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From: "antoshkka at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/110170] New: Sub-optimal conditional jumps in conditional-swap with floating point Date: Thu, 08 Jun 2023 11:31:05 +0000 [thread overview] Message-ID: <bug-110170-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110170 Bug ID: 110170 Summary: Sub-optimal conditional jumps in conditional-swap with floating point Product: gcc Version: 14.0 Status: UNCONFIRMED Keywords: missed-optimization Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: antoshkka at gmail dot com Target Milestone: --- Some of the C++ algorithms are written in attempt to avoid conditional jumps in tight loops. For example, code close the following could be seen in libc++: void __cond_swap(double* __x, double* __y) { bool __r = (*__x < *__y); auto __tmp = __r ? *__x : *__y; *__y = __r ? *__y : *__x; *__x = __tmp; } GCC-14 with -O2 and -march=x86-64 options generates the following code: __cond_swap(double*, double*): movsd xmm1, QWORD PTR [rdi] movsd xmm0, QWORD PTR [rsi] comisd xmm0, xmm1 jbe .L2 movq rax, xmm1 movapd xmm1, xmm0 movq xmm0, rax .L2: movsd QWORD PTR [rsi], xmm1 movsd QWORD PTR [rdi], xmm0 ret A conditional jump could be probably avoided in the following way: __cond_swap(double*, double*): movsd xmm0, qword ptr [rdi] movsd xmm1, qword ptr [rsi] movapd xmm2, xmm0 minsd xmm2, xmm1 maxsd xmm1, xmm0 movsd qword ptr [rsi], xmm1 movsd qword ptr [rdi], xmm2 ret Playground: https://godbolt.org/z/v3jW67x91
next reply other threads:[~2023-06-08 11:31 UTC|newest] Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-06-08 11:31 antoshkka at gmail dot com [this message] 2023-06-08 11:34 ` [Bug tree-optimization/110170] " pinskia at gcc dot gnu.org 2023-06-08 11:57 ` [Bug target/110170] " antoshkka at gmail dot com 2023-06-08 13:32 ` pinskia at gcc dot gnu.org 2023-06-08 19:40 ` pinskia at gcc dot gnu.org 2023-06-09 5:38 ` crazylht at gmail dot com 2023-06-09 6:40 ` crazylht at gmail dot com 2023-06-09 7:01 ` crazylht at gmail dot com 2023-06-09 7:03 ` rguenth at gcc dot gnu.org 2023-06-12 2:17 ` crazylht at gmail dot com 2023-06-12 9:09 ` crazylht at gmail dot com 2023-07-04 5:46 ` crazylht at gmail dot com 2023-07-06 5:54 ` cvs-commit at gcc dot gnu.org 2023-07-10 1:06 ` cvs-commit at gcc dot gnu.org 2023-07-11 9:51 ` antoshkka at gmail dot com 2023-07-11 13:23 ` crazylht at gmail dot com 2023-07-11 13:57 ` cvs-commit at gcc dot gnu.org 2023-07-18 10:28 ` rguenth at gcc dot gnu.org 2023-07-18 10:33 ` crazylht at gmail dot com 2023-07-18 13:48 ` rguenth at gcc dot gnu.org 2023-07-21 8:18 ` rguenth at gcc dot gnu.org 2023-10-17 6:31 ` cvs-commit at gcc dot gnu.org 2023-10-17 11:14 ` cvs-commit at gcc dot gnu.org 2023-10-26 5:30 ` cvs-commit at gcc dot gnu.org
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