[InstCombine] Use APInt::getBitsSetFrom instead of inverting the result of getLowBits...

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300265 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 2419d4f..5a292ef 100644 (file)
--- a/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -3810,16 +3810,14 @@ static APInt getDemandedBitsLHSMask(ICmpInst &I, unsigned BitWidth,
   // greater than the RHS must differ in a bit higher than these due to carry.
   case ICmpInst::ICMP_UGT: {
     unsigned trailingOnes = RHS.countTrailingOnes();
-    APInt lowBitsSet = APInt::getLowBitsSet(BitWidth, trailingOnes);
-    return ~lowBitsSet;
+    return APInt::getBitsSetFrom(BitWidth, trailingOnes);
   }
 
   // Similarly, for a ULT comparison, we don't care about the trailing zeros.
   // Any value less than the RHS must differ in a higher bit because of carries.
   case ICmpInst::ICMP_ULT: {
     unsigned trailingZeros = RHS.countTrailingZeros();
-    APInt lowBitsSet = APInt::getLowBitsSet(BitWidth, trailingZeros);
-    return ~lowBitsSet;
+    return APInt::getBitsSetFrom(BitWidth, trailingZeros);
   }
 
   default: