[Profile] Fix builtin_expect lowering bug

The lowerer wrongly assumes the ICMP instruction 
 1) always has a constant operand;
 2) the operand has value 0.

It also assumes the expected value can only be one, thus
other values other than one will be considered 'zero'.

This leads to wrong profile annotation when other integer values
are used other than 0, 1 in the comparison or in the expect intrinsic.

Also missing is handling of equal predicate.

This patch fixes all the above problems.

Differential Revision: http://reviews.llvm.org/D33757

llvm-svn: 304453

1 files changed, 12 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/Scalar/LowerExpectIntrinsic.cpp b/llvm/lib/Transforms/Scalar/LowerExpectIntrinsic.cpp
index a143b9a3c64..930696b036c 100644
--- a/llvm/lib/Transforms/Scalar/LowerExpectIntrinsic.cpp
+++ b/llvm/lib/Transforms/Scalar/LowerExpectIntrinsic.cpp
@@ -98,11 +98,20 @@ template <class BrSelInst> static bool handleBrSelExpect(BrSelInst &BSI) {
   CallInst *CI;
 
   ICmpInst *CmpI = dyn_cast<ICmpInst>(BSI.getCondition());
+  CmpInst::Predicate Predicate;
+  uint64_t ValueComparedTo = 0;
   if (!CmpI) {
     CI = dyn_cast<CallInst>(BSI.getCondition());
+    Predicate = CmpInst::ICMP_NE;
+    ValueComparedTo = 0;
   } else {
-    if (CmpI->getPredicate() != CmpInst::ICMP_NE)
+    Predicate = CmpI->getPredicate();
+    if (Predicate != CmpInst::ICMP_NE && Predicate != CmpInst::ICMP_EQ)
       return false;
+    ConstantInt *CmpConstOperand = dyn_cast<ConstantInt>(CmpI->getOperand(1));
+    if (!CmpConstOperand)
+      return false;
+    ValueComparedTo = CmpConstOperand->getZExtValue();
     CI = dyn_cast<CallInst>(CmpI->getOperand(0));
   }
 
@@ -121,9 +130,8 @@ template <class BrSelInst> static bool handleBrSelExpect(BrSelInst &BSI) {
   MDBuilder MDB(CI->getContext());
   MDNode *Node;
 
-  // If expect value is equal to 1 it means that we are more likely to take
-  // branch 0, in other case more likely is branch 1.
-  if (ExpectedValue->isOne())
+  if ((ExpectedValue->getZExtValue() == ValueComparedTo) ==
+      (Predicate == CmpInst::ICMP_EQ))
     Node = MDB.createBranchWeights(LikelyBranchWeight, UnlikelyBranchWeight);
   else
     Node = MDB.createBranchWeights(UnlikelyBranchWeight, LikelyBranchWeight);