[Bug fortran/45636] New: Failed to fold simple Fortran string

[Bug fortran/45636] New: Failed to fold simple Fortran string

[hjl dot tools at gmail dot com]

For this simple Fortran string:

[hjl@gnu-6 pr45634]$ cat pr45634.f90 
      SUBROUTINE RCRDRD (VTYP)
      CHARACTER(4), INTENT(OUT) :: VTYP 
      CHARACTER(1), SAVE :: DBL = "D" 
      VTYP = DBL
      END

GCC generates:

[hjl@gnu-6 pr45634]$ cat pr45634.s 
        .file   "pr45634.f90"
        .text
        .p2align 4,,15
        .globl  rcrdrd_
        .type   rcrdrd_, @function
rcrdrd_:
.LFB0:
        .cfi_startproc
        movzbl  dbl.1557(%rip), %eax
        movw    $8224, 1(%rdi)
        movb    $32, 3(%rdi)
        movb    %al, (%rdi)
        ret
        .cfi_endproc
.LFE0:
        .size   rcrdrd_, .-rcrdrd_
        .section        .rodata
        .type   dbl.1557, @object
        .size   dbl.1557, 1
dbl.1557:
        .ascii  "D"
        .ident  "GCC: (GNU) 4.6.0 20100910 (experimental)"
        .section        .note.GNU-stack,"",@progbits

IFORT generates:

[hjl@gnu-6 pr45634]$ cat icc.s
# -- Machine type EFI2
# mark_description "Intel(R) Fortran Compiler XE for applications running on
Intel(R) 64, Version 12.0.0 Beta Build 20100512";
# mark_description "-O3 -S";
        .file "pr45634.f90"
        .text
..TXTST0:
# -- Begin  rcrdrd_
# mark_begin;
       .align    16,0x90
        .globl rcrdrd_
rcrdrd_:
# parameter 1: %rdi
# parameter 2: %rsi
..B1.1:                         # Preds ..B1.0
..___tag_value_rcrdrd_.1:                                       #1.18
        movl      $538976324, (%rdi)                            #4.7
        ret                                                     #5.7


-- 
           Summary: Failed to fold simple Fortran string
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: hjl dot tools at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45636

[Bug fortran/45636] Failed to fold simple Fortran string

[kargl at gcc dot gnu dot org]

------- Comment #1 from kargl at gcc dot gnu dot org  2010-09-10 15:12 -------
I have a slightly different result with your code.

troutmask:sgk[212] gfc4x -c -O g.f90
g.f90: In function 'rcrdrd':
g.f90:1:0: internal compiler error: in build_int_cst_wide, at tree.c:1218
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.

If I replace the SAVE attribute by PARAMETER (which will most
likely cause the folding you want), everything compiles fine.
The ICE also goes away if I increase the length of DBL from
one to any larger value.

troutmask:sgk[219] gfc4x -v
Using built-in specs.
COLLECT_GCC=/home/sgk/work/4x/bin/gfortran
COLLECT_LTO_WRAPPER=/usr/home/sgk/work/4x/bin/../libexec/gcc/x86_64-unknown-freebsd9.0/4.6.0/lto-wrapper
Target: x86_64-unknown-freebsd9.0
Configured with: ../gcc4x/configure --prefix=/home/sgk/work/4x
--enable-languages=c,fortran --disable-libmudflap --disable-bootstrap
--with-quad=/home/sgk/work
Thread model: posix
gcc version 4.6.0 20100909 (experimental) (GCC) 


-- 

kargl at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ice-on-valid-code


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45636

[Bug fortran/45636] Failed to fold simple Fortran string

[kargl at gcc dot gnu dot org]

------- Comment #2 from kargl at gcc dot gnu dot org  2010-09-10 15:20 -------
The -fdump-tree-original for HJ's original code look like

rcrdrd (character(kind=1)[1:4] & restrict vtyp, integer(kind=4) _vtyp)
{
  static character(kind=1) dbl[1:1] = "D";

  (MEM[(c_char * {ref-all})vtyp] = MEM[(c_char * {ref-all})&dbl];, (void *)
vtyp;);
  __builtin_memset ((void *) vtyp + 1, 32, 3);
}

If I increase the length of DBL to 2, then the dump looks like

rcrdrd (character(kind=1)[1:4] & restrict vtyp, integer(kind=4) _vtyp)
{
  static character(kind=1) dbl[1:2] = "D ";

  __builtin_memmove ((void *) vtyp, (void *) &dbl, 2);
  __builtin_memset ((void *) vtyp + 2, 32, 2);
}


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45636

[Bug fortran/45636] Failed to fold simple Fortran string

[hjl dot tools at gmail dot com]

------- Comment #3 from hjl dot tools at gmail dot com  2010-09-10 15:32 -------
(In reply to comment #1)
> I have a slightly different result with your code.
> 
> troutmask:sgk[212] gfc4x -c -O g.f90
> g.f90: In function 'rcrdrd':
> g.f90:1:0: internal compiler error: in build_int_cst_wide, at tree.c:1218
> Please submit a full bug report,
> with preprocessed source if appropriate.
> See <http://gcc.gnu.org/bugs.html> for instructions.
> 
>

It is fixed by

http://gcc.gnu.org/ml/gcc-cvs/2010-09/msg00475.html


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45636

[Bug fortran/45636] Failed to fold simple Fortran string

[kargl at gcc dot gnu dot org]

------- Comment #4 from kargl at gcc dot gnu dot org  2010-09-10 15:34 -------
(In reply to comment #3)
> (In reply to comment #1)
> > I have a slightly different result with your code.
> > 
> > troutmask:sgk[212] gfc4x -c -O g.f90
> > g.f90: In function 'rcrdrd':
> > g.f90:1:0: internal compiler error: in build_int_cst_wide, at tree.c:1218
> > Please submit a full bug report,
> > with preprocessed source if appropriate.
> > See <http://gcc.gnu.org/bugs.html> for instructions.
> > 
> >
> 
> It is fixed by
> 
> http://gcc.gnu.org/ml/gcc-cvs/2010-09/msg00475.html
> 

HJ,

Thanks.  I updated by trunk right before your patch,
so I missed it my most recent build.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45636

[Bug fortran/45636] Failed to fold simple Fortran string

[jakub at gcc dot gnu dot org]

------- Comment #5 from jakub at gcc dot gnu dot org  2010-09-10 15:47 -------
For arbitrary lengths (both of the constant string and of the padding) the
memmove (which will be optimized to memcpy as the source is read-only) + memset
is the best thing to do, replacing say
memmove (x, "900 bytes long string", 900);
memset (x + 900, ' ', 100);
would be very .rodata size unfriendly.
So, the question is, do we want to optimize this for very small sizes of both
(what sizes?  Should we call can_store_by_pieces to determine that from the
FE?)
in the FE by transforming that say
memmove (x, "ABCDE", 5);
memset (x + 5, ' ', 3);
into
memcpy (x, "ABCDE   ", 8);
or should we do this generically in the middle-end, where we'd do this
transformation for such cases even for other languages?


-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ice-on-valid-code


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45636