https://llvm.org/bugs/show_bug.cgi?id=24572
Bug ID: 24572 Summary: Comment describing isFsqrtCheap is probably wrong Product: new-bugs Version: unspecified Hardware: All OS: All Status: NEW Severity: enhancement Priority: P Component: new bugs Assignee: unassignedb...@nondot.org Reporter: schnet...@gmail.com CC: llvm-bugs@lists.llvm.org Classification: Unclassified Line 221 of include/llvm/Target/TargetLowering.h describes isFsqrtCheap, and says /// Return true if sqrt(x) is as cheap or cheaper than 1 / rsqrt(x) This sounds wrong: When one calculates sqrt(x) via rsqrt(x), one does not use 1/rsqrt(x) -- rather, one uses x*rsqrt(x). I did not check what code LLVM generates in this case, but I assume it does not use a division. -- You are receiving this mail because: You are on the CC list for the bug.
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