[Bug 1837522] Re: GCC Miscompilation of vector shift

[Matthias Klose]

the fix for GCC 6 may be not needed, as it's not the default compiler in
any supported release. However GCC 5 needs the fix for 18.06 LTS.


** Also affects: gcc-6 (Ubuntu)
   Importance: Undecided
       Status: New

** Also affects: gcc-5 (Ubuntu)
   Importance: Undecided
       Status: New

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to gcc-7 in Ubuntu.
https://bugs.launchpad.net/bugs/1837522

Title:
  GCC Miscompilation of vector shift

Status in Ubuntu on IBM z Systems:
  Triaged
Status in gcc-5 package in Ubuntu:
  New
Status in gcc-6 package in Ubuntu:
  New
Status in gcc-7 package in Ubuntu:
  New
Status in gcc-8 package in Ubuntu:
  New

Bug description:
  Vector shift miscompilation
   
  ---Steps to Reproduce---
     t.c:
  __vector int
  foo (__vector int a, int s)
  {
    return a << (s + 3);
  }

  gcc -O3 -march=z13 t.c -S -mzvector

  foo:
          veslf   %v24,%v24,0(%r2)   <---- +3 is omitted
          br      %r14
   
  Contact Information = andreas.krebbel at de.ibm.com 
   
  Userspace tool common name: GCC 
   
  The userspace tool has the following bit modes: 64 

  Backported fix has been applied to GCC 8 branch as r273493:

  https://gcc.gnu.org/viewcvs?rev=273493&root=gcc&view=rev

  S/390: Fix vector shift count operand

  We currently use subst definitions to handle the different variants of shift
  count operands. Unfortunately, in the vector shift pattern the shift count
  operand is used directly. Without it being adjusted for the 'subst' variants the
  displacement value is omitted resulting in a wrong shift count being applied.

  This patch needs to be applied to older branches as well.

  gcc/ChangeLog:

  2019-07-15  Andreas Krebbel  <krebbel at linux.ibm.com>

  Backport from mainline
  2019-07-01  Andreas Krebbel  <krebbel at linux.ibm.com>

  * config/s390/vector.md: Fix shift count operand printing.

  gcc/testsuite/ChangeLog:

  2019-07-15  Andreas Krebbel  <krebbel at linux.ibm.com>

  Backport from mainline
  2019-07-01  Andreas Krebbel  <krebbel at linux.ibm.com>

  * gcc.target/s390/vector/vec-shift-2.c: New test.

  Added:
  branches/gcc-8-branch/gcc/testsuite/gcc.target/s390/vector/vec-shift-2.c
  Modified:
  branches/gcc-8-branch/gcc/ChangeLog
  branches/gcc-8-branch/gcc/config/s390/vector.md
  branches/gcc-8-branch/gcc/testsuite/ChangeLog

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu-z-systems/+bug/1837522/+subscriptions