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From: "652023330028 at smail dot nju.edu.cn" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/113265] New: [Regression] Missed optimization for redundancy computation elimination may be due to constant propagation about 0 too late Date: Mon, 08 Jan 2024 08:25:40 +0000 [thread overview] Message-ID: <bug-113265-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113265 Bug ID: 113265 Summary: [Regression] Missed optimization for redundancy computation elimination may be due to constant propagation about 0 too late Product: gcc Version: 14.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: 652023330028 at smail dot nju.edu.cn Target Milestone: --- Hello, we noticed that maybe there is a missed optimization for redundancy computation elimination. https://godbolt.org/z/drfejE5cP int x,y,z; void func(int a, int b){ a=b-x; b=a; y=0; z=(y+a)/(-b); } GCC -O3 : func(int, int): mov ecx, DWORD PTR x[rip] mov eax, esi mov DWORD PTR y[rip], 0 sub eax, ecx sub ecx, esi cdq idiv ecx mov DWORD PTR z[rip], eax ret Earlier GCC versions get the expected optimizations: Expected code (GCC 7.5): func(int, int): mov DWORD PTR y[rip], 0 mov DWORD PTR z[rip], -1 ret The following code is optimized by gcc as expected: void func2(int a, int b){ a=b-x; b=a; y=0; z=(0+a)/(-b); } Comparing the code for func and func2 and their ccp1(tree), we suspect that this issue may be caused by too late propagation about y=0. Thank you very much for your time and effort! We look forward to hearing from you
next reply other threads:[~2024-01-08 8:25 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2024-01-08 8:25 652023330028 at smail dot nju.edu.cn [this message] 2024-01-09 8:06 ` [Bug tree-optimization/113265] " rguenth at gcc dot gnu.org 2024-01-09 8:16 ` rguenth at gcc dot gnu.org 2024-01-09 8:43 ` pinskia at gcc dot gnu.org 2024-01-09 22:55 ` [Bug tree-optimization/113265] [11/12/13/14 Regression] " pinskia at gcc dot gnu.org 2024-01-09 23:01 ` pinskia at gcc dot gnu.org 2024-03-07 20:52 ` law at gcc dot gnu.org 2024-05-26 5:43 ` [Bug tree-optimization/113265] [11/12/13/14/15 " pinskia at gcc dot gnu.org 2024-05-26 5:44 ` pinskia at gcc dot gnu.org
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