Lower llvm.expect intrinsic correctly for i1

LowerExpectIntrinsic previously only understood the idiom of an expect
intrinsic followed by a comparison with zero. For llvm.expect.i1, the
comparison would be stripped by the early-cse pass.

Patch by Daniel Micay.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200664 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 18 insertions, 5 deletions

diff --git a/lib/Transforms/Utils/LowerExpectIntrinsic.cpp b/lib/Transforms/Utils/LowerExpectIntrinsic.cpp
index e017f50120..596fd37115 100644
--- a/lib/Transforms/Utils/LowerExpectIntrinsic.cpp
+++ b/lib/Transforms/Utils/LowerExpectIntrinsic.cpp
@@ -94,15 +94,25 @@ bool LowerExpectIntrinsic::HandleIfExpect(BranchInst *BI) {
     return false;
 
   // Handle non-optimized IR code like:
-  //   %expval = call i64 @llvm.expect.i64.i64(i64 %conv1, i64 1)
+  //   %expval = call i64 @llvm.expect.i64(i64 %conv1, i64 1)
   //   %tobool = icmp ne i64 %expval, 0
   //   br i1 %tobool, label %if.then, label %if.end
+  //
+  // Or the following simpler case:
+  //   %expval = call i1 @llvm.expect.i1(i1 %cmp, i1 1)
+  //   br i1 %expval, label %if.then, label %if.end
+
+  CallInst *CI;
 
   ICmpInst *CmpI = dyn_cast<ICmpInst>(BI->getCondition());
-  if (!CmpI || CmpI->getPredicate() != CmpInst::ICMP_NE)
-    return false;
+  if (!CmpI) {
+    CI = dyn_cast<CallInst>(BI->getCondition());
+  } else {
+    if (CmpI->getPredicate() != CmpInst::ICMP_NE)
+      return false;
+    CI = dyn_cast<CallInst>(CmpI->getOperand(0));
+  }
 
-  CallInst *CI = dyn_cast<CallInst>(CmpI->getOperand(0));
   if (!CI)
     return false;
 
@@ -127,7 +137,10 @@ bool LowerExpectIntrinsic::HandleIfExpect(BranchInst *BI) {
 
   BI->setMetadata(LLVMContext::MD_prof, Node);
 
-  CmpI->setOperand(0, ArgValue);
+  if (CmpI)
+    CmpI->setOperand(0, ArgValue);
+  else
+    BI->setCondition(ArgValue);
   return true;
 }