In SimplifyDemandedUseBits, use computeKnownBits directly to handle C…

…onstants

Currently we don't explicitly process ConstantDataSequential, ConstantAggregateZero, or ConstantVector, or Undef before applying the Depth limit. Instead they occur after the depth check in the non-instruction path.

For the constant types that we do handle, the code is replicated from computeKnownBits.

This patch fixes the missing constant handling and the reduces the amount of code by just using computeKnownBits directly for any type of Constant.

Differential Revision: https://reviews.llvm.org/D32123



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300849 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp

@@ -117,27 +117,16 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
       KnownOne.getBitWidth() == BitWidth &&
       "Value *V, DemandedMask, KnownZero and KnownOne "
       "must have same BitWidth");
-  const APInt *C;
-  if (match(V, m_APInt(C))) {
-    // We know all of the bits for a scalar constant or a splat vector constant!
-    KnownOne = *C;
-    KnownZero = ~KnownOne;
-    return nullptr;
-  }
-  if (isa<ConstantPointerNull>(V)) {
-    // We know all of the bits for a constant!
-    KnownOne.clearAllBits();
-    KnownZero.setAllBits();
+
+  if (isa<Constant>(V)) {
+    computeKnownBits(V, KnownZero, KnownOne, Depth, CxtI);
     return nullptr;
   }
 
   KnownZero.clearAllBits();
   KnownOne.clearAllBits();
-  if (DemandedMask == 0) {   // Not demanding any bits from V.
-    if (isa<UndefValue>(V))
-      return nullptr;
+  if (DemandedMask == 0)     // Not demanding any bits from V.
     return UndefValue::get(VTy);
-  }
 
   if (Depth == 6)        // Limit search depth.
     return nullptr;