[llvm] r300849 - In SimplifyDemandedUseBits, use computeKnownBits directly to handle Constants

[Craig Topper via llvm-commits]

Author: ctopper
Date: Thu Apr 20 11:14:58 2017
New Revision: 300849

URL: http://llvm.org/viewvc/llvm-project?rev=300849&view=rev
Log:
In SimplifyDemandedUseBits, use computeKnownBits directly to handle Constants

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


Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp?rev=300849&r1=300848&r2=300849&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp Thu Apr 20 11:14:58 2017
@@ -117,27 +117,16 @@ Value *InstCombiner::SimplifyDemandedUse
       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;