[ValueTracking] Simplify the known bits code for constant vectors a little.

Neither of these cases really require a temporary APInt outside the loop. For the ConstantDataSequential case the APInt will never be larger than 64-bits so its fine to just call getElementAsAPInt. For ConstantVector we can get the APInt by reference and only make a copy where the inversion is needed.

llvm-svn: 316265

1 files changed, 2 insertions, 4 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 750e6bd..244bc7d 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -1507,9 +1507,8 @@ void computeKnownBits(const Value *V, KnownBits &Known, unsigned Depth,
     // We know that CDS must be a vector of integers. Take the intersection of
     // each element.
     Known.Zero.setAllBits(); Known.One.setAllBits();
-    APInt Elt(BitWidth, 0);
     for (unsigned i = 0, e = CDS->getNumElements(); i != e; ++i) {
-      Elt = CDS->getElementAsInteger(i);
+      APInt Elt = CDS->getElementAsAPInt(i);
       Known.Zero &= ~Elt;
       Known.One &= Elt;
     }
@@ -1520,7 +1519,6 @@ void computeKnownBits(const Value *V, KnownBits &Known, unsigned Depth,
     // We know that CV must be a vector of integers. Take the intersection of
     // each element.
     Known.Zero.setAllBits(); Known.One.setAllBits();
-    APInt Elt(BitWidth, 0);
     for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) {
       Constant *Element = CV->getAggregateElement(i);
       auto *ElementCI = dyn_cast_or_null<ConstantInt>(Element);
@@ -1528,7 +1526,7 @@ void computeKnownBits(const Value *V, KnownBits &Known, unsigned Depth,
         Known.resetAll();
         return;
       }
-      Elt = ElementCI->getValue();
+      const APInt &Elt = ElementCI->getValue();
       Known.Zero &= ~Elt;
       Known.One &= Elt;
     }