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From: "krystalgamer at protonmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/103882] Register corruption in ASM only functions when optization is -O2/-Os/-O3
Date: Sat, 01 Jan 2022 12:45:06 +0000 [thread overview]
Message-ID: <bug-103882-4-H0VgkvJIW9@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-103882-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103882
--- Comment #6 from Jose Silva <krystalgamer at protonmail dot com> ---
Yes, noipa does help.
(In reply to Andrew Pinski from comment #3)
> Oh that is because there is some IPA Register allocation going on. Anyways
> this is still not a bug. You need to mark a0 as a clobber in the inline-asm
> to let GCC know that a0 is touched.
As I said I simplified the example, the original code had a syscall which I
have no idea which registers will be clobbered.
Before upgrading compilers I was using GCC 3.2 which produces the following
code with `-nostdlib -Os`:
```
a0020060 <test>:
a0020060: 27bdfff0 addiu sp,sp,-16
a0020064: ffb00000 sd s0,0(sp)
a0020068: ffbf0008 sd ra,8(sp)
a002006c: 0c008016 jal a0020058 <fail>
a0020070: 0080802d move s0,a0
a0020074: 0200202d move a0,s0
a0020078: dfbf0008 ld ra,8(sp)
a002007c: dfb00000 ld s0,0(sp)
a0020080: 08008012 j a0020048 <is_first_char_a>
a0020084: 27bd0010 addiu sp,sp,16
```
I'm quite confused on why you say "Anyways this is still not a bug". IPA RA is
making assumptions on procedures where it does not have enough information to
do so, i.e functions with asm statements. It is disabled when a function
pointer is used, why shouldn't it be for when a function with ASM statement is
encountered?
The code inside the `fail()` function is valid and does not break the ABI, GCC
does not have enough information to perform IPA RA but does so(wrongly), to me
that's a bug.
next prev parent reply other threads:[~2022-01-01 12:45 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-31 17:11 [Bug target/103882] New: " krystalgamer at protonmail dot com
2021-12-31 18:53 ` [Bug target/103882] " pinskia at gcc dot gnu.org
2021-12-31 20:48 ` krystalgamer at protonmail dot com
2021-12-31 20:51 ` pinskia at gcc dot gnu.org
2021-12-31 20:51 ` pinskia at gcc dot gnu.org
2021-12-31 22:36 ` jakub at gcc dot gnu.org
2022-01-01 12:45 ` krystalgamer at protonmail dot com [this message]
2022-01-01 14:05 ` jakub at gcc dot gnu.org
2022-01-01 14:11 ` jakub at gcc dot gnu.org
2022-01-01 15:06 ` krystalgamer at protonmail dot com
2022-01-01 16:37 ` jakub at gcc dot gnu.org
2022-01-01 19:19 ` krystalgamer at protonmail dot com
2022-01-01 19:47 ` schwab@linux-m68k.org
2022-01-01 20:34 ` jakub at gcc dot gnu.org
2022-01-01 23:15 ` krystalgamer at protonmail dot com
2022-01-02 13:27 ` jakub at gcc dot gnu.org
2022-01-02 14:40 ` krystalgamer at protonmail dot com
2022-01-02 15:00 ` schwab@linux-m68k.org
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