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From: "llvm at rifkin dot dev" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/103559] New: Can't optimize away < 0 check on sqrt Date: Sat, 04 Dec 2021 20:58:21 +0000 [thread overview] Message-ID: <bug-103559-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103559 Bug ID: 103559 Summary: Can't optimize away < 0 check on sqrt Product: gcc Version: 12.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: llvm at rifkin dot dev Target Milestone: --- For a simple invocation of sqrt, gcc inserts a < 0 check to set math errno if needed. E.g. float f(float x) { return sqrt(x); } Is generated as f(float): vxorps xmm1, xmm1, xmm1 vucomiss xmm1, xmm0 ja .L10 vsqrtss xmm0, xmm0, xmm0 ret .L10: jmp sqrtf Unfortunately, this check is still present when the GCC is able to prove that x is non-negative: float f(float x) { if(x < 0) [[unlikely]] { __builtin_unreachable(); } else { return sqrt(x); } } LLVM suffers from the same problem, even with __builtin_assume(). https://godbolt.org/z/ddcoMj3oz This is a very common pattern, and I'd imagine the argument for sqrt is often able to be shown to be positive. This would be a helpful enhancement.
next reply other threads:[~2021-12-04 20:58 UTC|newest] Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-12-04 20:58 llvm at rifkin dot dev [this message] 2021-12-04 21:01 ` [Bug tree-optimization/103559] " pinskia at gcc dot gnu.org 2021-12-04 21:34 ` pinskia at gcc dot gnu.org 2021-12-04 21:38 ` pinskia at gcc dot gnu.org 2021-12-04 21:43 ` pinskia at gcc dot gnu.org 2021-12-05 11:38 ` vanyacpp at gmail dot com 2023-03-29 17:46 ` aldyh at gcc dot gnu.org 2023-03-29 18:34 ` llvm at rifkin dot dev 2023-03-29 18:39 ` jakub at gcc dot gnu.org 2023-03-30 10:40 ` xry111 at gcc dot gnu.org 2023-03-30 10:48 ` jakub at gcc dot gnu.org 2023-03-30 10:53 ` xry111 at gcc dot gnu.org 2023-03-30 11:41 ` jakub at gcc dot gnu.org
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