[llvm-commits] [llvm] r143211 - in /llvm/trunk: lib/Analysis/ValueTracking.cpp test/Transforms/InstSimplify/AndOrXor.ll
Duncan Sands
baldrick at free.fr
Fri Oct 28 11:30:05 PDT 2011
Author: baldrick
Date: Fri Oct 28 13:30:05 2011
New Revision: 143211
URL: http://llvm.org/viewvc/llvm-project?rev=143211&view=rev
Log:
A shift of a power of two is a power of two or zero.
For completeness - not spotted in the wild.
Modified:
llvm/trunk/lib/Analysis/ValueTracking.cpp
llvm/trunk/test/Transforms/InstSimplify/AndOrXor.ll
Modified: llvm/trunk/lib/Analysis/ValueTracking.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ValueTracking.cpp?rev=143211&r1=143210&r2=143211&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ValueTracking.cpp (original)
+++ llvm/trunk/lib/Analysis/ValueTracking.cpp Fri Oct 28 13:30:05 2011
@@ -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) ||
Modified: llvm/trunk/test/Transforms/InstSimplify/AndOrXor.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstSimplify/AndOrXor.ll?rev=143211&r1=143210&r2=143211&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstSimplify/AndOrXor.ll (original)
+++ llvm/trunk/test/Transforms/InstSimplify/AndOrXor.ll Fri Oct 28 13:30:05 2011
@@ -10,3 +10,13 @@
ret i64 %e2
; CHECK: ret i64 %e
}
+
+define i64 @pow2b(i32 %x) {
+; CHECK: @pow2b
+ %sh = shl i32 2, %x
+ %e = zext i32 %sh to i64
+ %nege = sub i64 0, %e
+ %e2 = and i64 %e, %nege
+ ret i64 %e2
+; CHECK: ret i64 %e
+}
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