define i1 @zext_sext_add_icmp_slt_1(i1 %a, i1 %b) {
   ret i1 %r
 }
 
+; (zext i1 a) + (sext i1 b)) u> 1 --> ~a & b
+
 define i1 @zext_sext_add_icmp_ugt_1(i1 %a, i1 %b) {
 ; CHECK-LABEL: @zext_sext_add_icmp_ugt_1(
 ; CHECK-NEXT:    [[TMP1:%.*]] = xor i1 [[A:%.*]], true
-; CHECK-NEXT:    [[TMP2:%.*]] = and i1 [[TMP1]], [[B:%.*]]
-; CHECK-NEXT:    ret i1 [[TMP2]]
+; CHECK-NEXT:    [[R:%.*]] = and i1 [[TMP1]], [[B:%.*]]
+; CHECK-NEXT:    ret i1 [[R]]
 ;
   %zext.a = zext i1 %a to i8
   %sext.b = sext i1 %b to i8
@@ -850,10 +847,8 @@ define i1 @zext_sext_add_icmp_ugt_1(i1 %a, i1 %b) {
 
 define <2 x i1> @vector_zext_sext_add_icmp_slt_1(<2 x i1> %a, <2 x i1> %b) {
 ; CHECK-LABEL: @vector_zext_sext_add_icmp_slt_1(
-; CHECK-NEXT:    [[ZEXT_A:%.*]] = zext <2 x i1> [[A:%.*]] to <2 x i8>
-; CHECK-NEXT:    [[SEXT_B:%.*]] = sext <2 x i1> [[B:%.*]] to <2 x i8>
-; CHECK-NEXT:    [[ADD:%.*]] = add nsw <2 x i8> [[ZEXT_A]], [[SEXT_B]]
-; CHECK-NEXT:    [[R:%.*]] = icmp slt <2 x i8> [[ADD]], <i8 1, i8 1>
+; CHECK-NEXT:    [[TMP1:%.*]] = xor <2 x i1> [[A:%.*]], <i1 true, i1 true>
+; CHECK-NEXT:    [[R:%.*]] = or <2 x i1> [[TMP1]], [[B:%.*]]
 ; CHECK-NEXT:    ret <2 x i1> [[R]]
 ;
   %zext.a = zext <2 x i1> %a to <2 x i8>
@@ -878,6 +873,8 @@ define <2 x i1> @vector_zext_sext_add_icmp_slt_1_poison(<2 x i1> %a, <2 x i1> %b
   ret <2 x i1> %r
 }
 
+; Negative test, more than one use for icmp LHS
+
 define i1 @zext_sext_add_icmp_slt_1_no_oneuse(i1 %a, i1 %b) {
 ; CHECK-LABEL: @zext_sext_add_icmp_slt_1_no_oneuse(
 ; CHECK-NEXT:    [[ZEXT_A:%.*]] = zext i1 [[A:%.*]] to i8
@@ -895,6 +892,8 @@ define i1 @zext_sext_add_icmp_slt_1_no_oneuse(i1 %a, i1 %b) {
   ret i1 %r
 }
 
+; Negative test, icmp RHS is not a constant
+
 define i1 @zext_sext_add_icmp_slt_1_rhs_not_const(i1 %a, i1 %b, i8 %c) {
 ; CHECK-LABEL: @zext_sext_add_icmp_slt_1_rhs_not_const(
 ; CHECK-NEXT:    [[ZEXT_A:%.*]] = zext i1 [[A:%.*]] to i8
@@ -910,6 +909,8 @@ define i1 @zext_sext_add_icmp_slt_1_rhs_not_const(i1 %a, i1 %b, i8 %c) {
   ret i1 %r
 }
 
+; Negative test, ext source is not i1
+
 define i1 @zext_sext_add_icmp_slt_1_type_not_i1(i2 %a, i1 %b) {
 ; CHECK-LABEL: @zext_sext_add_icmp_slt_1_type_not_i1(
 ; CHECK-NEXT:    [[ZEXT_A:%.*]] = zext i2 [[A:%.*]] to i8