[llvm] [slp][profcheck] Mark `select`s as having unknown profile (PR #162960)

[Mircea Trofin via llvm-commits]

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@@ -1002,6 +1003,18 @@ CallInst *IRBuilderBase::CreateConstrainedFPCall(
   return C;
 }
 
+Value *IRBuilderBase::CreateSelectWithUnknownProfile(Value *C, Value *True,
+                                                     Value *False,
+                                                     StringRef PassName,
+                                                     const Twine &Name) {
+  Value *Ret = CreateSelectFMF(C, True, False, {}, Name);
+  if (auto *SI = dyn_cast<SelectInst>(Ret)) {
+    setExplicitlyUnknownBranchWeightsIfProfiled(
+        *SI, *SI->getParent()->getParent(), PassName);
+  }
+  return Ret;
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mtrofin wrote:

Ack. 

FWIW, I'm actively thinking how to avoid the explicit name and still get the property we want - namely, identification of origin of "unknowns", which we can use to farm out opportunities for better profiling. If there aren't too many cases, maybe it's not too bad, but I want to have an alternative ready.

https://github.com/llvm/llvm-project/pull/162960