[Bug target/94557] New: [9 regression] r9-8486 causes several builtin instruction test case execution failures on power 9

[Bug target/94557] New: [9 regression] r9-8486 causes several builtin instruction test case execution failures on power 9

[seurer at linux dot vnet.ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94557

            Bug ID: 94557
           Summary: [9 regression] r9-8486 causes several builtin
                    instruction test case execution failures on power 9
           Product: gcc
           Version: 9.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: seurer at linux dot vnet.ibm.com
  Target Milestone: ---

g:892c755eae2e2e45547395013695fdd819c297fa, r9-8486

FAIL: gcc.target/powerpc/vsx-builtin-10b.c execution test
FAIL: gcc.target/powerpc/vsx-builtin-11b.c execution test
FAIL: gcc.target/powerpc/vsx-builtin-16b.c execution test
FAIL: gcc.target/powerpc/vsx-builtin-17b.c execution test
FAIL: gcc.target/powerpc/vsx-builtin-18b.c execution test
FAIL: gcc.target/powerpc/vsx-builtin-9b.c execution test

[Bug target/94557] [9 regression] r9-8486 causes several builtin instruction test case execution failures on power 9

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94557

--- Comment #1 from Michael Meissner <meissner at gcc dot gnu.org> ---
Created attachment 48263
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48263&action=edit
Proposed patch to fix the problem.

This patch backports a necessary fix from the trunk to fix the problem.

[Bug target/94557] [9 regression] r9-8486 causes several builtin instruction test case execution failures on power 9

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94557

Michael Meissner <meissner at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2020-04-13

--- Comment #2 from Michael Meissner <meissner at gcc dot gnu.org> ---
The issue is that with the backport patch for PR target/93932, GCC is more
likely to optimize variable extracts from a vector that is in memory to be a
simple load, instead of loading the vector into a vector register, and doing a
vector extract on power9.

The test cases rely on having indexes outside of the range of valid indexes. 
If the vector was loaded into a register, we would automatically mask the index
as part of the extract.

However, if we converted the operation to a single load, we did not do the
masking, and the load would load some random value outside of the vector
boundary.

The trunk had previously had other changes that did this masking as part of the
changes for -mcpu=future and PC-relative support.  The proposed patch just
makes sure the index is properly masked before it is used.

[Bug target/94557] [9 regression] r9-8486 causes several builtin instruction test case execution failures on power 9

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94557

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |9.4
      Known to work|                            |9.3.0
           Priority|P3                          |P1

[Bug target/94557] [9 regression] r9-8486 causes several builtin instruction test case execution failures on power 9

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94557

--- Comment #3 from Michael Meissner <meissner at gcc dot gnu.org> ---
Just to be clear, this bug are only bugs in the GCC 9 branch, and it came about
due to the back port of the patch for PR target/93932 to the GCC 9 branch.  The
master branch generates correct code.  So, I'm not sure this warrants being a
P1 blocker for the GCC 10 release.

[Bug target/94557] [9 regression] r9-8486 causes several builtin instruction test case execution failures on power 9

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94557

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-9 branch has been updated by Michael Meissner
<meissner@gcc.gnu.org>:

https://gcc.gnu.org/g:baf3a5a94244b4a260810825870be6ecc15fa35a

commit r9-8504-gbaf3a5a94244b4a260810825870be6ecc15fa35a
Author: Michael Meissner <2019-02-12  Michael Meissner  meissner@linux.ibm.com>
Date:   Thu Apr 16 12:49:22 2020 -0400

    Fix target/94557 PowerPC regression on GCC 9 (variable vec_extract)

    2020-04-16  Michael Meissner  <meissner@linux.ibm.com>

            PR target/94557
            * config/rs6000/rs6000.c (rs6000_adjust_vec_address): Fix
            regression caused by PR target/93932 backport.  Mask variable
            vector extract index so it does not go beyond the vector when
            extracting a vector element from memory.

[Bug target/94557] [9 regression] r9-8486 causes several builtin instruction test case execution failures on power 9

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94557

Michael Meissner <meissner at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #5 from Michael Meissner <meissner at gcc dot gnu.org> ---
Fixed by a change to GCC 9 on April 16th, 2020.