commit ee8d6acb1f5c175c1d2c4d892149421b0fe285ed
author Xinliang David Li <davidxl@google.com> Thu Jun 01 19:05:55 2017 +0000
committer Xinliang David Li <davidxl@google.com> Thu Jun 01 19:05:55 2017 +0000
tree 807de8b63127c5f1be7ff6a55cb37286444fce64
parent 0a0acbcf78ce1b9169f62d2fc13d169826daf114

[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

llvm/lib/Transforms/Scalar/LowerExpectIntrinsic.cpp

diff --git a/llvm/lib/Transforms/Scalar/LowerExpectIntrinsic.cpp b/llvm/lib/Transforms/Scalar/LowerExpectIntrinsic.cpp
index a143b9a..930696b 100644
--- a/llvm/lib/Transforms/Scalar/LowerExpectIntrinsic.cpp
+++ b/llvm/lib/Transforms/Scalar/LowerExpectIntrinsic.cpp
@@ -98,11 +98,20 @@
   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 @@
   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);