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* [Bug rtl-optimization/114688] New: repeat load argument of an inline function @ 2024-04-11 6:56 absoler at smail dot nju.edu.cn 2024-04-11 7:06 ` [Bug rtl-optimization/114688] " rguenth at gcc dot gnu.org 2024-04-11 7:07 ` pinskia at gcc dot gnu.org 0 siblings, 2 replies; 3+ messages in thread From: absoler at smail dot nju.edu.cn @ 2024-04-11 6:56 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114688 Bug ID: 114688 Summary: repeat load argument of an inline function Product: gcc Version: 13.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: rtl-optimization Assignee: unassigned at gcc dot gnu.org Reporter: absoler at smail dot nju.edu.cn Target Milestone: --- Hi, here's the case, regression from gcc-10, x86-64 ``` char g; int v; void foo(char p_17); void func_1() { foo(g); } void foo(char c) { v = (char)(2 - c) & c; } ``` -O2 produce this for `func_1`: ``` <func_1>: foo(): 401130: mov $0x2,%eax 401135: sub 0x2ef5(%rip),%al # 404030 <g> 40113b: and 0x2eef(%rip),%al # 404030 <g> 401141: movsbl %al,%eax 401144: mov %eax,0x2ee2(%rip) # 40402c <v> func_1(): 40114a: retq ``` it seems register allocator feels it's better to repeat load `g` instead of generating an extra `mov` to load it. while clang-trunk choose to do so: https://godbolt.org/z/bqxz8fMYn ^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug rtl-optimization/114688] repeat load argument of an inline function 2024-04-11 6:56 [Bug rtl-optimization/114688] New: repeat load argument of an inline function absoler at smail dot nju.edu.cn @ 2024-04-11 7:06 ` rguenth at gcc dot gnu.org 2024-04-11 7:07 ` pinskia at gcc dot gnu.org 1 sibling, 0 replies; 3+ messages in thread From: rguenth at gcc dot gnu.org @ 2024-04-11 7:06 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114688 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Last reconfirmed| |2024-04-11 Keywords| |missed-optimization, ra Ever confirmed|0 |1 Target| |x86_64-*-* Status|UNCONFIRMED |NEW --- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> --- char g; int v; static inline __attribute__((always_inline)) void foo(char p_17); void func_1() { foo(g); } static inline void foo(char c) { v = (char)(2 - c) & c; } shows that with -Os we get func_1: .LFB0: .cfi_startproc movb g(%rip), %dl movb $2, %al subl %edx, %eax andl %edx, %eax movsbl %al, %eax movl %eax, v(%rip) ret I think we have duplicate bugs that show we're too happy replicating memory operands to multiple instructions. That might be a target cost thing in the end. ^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug rtl-optimization/114688] repeat load argument of an inline function 2024-04-11 6:56 [Bug rtl-optimization/114688] New: repeat load argument of an inline function absoler at smail dot nju.edu.cn 2024-04-11 7:06 ` [Bug rtl-optimization/114688] " rguenth at gcc dot gnu.org @ 2024-04-11 7:07 ` pinskia at gcc dot gnu.org 1 sibling, 0 replies; 3+ messages in thread From: pinskia at gcc dot gnu.org @ 2024-04-11 7:07 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114688 --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114591#c13 is talking about this exact thing ... So this might be expected for x86_64. ^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2024-04-11 7:07 UTC | newest] Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2024-04-11 6:56 [Bug rtl-optimization/114688] New: repeat load argument of an inline function absoler at smail dot nju.edu.cn 2024-04-11 7:06 ` [Bug rtl-optimization/114688] " rguenth at gcc dot gnu.org 2024-04-11 7:07 ` pinskia at gcc dot gnu.org
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