[InstCombine] Teach foldICmpUsingKnownBits to simplify SLE/SGE/ULE/UGE to equality comparisons when the min/max ranges intersect in a single value.

This is the inverse of what we do for SGT/SLT/UGT/ULT.

llvm-svn: 314032

2 files changed, 12 insertions, 8 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index a9911f42cba..f38618e85e8 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -4272,6 +4272,8 @@ Instruction *InstCombiner::foldICmpUsingKnownBits(ICmpInst &I) {
       return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
     if (Op0Max.slt(Op1Min)) // A >=s B -> false if max(A) < min(B)
       return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
+    if (Op1Min == Op0Max) // A >=s B -> A == B if max(A) == min(B)
+      return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
     break;
   case ICmpInst::ICMP_SLE:
     assert(!isa<ConstantInt>(Op1) && "ICMP_SLE with ConstantInt not folded!");
@@ -4279,6 +4281,8 @@ Instruction *InstCombiner::foldICmpUsingKnownBits(ICmpInst &I) {
       return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
     if (Op0Min.sgt(Op1Max)) // A <=s B -> false if min(A) > max(B)
       return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
+    if (Op1Max == Op0Min) // A <=s B -> A == B if min(A) == max(B)
+      return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
     break;
   case ICmpInst::ICMP_UGE:
     assert(!isa<ConstantInt>(Op1) && "ICMP_UGE with ConstantInt not folded!");
@@ -4286,6 +4290,8 @@ Instruction *InstCombiner::foldICmpUsingKnownBits(ICmpInst &I) {
       return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
     if (Op0Max.ult(Op1Min)) // A >=u B -> false if max(A) < min(B)
       return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
+    if (Op1Min == Op0Max) // A >=u B -> A == B if max(A) == min(B)
+      return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
     break;
   case ICmpInst::ICMP_ULE:
     assert(!isa<ConstantInt>(Op1) && "ICMP_ULE with ConstantInt not folded!");
@@ -4293,6 +4299,8 @@ Instruction *InstCombiner::foldICmpUsingKnownBits(ICmpInst &I) {
       return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
     if (Op0Min.ugt(Op1Max)) // A <=u B -> false if min(A) > max(B)
       return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
+    if (Op1Max == Op0Min) // A <=u B -> A == B if min(A) == max(B)
+      return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
     break;
   }
 
diff --git a/llvm/test/Transforms/InstCombine/icmp.ll b/llvm/test/Transforms/InstCombine/icmp.ll
index 014d8152248..68d98de0b4e 100644
--- a/llvm/test/Transforms/InstCombine/icmp.ll
+++ b/llvm/test/Transforms/InstCombine/icmp.ll
@@ -3070,14 +3070,13 @@ define <8 x i1> @bitreverse_vec_ne(<8 x i16> %x, <8 x i16> %y) {
 
 ; These perform a comparison of a value known to be between 4 and 5 with a value between 5 and 7.
 ; They should all simplify to equality compares.
-; FIXME this should simplify to an equality comparison
 define i1 @knownbits1(i8 %a, i8 %b) {
 ; CHECK-LABEL: @knownbits1(
 ; CHECK-NEXT:    [[A1:%.*]] = and i8 [[A:%.*]], 1
 ; CHECK-NEXT:    [[A2:%.*]] = or i8 [[A1]], 4
 ; CHECK-NEXT:    [[B1:%.*]] = and i8 [[B:%.*]], 2
 ; CHECK-NEXT:    [[B2:%.*]] = or i8 [[B1]], 5
-; CHECK-NEXT:    [[C:%.*]] = icmp uge i8 [[A2]], [[B2]]
+; CHECK-NEXT:    [[C:%.*]] = icmp eq i8 [[A2]], [[B2]]
 ; CHECK-NEXT:    ret i1 [[C]]
 ;
   %a1 = and i8 %a, 5
@@ -3105,14 +3104,13 @@ define i1 @knownbits2(i8 %a, i8 %b) {
   ret i1 %c
 }
 
-; FIXME this should simplify to an equality comparison
 define i1 @knownbits3(i8 %a, i8 %b) {
 ; CHECK-LABEL: @knownbits3(
 ; CHECK-NEXT:    [[A1:%.*]] = and i8 [[A:%.*]], 1
 ; CHECK-NEXT:    [[A2:%.*]] = or i8 [[A1]], 4
 ; CHECK-NEXT:    [[B1:%.*]] = and i8 [[B:%.*]], 2
 ; CHECK-NEXT:    [[B2:%.*]] = or i8 [[B1]], 5
-; CHECK-NEXT:    [[C:%.*]] = icmp ule i8 [[B2]], [[A2]]
+; CHECK-NEXT:    [[C:%.*]] = icmp eq i8 [[B2]], [[A2]]
 ; CHECK-NEXT:    ret i1 [[C]]
 ;
   %a1 = and i8 %a, 5
@@ -3142,14 +3140,13 @@ define <2 x i1> @knownbits4(<2 x i8> %a, <2 x i8> %b) {
 
 ; These are the signed versions of the above. One value is less than or equal to 5, but maybe negative.
 ; The other is known to be a value 5-7. These should simplify to equality comparisons.
-; FIXME this should simplify to an equality comparison
 define i1 @knownbits5(i8 %a, i8 %b) {
 ; CHECK-LABEL: @knownbits5(
 ; CHECK-NEXT:    [[A1:%.*]] = and i8 [[A:%.*]], -127
 ; CHECK-NEXT:    [[A2:%.*]] = or i8 [[A1]], 4
 ; CHECK-NEXT:    [[B1:%.*]] = and i8 [[B:%.*]], 2
 ; CHECK-NEXT:    [[B2:%.*]] = or i8 [[B1]], 5
-; CHECK-NEXT:    [[C:%.*]] = icmp sge i8 [[A2]], [[B2]]
+; CHECK-NEXT:    [[C:%.*]] = icmp eq i8 [[A2]], [[B2]]
 ; CHECK-NEXT:    ret i1 [[C]]
 ;
   %a1 = and i8 %a, 133
@@ -3177,14 +3174,13 @@ define i1 @knownbits6(i8 %a, i8 %b) {
   ret i1 %c
 }
 
-; FIXME this should simplify to an equality comparison
 define <2 x i1> @knownbits7(<2 x i8> %a, <2 x i8> %b) {
 ; CHECK-LABEL: @knownbits7(
 ; CHECK-NEXT:    [[A1:%.*]] = and <2 x i8> [[A:%.*]], <i8 -127, i8 -127>
 ; CHECK-NEXT:    [[A2:%.*]] = or <2 x i8> [[A1]], <i8 4, i8 4>
 ; CHECK-NEXT:    [[B1:%.*]] = and <2 x i8> [[B:%.*]], <i8 2, i8 2>
 ; CHECK-NEXT:    [[B2:%.*]] = or <2 x i8> [[B1]], <i8 5, i8 5>
-; CHECK-NEXT:    [[C:%.*]] = icmp sle <2 x i8> [[B2]], [[A2]]
+; CHECK-NEXT:    [[C:%.*]] = icmp eq <2 x i8> [[B2]], [[A2]]
 ; CHECK-NEXT:    ret <2 x i1> [[C]]
 ;
   %a1 = and <2 x i8> %a, <i8 133, i8 133>