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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/95383] Poor codegen when constructing a trivial Optional Date: Fri, 29 May 2020 06:21:01 +0000 [thread overview] Message-ID: <bug-95383-4-XcIU5NuTIx@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-95383-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95383 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |jamborm at gcc dot gnu.org, | |rguenth at gcc dot gnu.org Keywords| |missed-optimization Last reconfirmed| |2020-05-29 Status|UNCONFIRMED |NEW Ever confirmed|0 |1 --- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> --- I see the cited -O3 code-gen with -O2 on trunk. We expand from foo (bool b) { struct Optional D.2251; unsigned char _7; <bb 2> [local count: 1073741824]: if (b_2(D) != 0) goto <bb 3>; [50.00%] else goto <bb 4>; [50.00%] <bb 3> [local count: 536870913]: D.2251.D.2152.value = 42; <bb 4> [local count: 1073741824]: # _7 = PHI <1(3), 0(2)> MEM <unsigned char> [(struct Optional *)&D.2251 + 4B] = _7; return D.2251; where the main issue is likely we fail to elide D.2251 because of the aggregate return (and us not exposing the ABI, etc.). Note above D.2251 is partly initialized which makes it a bit more difficult to optimize. SRA might try to handle these cases by rematerializing the aggregate just before the return. We can then hope for RTL expansion to do "magic".
next prev parent reply other threads:[~2020-05-29 6:21 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-05-28 13:56 [Bug c++/95383] New: " barry.revzin at gmail dot com 2020-05-29 6:21 ` rguenth at gcc dot gnu.org [this message] 2021-12-17 5:33 ` [Bug middle-end/95383] " pinskia at gcc dot gnu.org 2023-07-12 21:35 ` pinskia at gcc dot gnu.org
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