A shift of a power of two is a power of two or zero.
For completeness - not spotted in the wild.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143211 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index 90757f9..9f7b5b5 100644
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -769,6 +769,12 @@
if (Depth++ == MaxDepth)
return false;
+ Value *X = 0, *Y = 0;
+ // A shift of a power of two is a power of two or zero.
+ if (OrZero && (match(V, m_Shl(m_Value(X), m_Value())) ||
+ match(V, m_Shr(m_Value(X), m_Value()))))
+ return isPowerOfTwo(X, TD, /*OrZero*/true, Depth);
+
if (ZExtInst *ZI = dyn_cast<ZExtInst>(V))
return isPowerOfTwo(ZI->getOperand(0), TD, OrZero, Depth);
@@ -776,7 +782,6 @@
return isPowerOfTwo(SI->getTrueValue(), TD, OrZero, Depth) &&
isPowerOfTwo(SI->getFalseValue(), TD, OrZero, Depth);
- Value *X = 0, *Y = 0;
if (OrZero && match(V, m_And(m_Value(X), m_Value(Y)))) {
// A power of two and'd with anything is a power of two or zero.
if (isPowerOfTwo(X, TD, /*OrZero*/true, Depth) ||