X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=blobdiff_plain;f=lib%2FAnalysis%2FBranchProbabilityInfo.cpp;h=d7cee3afaf5975c7d0e508fd738f14f2ce273434;hp=14800f4a28bfb3333e420c8db2243d1fd194b804;hb=058309ba87896d28a995118f5415011caa97cfbe;hpb=29da6378264333420481f421b05078ce0af58e0a

diff --git a/lib/Analysis/BranchProbabilityInfo.cpp b/lib/Analysis/BranchProbabilityInfo.cpp
index 14800f4a28b..d7cee3afaf5 100644
--- a/lib/Analysis/BranchProbabilityInfo.cpp
+++ b/lib/Analysis/BranchProbabilityInfo.cpp
@@ -379,6 +379,14 @@ bool BranchProbabilityInfo::calcZeroHeuristics(BasicBlock *BB) {
   if (!CV)
     return false;
 
+  // If the LHS is the result of AND'ing a value with a single bit bitmask,
+  // we don't have information about probabilities.
+  if (Instruction *LHS = dyn_cast<Instruction>(CI->getOperand(0)))
+    if (LHS->getOpcode() == Instruction::And)
+      if (ConstantInt *AndRHS = dyn_cast<ConstantInt>(LHS->getOperand(1)))
+        if (AndRHS->getUniqueInteger().isPowerOf2())
+          return false;
+
   bool isProb;
   if (CV->isZero()) {
     switch (CI->getPredicate()) {