Always compute all the bits in ComputeMaskedBits.

This allows us to keep passing reduced masks to SimplifyDemandedBits, but
know about all the bits if SimplifyDemandedBits fails. This allows instcombine
to simplify cases like the one in the included testcase.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154011 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 6 deletions

diff --git a/lib/Analysis/Lint.cpp b/lib/Analysis/Lint.cpp
index 971065f8d4..83bdf5286a 100644
--- a/lib/Analysis/Lint.cpp
+++ b/lib/Analysis/Lint.cpp
@@ -416,9 +416,8 @@ void Lint::visitMemoryReference(Instruction &I,
 
     if (Align != 0) {
       unsigned BitWidth = TD->getTypeSizeInBits(Ptr->getType());
-      APInt Mask = APInt::getAllOnesValue(BitWidth),
-                   KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
-      ComputeMaskedBits(Ptr, Mask, KnownZero, KnownOne, TD);
+      APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
+      ComputeMaskedBits(Ptr, KnownZero, KnownOne, TD);
       Assert1(!(KnownOne & APInt::getLowBitsSet(BitWidth, Log2_32(Align))),
               "Undefined behavior: Memory reference address is misaligned", &I);
     }
@@ -476,9 +475,8 @@ static bool isZero(Value *V, TargetData *TD) {
   if (isa<UndefValue>(V)) return true;
 
   unsigned BitWidth = cast<IntegerType>(V->getType())->getBitWidth();
-  APInt Mask = APInt::getAllOnesValue(BitWidth),
-               KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
-  ComputeMaskedBits(V, Mask, KnownZero, KnownOne, TD);
+  APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
+  ComputeMaskedBits(V, KnownZero, KnownOne, TD);
   return KnownZero.isAllOnesValue();
 }