[Bug target/65810] New: powerpc64 libgfortran alignment issue?

[Bug target/65810] New: powerpc64 libgfortran alignment issue?

[amodra at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65810

            Bug ID: 65810
           Summary: powerpc64 libgfortran alignment issue?
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: amodra at gmail dot com

Testsuite results between two identical powerpc64-linux builds, except for the
source path name, differ.

+FAIL: gfortran.dg/fmt_en.f90   -O0  execution test
+FAIL: gfortran.dg/fmt_en.f90   -O0   scan-file All kinds rounded to nearest
+FAIL: gfortran.dg/fmt_en.f90   -O1  execution test
+FAIL: gfortran.dg/fmt_en.f90   -O1   scan-file All kinds rounded to nearest
+FAIL: gfortran.dg/fmt_en.f90   -O2  execution test
+FAIL: gfortran.dg/fmt_en.f90   -O2   scan-file All kinds rounded to nearest
+FAIL: gfortran.dg/fmt_en.f90   -O3 -fomit-frame-pointer  execution test
+FAIL: gfortran.dg/fmt_en.f90   -O3 -fomit-frame-pointer -funroll-all-loops
-finline-functions  execution test
+FAIL: gfortran.dg/fmt_en.f90   -O3 -fomit-frame-pointer -funroll-all-loops
-finline-functions   scan-file All kinds rounded to nearest
+FAIL: gfortran.dg/fmt_en.f90   -O3 -fomit-frame-pointer -funroll-loops 
execution test
+FAIL: gfortran.dg/fmt_en.f90   -O3 -fomit-frame-pointer -funroll-loops  
scan-file All kinds rounded to nearest
+FAIL: gfortran.dg/fmt_en.f90   -O3 -fomit-frame-pointer   scan-file All kinds
rounded to nearest
+FAIL: gfortran.dg/fmt_en.f90   -O3 -g  execution test
+FAIL: gfortran.dg/fmt_en.f90   -O3 -g   scan-file All kinds rounded to nearest
+FAIL: gfortran.dg/fmt_en.f90   -Os  execution test
+FAIL: gfortran.dg/fmt_en.f90   -Os   scan-file All kinds rounded to nearest
+FAIL: gfortran.dg/large_real_kind_1.f90   -O0  execution test
+FAIL: gfortran.dg/large_real_kind_1.f90   -O1  execution test
+FAIL: gfortran.dg/large_real_kind_1.f90   -O2  execution test
+FAIL: gfortran.dg/large_real_kind_1.f90   -O3 -fomit-frame-pointer  execution
test
+FAIL: gfortran.dg/large_real_kind_1.f90   -O3 -fomit-frame-pointer
-funroll-all-loops -finline-functions  execution test
+FAIL: gfortran.dg/large_real_kind_1.f90   -O3 -fomit-frame-pointer
-funroll-loops  execution test
+FAIL: gfortran.dg/large_real_kind_1.f90   -O3 -g  execution test
+FAIL: gfortran.dg/large_real_kind_1.f90   -Os  execution test
+FAIL: gfortran.dg/quad_2.f90   -O0  execution test
+FAIL: gfortran.dg/quad_2.f90   -O1  execution test
+FAIL: gfortran.dg/quad_2.f90   -O2  execution test
+FAIL: gfortran.dg/quad_2.f90   -O3 -fomit-frame-pointer  execution test
+FAIL: gfortran.dg/quad_2.f90   -O3 -fomit-frame-pointer -funroll-all-loops
-finline-functions  execution test
+FAIL: gfortran.dg/quad_2.f90   -O3 -fomit-frame-pointer -funroll-loops 
execution test
+FAIL: gfortran.dg/quad_2.f90   -O3 -g  execution test
+FAIL: gfortran.dg/quad_2.f90   -Os  execution test

Both compilers configured with
CC="gcc -m64" CXX="g++ -m64" \
${gcc_src}/configure --build=powerpc64-linux \
--with-cpu=power7 \
--disable-nls --enable-__cxa_atexit --enable-secureplt \
--with-long-double-128 --enable-gnu-indirect-function \
--enable-languages=all,go --enable-lto

In one case gcc_src=/home/amodra/src/gcc-5-virgin
the other gcc_src=/home/amodra/src/gcc-5-vir

Running the testcases by hand with different LD_LIBRARY_PATH show the problem
is in libgfortran, not the testcase code.  valgrind doesn't show any
uninitialized accesses.  

Looking at quad_2.f90 under gdb, I see the abort is due to str3 having an extra
leading space.

[Bug target/65810] powerpc64 libgfortran alignment issue?

[jvdelisle at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65810

Jerry DeLisle <jvdelisle at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jvdelisle at gcc dot gnu.org

--- Comment #1 from Jerry DeLisle <jvdelisle at gcc dot gnu.org> ---
Could you post the output of: gfortran -v so we can confirm the version number.

I am not seeing it show up on any of the automatic testers.  I tried to access
the Power7 machine I usually use and can't get in (comm problems).

[Bug target/65810] powerpc64 libgfortran alignment issue?

[bergner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65810

--- Comment #2 from Peter Bergner <bergner at gcc dot gnu.org> ---
(In reply to Jerry DeLisle from comment #1)
> I am not seeing it show up on any of the automatic testers.  I tried to
> access the Power7 machine I usually use and can't get in (comm problems).

There is the gcc110 GCC compiler farm power7 system.

[Bug target/65810] powerpc64 libgfortran alignment issue?

[amodra at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65810

--- Comment #3 from Alan Modra <amodra at gmail dot com> ---
amodra@bns:~/build/gcc-5-virgin> gcc/gfortran -v
Using built-in specs.
COLLECT_GCC=gcc/gfortran
Target: powerpc64-linux
Configured with: /home/amodra/src/gcc-5-virgin/configure
--build=powerpc64-linux --with-cpu=power7 --disable-nls --enable-__cxa_atexit
--enable-secureplt --with-long-double-128 --enable-gnu-indirect-function
--enable-languages=all,go --enable-lto
Thread model: posix
gcc version 5.0.1 20150416 (prerelease) (GCC)

[Bug target/65810] powerpc64 libgfortran alignment issue?

[amodra at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65810

Alan Modra <amodra at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2015-04-20
           Assignee|unassigned at gcc dot gnu.org      |amodra at gmail dot com
     Ever confirmed|0                           |1

--- Comment #4 from Alan Modra <amodra at gmail dot com> ---
Here's the bad code
   0x00000fffb7f6c438 <write_float+3736>:    addis   r9,r2,-2
   0x00000fffb7f6c43c <write_float+3740>:    li      r27,0
   0x00000fffb7f6c440 <write_float+3744>:    lfd     f24,32760(r9)
   0x00000fffb7f6c444 <write_float+3748>:    lfd     f25,-32768(r9)

It's from write_float.def:888
  r *= 10;
so is supposed to be loading up 10.0L but instead gets a completely bogus low
double as seen in "d" below.
__gcc_qmul (a=1, b=0, c=10, d=-7.3968712249802237e+209)

So not something odd in libgfortran..

Hmm
p/x $r2
$31 = 0xfffb7fa1bd8

So, gcc emits toc sections with alignment of 8 bytes, which the linker
respects, leading to a toc pointer (r2) that can only be assumed to be 8 byte
aligned.  This completely breaks rs6000.c:offsettable_ok_by_alignment.
My bug.  Short term fix will be to limit offsettable_ok_by_alignment to 8 byte
alignment.  Longer term, modify the linker to increase r2 alignment.

[Bug target/65810] powerpc64 alignment of r2 insufficient for loading long-double constants

[dominiq at lps dot ens.fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65810

--- Comment #5 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
Why is this not seen on powerpc64-unknown-linux-gnu at
https://gcc.gnu.org/ml/gcc-testresults/2015-04/msg02317.html?

[Bug target/65810] powerpc64 alignment of r2 insufficient for loading long-double constants

[amodra at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65810

--- Comment #6 from Alan Modra <amodra at gmail dot com> ---
It isn't seen most of the time because the failure happens only when r2 isn't
16-byte aligned (50% chance) and the r2 offset to a long double constant is
n*64k+32k-8 (0.012% chance per long double).  libgfortran stores paths for
error messages in .rodata, so source path can affect placement of those long
double constants.  I'm just lucky.

[Bug target/65810] powerpc64 alignment of r2 insufficient for loading long-double constants

[amodra at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65810

--- Comment #7 from Alan Modra <amodra at gcc dot gnu.org> ---
Author: amodra
Date: Tue Apr 28 03:47:19 2015
New Revision: 222498

URL: https://gcc.gnu.org/viewcvs?rev=222498&root=gcc&view=rev
Log:
        PR target/65810
        * config/rs6000/rs6000.c (POWERPC64_TOC_POINTER_ALIGNMENT): Define.
        (offsettable_ok_by_alignment): Use minimum of decl and toc
        pointer alignment.  Replace dead code with assertion.
        (use_toc_relative_ref): Add mode arg.  Return false in -mcmodel=medium
        case if size exceeds toc pointer alignment.
        (rs6000_legitimize_reload_address): Update use_toc_relative_ref call.
        (rs6000_emit_move): Likewise.
        * configure.ac: Add linker toc pointer alignment check.
        * configure: Regenerate.
        * config.in: Regenerate.


Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config.in
    trunk/gcc/config/rs6000/rs6000.c
    trunk/gcc/configure
    trunk/gcc/configure.ac

[Bug target/65810] powerpc64 alignment of r2 insufficient for loading long-double constants

[amodra at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65810

Alan Modra <amodra at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |6.0

--- Comment #8 from Alan Modra <amodra at gmail dot com> ---
Fixed