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Bug 1645400 - gcc miscompiles bitset code in mesa
Summary: gcc miscompiles bitset code in mesa
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Fedora
Classification: Fedora
Component: gcc
Version: 28
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: ---
Assignee: Jakub Jelinek
QA Contact: Fedora Extras Quality Assurance
URL:
Whiteboard:
: 1645850 (view as bug list)
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2018-11-02 07:11 UTC by Dave Airlie
Modified: 2018-11-10 03:29 UTC (History)
16 users (show)

Fixed In Version: gcc-8.2.1-5.fc29 gcc-8.2.1-5.fc28
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed: 2018-11-09 06:03:27 UTC
Type: Bug
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
GNU Compiler Collection 87859 0 P1 RESOLVED store-merging miscompilation of mesa 2020-09-25 05:34:42 UTC
Red Hat Bugzilla 1646150 0 unspecified CLOSED mesa 18.2.3 update breaks accelerated compositing in WebKitGTK+, many webpages fail to display 2022-05-16 11:32:56 UTC

Internal Links: 1646150

Description Dave Airlie 2018-11-02 07:11:56 UTC 
Description of problem:

Some recent gcc push (at least 8.2.1 is broken, 8.0.1 seems okay) I can bisect further next week, breaks mesa compilation of a bunch of bitfields.

Broken asm:


   input_layout_mask.flags.q.precise = 1;
   input_layout_mask.flags.q.sample = 1;
   input_layout_mask.flags.q.smooth = 1;
   input_layout_mask.flags.q.non_coherent = 1;

   if (state->has_bindless()) {
     203:       80 ba d6 02 00 00 00    cmpb   $0x0,0x2d6(%rdx)
     20a:       48 c7 44 24 40 00 00    movq   $0x60000000,0x40(%rsp)
     211:       00 60 
     213:       c7 44 24 48 00 00 00    movl   $0x0,0x48(%rsp)
     21a:       00 
     21b:       c7 84 24 10 01 00 00    movl   $0x1e000000,0x110(%rsp)
     222:       00 00 00 1e 
     226:       c7 84 24 e0 01 00 00    movl   $0xc00000,0x1e0(%rsp)
     22d:       00 00 c0 00 
     231:       c7 84 24 b4 02 00 00    movl   $0x2000,0x2b4(%rsp)
     238:       00 20 00 00 
     23c:       48 c7 84 24 80 03 00    movq   $0x2840a5,0x380(%rsp)
     243:       00 a5 40 28 00 

Original asm:

     203:       80 ba d6 02 00 00 00    cmpb   $0x0,0x2d6(%rdx)
     20a:       48 c7 44 24 40 00 00    movq   $0x60000000,0x40(%rsp)
     211:       00 60 
     213:       c7 44 24 48 00 00 00    movl   $0x0,0x48(%rsp)
     21a:       00 
     21b:       c7 84 24 10 01 00 00    movl   $0x1e000000,0x110(%rsp)
     222:       00 00 00 1e 
     226:       c7 84 24 e0 01 00 00    movl   $0xc00000,0x1e0(%rsp)
     22d:       00 00 c0 00 
     231:       c7 84 24 b4 02 00 00    movl   $0x2000,0x2b4(%rsp)
     238:       00 20 00 00 
     23c:       48 c7 84 24 80 03 00    movq   $0x2be3e7,0x380(%rsp)
     243:       00 e7 e3 2b 00 

Note the change in 23c movq value.

The code in question is 

https://gitlab.freedesktop.org/mesa/mesa/blob/master/src/compiler/glsl/ast_type.cpp#L254

I intend to dig a bit more next week, but I'd thought I'd at least give a headsup and file a bug.
Comment 1 Jakub Jelinek 2018-11-02 07:40:22 UTC 
8.2.1-whatexactly vs. 8.0.1-whatexactly?
Can you please provide a preprocessed source + full gcc/g++ command line for the corresponding file?
Comment 2 Jakub Jelinek 2018-11-02 07:46:52 UTC 
Note, as a workaround most likely -fno-store-merging should work.
Comment 3 Jakub Jelinek 2018-11-02 08:26:42 UTC 
Actually, reproduced it myself even without preprocessed source:

struct S {
  union F {
    struct T {
#define A(n) unsigned n:1;
#define B(n) A(n##0) A(n##1) A(n##2) A(n##3) A(n##4) A(n##5) A(n##6) A(n##7) A(n##8) A(n##9)
      B(f) B(f1) B(f2) B(f3) B(f4) B(f5) A(f60) A(f61) A(f62) A(f63) A(f64) A(f65) A(f66)
    } q;
    unsigned int i[3];
  } f;
};

__attribute__((noipa)) void
bar (unsigned *x)
{
  if (x[0] != 0x002be3e7)
    __builtin_abort ();
}

__attribute__((noipa)) void
foo (unsigned char *state)
{
  struct S i;
  i.f.i[0] = 0; i.f.i[1] = 0; i.f.i[2] = 0; i.f.q.f7 = 1; i.f.q.f2 = 1; i.f.q.f21 = 1;
  i.f.q.f19 = 1; i.f.q.f14 = 1; i.f.q.f5 = 1; i.f.q.f0 = 1; i.f.q.f15 = 1; i.f.q.f16 = 1;
  i.f.q.f6 = 1; i.f.q.f9 = 1; i.f.q.f17 = 1; i.f.q.f1 = 1; i.f.q.f8 = 1; i.f.q.f13 = 1;
  i.f.q.f66 = 1;
  if (*state)
    {
      i.f.q.f37 = 1; i.f.q.f38 = 1; i.f.q.f39 = 1; i.f.q.f40 = 1; i.f.q.f41 = 1; i.f.q.f36 = 1;
    }
  bar (i.f.i);
}

int
main ()
{
  unsigned char zero = 0;
  foo (&zero);
  return 0;
}
Comment 4 Jakub Jelinek 2018-11-02 08:31:37 UTC 
Started with my http://gcc.gnu.org/r264232 .
Comment 5 Jakub Jelinek 2018-11-05 10:44:47 UTC 
*** Bug 1645850 has been marked as a duplicate of this bug. ***
Comment 6 Jakub Jelinek 2018-11-05 18:50:40 UTC 
gcc-8.2.1-5.fc{28,29,30} which should fix this is building in koji.
Comment 7 Michael Catanzaro 2018-11-05 19:22:30 UTC 
Igor, maybe you could get a buildroot override to speed up the process of releasing a fixed mesa?
Comment 8 Jakub Jelinek 2018-11-05 19:30:45 UTC 
Because arm 32-bit is extremely slow, the gcc builds usually take a day or so, so should finish probably tomorrow noon in Europe or so.
Comment 9 Jakub Jelinek 2018-11-05 19:31:56 UTC 
That said, f29 x86_64 rpm is built, so if somebody wants to test it out outside of koji, it is possible manually:
https://koji.fedoraproject.org/koji/taskinfo?taskID=30689762
Comment 10 Jakub Jelinek 2018-11-06 12:00:45 UTC 
gcc-8.2.1-5.fc{28,29,30} built fine, is in f30 now, before filing bodhi erratas for f28/f29 I'd like to hear that it actually resolved the mesa issues.  Can anyone please verify that?
Comment 11 Robert-André Mauchin 🐧 2018-11-06 16:03:03 UTC 
Recompiled Mesa 18.2.4 locally with this new GCC and the bug #1645850 is solved. Playback with mpv is fine and without shaders issues anymore.
Comment 12 Fedora Update System 2018-11-06 23:36:58 UTC 
gcc-8.2.1-5.fc29 has been submitted as an update to Fedora 29. https://bodhi.fedoraproject.org/updates/FEDORA-2018-de93530d49
Comment 13 Fedora Update System 2018-11-06 23:37:37 UTC 
gcc-8.2.1-5.fc28 has been submitted as an update to Fedora 28. https://bodhi.fedoraproject.org/updates/FEDORA-2018-cd24e05681
Comment 14 Fedora Update System 2018-11-07 04:13:53 UTC 
gcc-8.2.1-5.fc29 has been pushed to the Fedora 29 testing repository. If problems still persist, please make note of it in this bug report.
See https://fedoraproject.org/wiki/QA:Updates_Testing for
instructions on how to install test updates.
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2018-de93530d49
Comment 15 Fedora Update System 2018-11-07 04:25:17 UTC 
gcc-8.2.1-5.fc28 has been pushed to the Fedora 28 testing repository. If problems still persist, please make note of it in this bug report.
See https://fedoraproject.org/wiki/QA:Updates_Testing for
instructions on how to install test updates.
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2018-cd24e05681
Comment 16 Fedora Update System 2018-11-09 06:03:27 UTC 
gcc-8.2.1-5.fc29 has been pushed to the Fedora 29 stable repository. If problems still persist, please make note of it in this bug report.
Comment 17 Fedora Update System 2018-11-10 03:29:28 UTC 
gcc-8.2.1-5.fc28 has been pushed to the Fedora 28 stable repository. If problems still persist, please make note of it in this bug report.
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