[Bug target/100108] New: [10 Regression] powerpc: recognize 32-bit CPU as POWER9 with -misel option

[Bug target/100108] New: [10 Regression] powerpc: recognize 32-bit CPU as POWER9 with -misel option

[rin at NetBSD dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100108

            Bug ID: 100108
           Summary: [10 Regression] powerpc: recognize 32-bit CPU as
                    POWER9 with -misel option
           Product: gcc
           Version: 10.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rin at NetBSD dot org
  Target Milestone: ---

Created attachment 50609
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50609&action=edit
Fix for this regression

GCC10 wrongly recognizes CPU as POWER9 if -misel is specified, even when
it is configured for 32-bit processors:

% cat test.c
int main(void)
{
        return 0;
}
% gcc10 -misel -S test.c -o test10.S
% gcc9  -misel -S test.c -o test9.S
% diff -u test9.S test10.S
--- test.9      2021-04-16 10:53:47.116917225 +0900
+++ test.10     2021-04-16 10:53:38.075282430 +0900
@@ -1,5 +1,5 @@
        .file   "test.c"
-       .machine ppc
+       .machine power9
        .section        ".text"
        .align 2
        .globl main
...(snip)...

This is because rs6000_machine_from_flags() assumes ISEL instructions
are supported only by POWER9 and successors. However, ISEL is also
implemented for 32-bit processors like e500.

Please apply the attached patch to fix the problem.

----

% gcc10 -v
Using built-in specs.
COLLECT_GCC=/build/tools.broken/bin/powerpc--netbsd-gcc
COLLECT_LTO_WRAPPER=/build/tools.broken/libexec/gcc/powerpc--netbsd/10.3.0/lto-wrapper
Target: powerpc--netbsd
Configured with: /usr/src/tools/gcc/../../external/gpl3/gcc/dist/configure
--target=powerpc--netbsd --enable-long-long --enable-threads
--with-bugurl=http://www.NetBSD.org/support/send-pr.html
--with-pkgversion='NetBSD nb1 20210411' --with-system-zlib --without-isl
--enable-__cxa_atexit --enable-libstdcxx-time=rt --enable-libstdcxx-threads
--with-diagnostics-color=auto-if-env --with-default-libstdcxx-abi=new
--with-sysroot=/build/dest/evbppc-powerpc --with-mpc=/build/tools.broken
--with-mpfr=/build/tools.broken --with-gmp=/build/tools.broken --disable-nls
--disable-multilib --program-transform-name='s,^,powerpc--netbsd-,'
--enable-languages='c c++ objc' --prefix=/build/tools.broken
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 10.3.0 (NetBSD nb1 20210411)

----

% gcc9 -v
Using built-in specs.
COLLECT_GCC=/build/tools.9/bin/powerpc--netbsd-gcc
COLLECT_LTO_WRAPPER=/build/tools.9/libexec/gcc/powerpc--netbsd/9.3.0/lto-wrapper
Target: powerpc--netbsd
Configured with: /usr/src/tools/gcc/../../external/gpl3/gcc.old/dist/configure
--target=powerpc--netbsd --enable-long-long --enable-threads
--with-bugurl=http://www.NetBSD.org/support/send-pr.html
--with-pkgversion='NetBSD nb1 20200907' --with-system-zlib --without-isl
--enable-__cxa_atexit --enable-libstdcxx-time=rt --enable-libstdcxx-threads
--with-diagnostics-color=auto-if-env --with-default-libstdcxx-abi=new
--with-sysroot=/build/dest/evbppc-powerpc --with-mpc=/build/tools.9
--with-mpfr=/build/tools.9 --with-gmp=/build/tools.9 --disable-nls
--disable-multilib --program-transform-name='s,^,powerpc--netbsd-,'
--enable-languages='c c++ objc' --prefix=/build/tools.9
Thread model: posix
gcc version 9.3.0 (NetBSD nb1 20200907)

[Bug target/100108] [10/11 Regression] powerpc: recognize 32-bit CPU as POWER9 with -misel option

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100108

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |10.4
            Summary|[10 Regression] powerpc:    |[10/11 Regression] powerpc:
                   |recognize 32-bit CPU as     |recognize 32-bit CPU as
                   |POWER9 with -misel option   |POWER9 with -misel option

[Bug target/100108] [10/11 Regression] powerpc: recognize 32-bit CPU as POWER9 with -misel option

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100108

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
e500 support had been moved to the powerpcspe target; so assuming power9 for
-misel is correct.

e500mc support is still there though.

[Bug target/100108] [10/11 Regression] powerpc: recognize 32-bit CPU as POWER9 with -misel option

[rin at NetBSD dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100108

--- Comment #2 from Rin Okuyama <rin at NetBSD dot org> ---
e500mc also supports isel. See its reference manual (Sec. 3.4.5.3):

https://www.nxp.com/docs/en/reference-manual/E500MCRM.pdf

or source code of binutils/gas:

https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=gas/config/tc-ppc.c;h=c719b408b0eb59357f6d7e7022a9d041e181c318;hb=HEAD#l3973

[Bug target/100108] [10/11 Regression] powerpc: recognize 32-bit CPU as POWER9 with -misel option

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100108

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dje at gcc dot gnu.org,
                   |                            |jakub at gcc dot gnu.org,
                   |                            |segher at gcc dot gnu.org

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Indeed, several rs6000-cpus.def entries have MASK_ISEL:
RS6000_CPU ("8540", PROCESSOR_PPC8540, MASK_STRICT_ALIGN | MASK_ISEL)
RS6000_CPU ("8548", PROCESSOR_PPC8548, MASK_STRICT_ALIGN | MASK_ISEL)
RS6000_CPU ("e500mc", PROCESSOR_PPCE500MC, MASK_PPC_GFXOPT | MASK_ISEL)
RS6000_CPU ("e500mc64", PROCESSOR_PPCE500MC64,
            MASK_POWERPC64 | MASK_PPC_GFXOPT | MASK_ISEL)
RS6000_CPU ("e5500", PROCESSOR_PPCE5500,
            MASK_POWERPC64 | MASK_PPC_GFXOPT | MASK_ISEL)
RS6000_CPU ("e6500", PROCESSOR_PPCE6500, POWERPC_7400_MASK | MASK_POWERPC64
            | MASK_MFCRF | MASK_ISEL)


So perhaps we should consider MASK_ISEL as power9 thing only for flags which
include power7-ish or later ISAs?
--- rs6000.c.jj4        2021-04-09 10:18:15.582266372 +0200
+++ rs6000.c    2021-04-19 16:30:07.033208577 +0200
@@ -5766,6 +5766,9 @@ rs6000_machine_from_flags (void)

   /* Disable the flags that should never influence the .machine selection.  */
   flags &= ~(OPTION_MASK_PPC_GFXOPT | OPTION_MASK_PPC_GPOPT);
+  if ((flags & (ISA_3_1_MASKS_SERVER
+               & ~(ISA_2_5_MASKS_SERVER | MASK_ISEL))) == 0)
+    flags &= ~MASK_ISEL;

   if ((flags & (ISA_3_1_MASKS_SERVER & ~ISA_3_0_MASKS_SERVER)) != 0)
     return "power10";

[Bug target/100108] [10/11 Regression] powerpc: recognize 32-bit CPU as POWER9 with -misel option

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100108

--- Comment #4 from Segher Boessenkool <segher at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #1)
> e500 support had been moved to the powerpcspe target; so assuming power9 for
> -misel is correct.
> 
> e500mc support is still there though.

There never *was* separate e500 support in GCC!

[Bug target/100108] [10/11 Regression] powerpc: recognize 32-bit CPU as POWER9 with -misel option

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100108

--- Comment #5 from Segher Boessenkool <segher at gcc dot gnu.org> ---
Created attachment 50629
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50629&action=edit
Proposed simpler patch

A simpler patch.  I'll commit this later today (if no one stops me).

[Bug target/100108] [10/11 Regression] powerpc: recognize 32-bit CPU as POWER9 with -misel option

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100108

Segher Boessenkool <segher at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|powerpc--netbsd             |powerpc
   Last reconfirmed|                            |2021-04-19
             Status|UNCONFIRMED                 |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |segher at gcc dot gnu.org
     Ever confirmed|0                           |1

[Bug target/100108] [10/11 Regression] powerpc: recognize 32-bit CPU as POWER9 with -misel option

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100108

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
LGTM.

[Bug target/100108] [10/11 Regression] powerpc: recognize 32-bit CPU as POWER9 with -misel option

[rin at NetBSD dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100108

--- Comment #7 from Rin Okuyama <rin at NetBSD dot org> ---
Thank you for discussion. The proposed patch works fine for me (except for
missing ``;'' at the end of the line).

[Bug target/100108] [10/11/12 Regression] powerpc: recognize 32-bit CPU as POWER9 with -misel option

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100108

--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Segher Boessenkool <segher@gcc.gnu.org>:

https://gcc.gnu.org/g:6156df483fa50a08f561b6c248819f2992aa380d

commit r12-9-g6156df483fa50a08f561b6c248819f2992aa380d
Author: Segher Boessenkool <segher@kernel.crashing.org>
Date:   Tue Apr 20 12:00:50 2021 +0000

    rs6000: Fix cpu selection w/ isel (PR100108)

    There are various non-IBM CPUs with isel as well, so it is easiest if we
    just don't consider that flag here (it is not needed).

    2021-04-20  Segher Boessenkool  <segher@kernel.crashing.org>

            PR target/100108
            * config/rs6000/rs6000.c (rs6000_machine_from_flags): Do not
consider
            OPTION_MASK_ISEL.

[Bug target/100108] [10/11/12 Regression] powerpc: recognize 32-bit CPU as POWER9 with -misel option

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100108

--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Segher Boessenkool
<segher@gcc.gnu.org>:

https://gcc.gnu.org/g:8bd3b0c11cb08f63d2ca41a21596d16635626661

commit r11-8264-g8bd3b0c11cb08f63d2ca41a21596d16635626661
Author: Segher Boessenkool <segher@kernel.crashing.org>
Date:   Tue Apr 20 12:00:50 2021 +0000

    rs6000: Fix cpu selection w/ isel (PR100108)

    There are various non-IBM CPUs with isel as well, so it is easiest if we
    just don't consider that flag here (it is not needed).

    2021-04-20  Segher Boessenkool  <segher@kernel.crashing.org>

            PR target/100108
            * config/rs6000/rs6000.c (rs6000_machine_from_flags): Do not
consider
            OPTION_MASK_ISEL.

    (cherry picked from commit 6156df483fa50a08f561b6c248819f2992aa380d)

[Bug target/100108] [10 Regression] powerpc: recognize 32-bit CPU as POWER9 with -misel option

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100108

--- Comment #10 from Segher Boessenkool <segher at gcc dot gnu.org> ---
Fixed on trunk and 11.  Will do 10 in a week or so.

[Bug target/100108] [10 Regression] powerpc: recognize 32-bit CPU as POWER9 with -misel option

[rin at NetBSD dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100108

--- Comment #11 from Rin Okuyama <rin at NetBSD dot org> ---
Segher, let me thank you again!

[Bug target/100108] [10 Regression] powerpc: recognize 32-bit CPU as POWER9 with -misel option

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100108

--- Comment #12 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Segher Boessenkool
<segher@gcc.gnu.org>:

https://gcc.gnu.org/g:5f665c1ca452673e9812cd92b07bd31441c0ac5b

commit r10-9814-g5f665c1ca452673e9812cd92b07bd31441c0ac5b
Author: Segher Boessenkool <segher@kernel.crashing.org>
Date:   Tue Apr 20 12:00:50 2021 +0000

    rs6000: Fix cpu selection w/ isel (PR100108)

    There are various non-IBM CPUs with isel as well, so it is easiest if we
    just don't consider that flag here (it is not needed).

    2021-04-20  Segher Boessenkool  <segher@kernel.crashing.org>

            PR target/100108
            * config/rs6000/rs6000.c (rs6000_machine_from_flags): Do not
consider
            OPTION_MASK_ISEL.

    (cherry picked from commit 6156df483fa50a08f561b6c248819f2992aa380d)

[Bug target/100108] [10 Regression] powerpc: recognize 32-bit CPU as POWER9 with -misel option

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100108

Segher Boessenkool <segher at gcc dot gnu.org> changed:

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

--- Comment #13 from Segher Boessenkool <segher at gcc dot gnu.org> ---
Fixed on GCC 10 and later.  Closing.