[PATCH] D79830: Add support of __builtin_expect_with_probability

[Zhi Zhuang via Phabricator via cfe-commits]

LukeZhuang added inline comments.


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Comment at: clang/lib/Sema/SemaChecking.cpp:1805
+    const Expr *ProbArg = TheCall->getArg(2);
+    if (ProbArg->EvaluateAsFloat(Confidence, Context)) {
+      double P = Confidence.convertToDouble();
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LukeZhuang wrote:
> rsmith wrote:
> > What rules should be applied here? Do we just want to allow anything that we can evaluate (which might change over time), or do we want to use the underlying language's notion of floating-point constant expressions, if it has them?
> Thank you for commenting. I just read the llvm::Expr document and found that it just have `isIntegerConstantExpr` without a float-point version. Under `EvaluateAsFloat` it says "Return true if this is a constant which we can fold and convert to a floating point value", thus I use this function. Is there any better function to achieve this goal?
Hi, and I didn't find other builtin functions ever handle case like this, is there any example I could refer to?


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  https://reviews.llvm.org/D79830/new/

https://reviews.llvm.org/D79830