For PR1205:

Provide an APIntified version of MaskedValueIsZero. This will (temporarily)
cause a "defined but not used" message from the compiler. It will be used
in the next patch in this series.

Patch by Sheng Zhou.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35019 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index a1d9e978329554fb61e68dd84a5603c829c87b05..9d327c7883d3614d958dd9309540a3fadc4fca3c 100644 (file)
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -979,6 +979,16 @@ static bool MaskedValueIsZero(Value *V, uint64_t Mask, unsigned Depth = 0) {
   return (KnownZero & Mask) == Mask;
 }
 
+/// MaskedValueIsZero - Return true if 'V & Mask' is known to be zero.  We use
+/// this predicate to simplify operations downstream.  Mask is known to be zero
+/// for bits that V cannot have.
+static bool MaskedValueIsZero(Value *V, const APInt& Mask, unsigned Depth = 0) {
+  APInt KnownZero(Mask), KnownOne(Mask);
+  ComputeMaskedBits(V, Mask, KnownZero, KnownOne, Depth);
+  assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 
+  return (KnownZero & Mask) == Mask;
+}
+
 /// ShrinkDemandedConstant - Check to see if the specified operand of the 
 /// specified instruction is a constant integer.  If so, check to see if there
 /// are any bits set in the constant that are not demanded.  If so, shrink the