[Bug 1856682] Re: GCC Miscompilation in vectorized code

Wed Jan 29 22:57:39 UTC 2020

Launchpad has imported 4 comments from the remote bug at
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92950.

If you reply to an imported comment from within Launchpad, your comment
will be sent to the remote bug automatically. Read more about
Launchpad's inter-bugtracker facilities at
https://help.launchpad.net/InterBugTracking.

------------------------------------------------------------------------
On 2019-12-16T07:51:59+00:00 Krebbel wrote:

The following testcase abort when being compiled with -O3 -march=z13 on
IBM Z:

struct a {
  int b;
  char c;
};
struct a d = {1, 16};
struct a *e = &d;

int f = 0;

int main() {
  struct a g = {0, 0 };
  f = 0;

  for (; f <= 1; f++) {
    g = d;
    *e = g;
  }

  if (d.c != 16)
    __builtin_abort();
}

The movv1qi pattern emits halfword load instructions instead of
character loads.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/gcc-9/+bug/1856682/comments/0

------------------------------------------------------------------------
On 2019-12-16T08:04:00+00:00 Krebbel wrote:

Author: krebbel
Date: Mon Dec 16 08:03:28 2019
New Revision: 279410

URL: https://gcc.gnu.org/viewcvs?rev=279410&root=gcc&view=rev
Log:
Fix PR92950: Wrong code emitted for movv1qi

The backend emits 16 bit memory loads for single element character
vector.  As a result the character will not be right justified in the
GPR.

gcc/ChangeLog:

2019-12-16  Andreas Krebbel  <krebbel at linux.ibm.com>

	PR target/92950
	* config/s390/vector.md ("mov<mode>" for V_8): Replace lh, lhy,
	and lhrl with llc.

gcc/testsuite/ChangeLog:

2019-12-16  Andreas Krebbel  <krebbel at linux.ibm.com>

	PR target/92950
	* gcc.target/s390/vector/pr92950.c: New test.

Added:
    trunk/gcc/testsuite/gcc.target/s390/vector/pr92950.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/s390/vector.md
    trunk/gcc/testsuite/ChangeLog

Reply at:
https://bugs.launchpad.net/ubuntu/+source/gcc-9/+bug/1856682/comments/1

------------------------------------------------------------------------
On 2019-12-17T08:38:02+00:00 Krebbel wrote:

Author: krebbel
Date: Tue Dec 17 08:37:26 2019
New Revision: 279453

URL: https://gcc.gnu.org/viewcvs?rev=279453&root=gcc&view=rev
Log:
Fix PR92950: Wrong code emitted for movv1qi

The backend emits 16 bit memory loads for single element character
vector.  As a result the character will not be right justified in the
GPR.

gcc/ChangeLog:

2019-12-17  Andreas Krebbel  <krebbel at linux.ibm.com>

	Backport from mainline
	2019-12-16  Andreas Krebbel  <krebbel at linux.ibm.com>

	PR target/92950
	* config/s390/vector.md ("mov<mode>" for V_8): Replace lh, lhy,
	and lhrl with llc.

gcc/testsuite/ChangeLog:

2019-12-17  Andreas Krebbel  <krebbel at linux.ibm.com>

	Backport from mainline
	2019-12-16  Andreas Krebbel  <krebbel at linux.ibm.com>

	PR target/92950
	* gcc.target/s390/vector/pr92950.c: New test.

Added:
    branches/gcc-9-branch/gcc/testsuite/gcc.target/s390/vector/pr92950.c
Modified:
    branches/gcc-9-branch/gcc/ChangeLog
    branches/gcc-9-branch/gcc/config/s390/vector.md
    branches/gcc-9-branch/gcc/testsuite/ChangeLog

Reply at:
https://bugs.launchpad.net/ubuntu/+source/gcc-9/+bug/1856682/comments/2

------------------------------------------------------------------------
On 2019-12-17T08:42:26+00:00 Krebbel wrote:

Author: krebbel
Date: Tue Dec 17 08:41:54 2019
New Revision: 279454

URL: https://gcc.gnu.org/viewcvs?rev=279454&root=gcc&view=rev
Log:
Fix PR92950: Wrong code emitted for movv1qi

The backend emits 16 bit memory loads for single element character
vector.  As a result the character will not be right justified in the
GPR.

gcc/ChangeLog:

2019-12-17  Andreas Krebbel  <krebbel at linux.ibm.com>

	Backport from mainline
	2019-12-16  Andreas Krebbel  <krebbel at linux.ibm.com>

	PR target/92950
	* config/s390/vector.md ("mov<mode>" for V_8): Replace lh, lhy,
	and lhrl with llc.

gcc/testsuite/ChangeLog:

2019-12-17  Andreas Krebbel  <krebbel at linux.ibm.com>

	Backport from mainline
	2019-12-16  Andreas Krebbel  <krebbel at linux.ibm.com>

	PR target/92950
	* gcc.target/s390/vector/pr92950.c: New test.

Added:
    branches/gcc-8-branch/gcc/testsuite/gcc.target/s390/vector/pr92950.c
Modified:
    branches/gcc-8-branch/gcc/ChangeLog
    branches/gcc-8-branch/gcc/config/s390/vector.md
    branches/gcc-8-branch/gcc/testsuite/ChangeLog

Reply at:
https://bugs.launchpad.net/ubuntu/+source/gcc-9/+bug/1856682/comments/3

** Changed in: gcc
       Status: Unknown => New

** Changed in: gcc
   Importance: Unknown => High

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to gcc-8 in Ubuntu.
https://bugs.launchpad.net/bugs/1856682

Title:
  GCC Miscompilation in vectorized code

Status in gcc:
  New
Status in Ubuntu on IBM z Systems:
  Triaged
Status in gcc-5 package in Ubuntu:
  Invalid
Status in gcc-6 package in Ubuntu:
  Invalid
Status in gcc-7 package in Ubuntu:
  New
Status in gcc-8 package in Ubuntu:
  New
Status in gcc-9 package in Ubuntu:
  Fix Released
Status in gcc-5 source package in Xenial:
  New
Status in gcc-6 source package in Xenial:
  Invalid
Status in gcc-7 source package in Xenial:
  Invalid
Status in gcc-8 source package in Xenial:
  Invalid
Status in gcc-9 source package in Xenial:
  Invalid
Status in gcc-5 source package in Bionic:
  New
Status in gcc-6 source package in Bionic:
  New
Status in gcc-7 source package in Bionic:
  New
Status in gcc-8 source package in Bionic:
  New
Status in gcc-9 source package in Bionic:
  Invalid
Status in gcc-5 source package in Disco:
  Invalid
Status in gcc-6 source package in Disco:
  New
Status in gcc-7 source package in Disco:
  New
Status in gcc-8 source package in Disco:
  New
Status in gcc-9 source package in Disco:
  New
Status in gcc-5 source package in Eoan:
  Invalid
Status in gcc-6 source package in Eoan:
  Invalid
Status in gcc-7 source package in Eoan:
  New
Status in gcc-8 source package in Eoan:
  New
Status in gcc-9 source package in Eoan:
  New
Status in gcc-5 source package in Focal:
  Invalid
Status in gcc-6 source package in Focal:
  Invalid
Status in gcc-7 source package in Focal:
  New
Status in gcc-8 source package in Focal:
  New
Status in gcc-9 source package in Focal:
  Fix Released

Bug description:
  Miscompilation in autovectorized code.

  ---Steps to Reproduce---
   See GCC BZ: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92950

  The following testcase abort when being compiled with -O3 -march=z13
  on IBM Z:

  struct a {
    int b;
    char c;
  };
  struct a d = {1, 16};
  struct a *e = &d;

  int f = 0;

  int main() {
    struct a g = {0, 0 };
    f = 0;

    for (; f <= 1; f++) {
      g = d;
      *e = g;
    }

    if (d.c != 16)
      __builtin_abort();
  }

  The movv1qi pattern emits halfword load instructions instead of character
  loads.

  All GCC versions since GCC 5 are affected.
  Patches for GCC 8, 9, and 10 have been committed to the gcc.gnu.org branches.

  Userspace tool common name: gcc  
  The userspace tool has the following bit modes: 64 
  Userspace rpm: various Ubuntu gcc packages

  Package need to updated within LP

To manage notifications about this bug go to:
https://bugs.launchpad.net/gcc/+bug/1856682/+subscriptions