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.

llvm-svn: 35019

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
index a1d9e978329..9d327c7883d 100644
--- a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/llvm/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