Add a m_SignBit pattern for convenience.

llvm-svn: 124656

2 files changed, 16 insertions, 3 deletions

diff --git a/llvm/include/llvm/Support/PatternMatch.h b/llvm/include/llvm/Support/PatternMatch.h
index b203c1ee1a5..ea065a769ec 100644
--- a/llvm/include/llvm/Support/PatternMatch.h
+++ b/llvm/include/llvm/Support/PatternMatch.h
@@ -116,6 +116,21 @@ struct all_ones_ty {
 /// m_AllOnes() - Match an integer or vector with all bits set to true.
 inline all_ones_ty m_AllOnes() { return all_ones_ty(); }
 
+struct signbit_ty {
+  template<typename ITy>
+  bool match(ITy *V) {
+    if (const ConstantInt *CI = dyn_cast<ConstantInt>(V))
+      return CI->getValue().isSignBit();
+    if (const ConstantVector *CV = dyn_cast<ConstantVector>(V))
+      if (ConstantInt *CI = cast_or_null<ConstantInt>(CV->getSplatValue()))
+        return CI->getValue().isSignBit();
+    return false;
+  }
+};
+
+/// m_SignBit() - Match an integer or vector with only the sign bit(s) set.
+inline signbit_ty m_SignBit() { return signbit_ty(); }
+
 
 template<typename Class>
 struct bind_ty {
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 72b3f03a93a..44c1b5326bc 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -666,9 +666,7 @@ bool llvm::isPowerOfTwo(Value *V, const TargetData *TD, unsigned Depth) {
 
   // (signbit) >>l X is clearly a power of two if the one is not shifted off the
   // bottom.  If it is shifted off the bottom then the result is undefined.
-  ConstantInt *CI;
-  if (match(V, m_LShr(m_ConstantInt(CI), m_Value())) &&
-      CI->getValue().isSignBit())
+  if (match(V, m_LShr(m_SignBit(), m_Value())))
     return true;
 
   // The remaining tests are all recursive, so bail out if we hit the limit.