[Bug optimization/14063] New: conditional around vec_dss() call disappears at -O2

["leblanc at skycomputers dot com" <gcc-bugzilla at gcc dot gnu dot org>]

The problem does NOT occur at lower optimization levels.

Configured with:
    ../gnu-tool-chain/gcc/configure
    --with-cpu=7450
    --enable-altivec
    --enable-shared
    --enable-threads=posix
    --enable-languages=c,c++
    --disable-checking
    --with-system-zlib
    --enable-__cxa_atexit
    --host=ppc-sky-linux
    --target=ppc-sky-linux
    --prefix=/usr/local

Thread model: posix

Source mike.c:
#include <altivec.h>
void dstt_bug(int i, int j, char *mem)
{
    if (i == 0)
        vec_dss(1);
}

Command line:
    gcc mike.c -S -O2 -maltivec

No messages; mike.s shows bug:
        .file   "mike.c"
        .section        ".text"
        .align 2
        .globl dstt_bug
        .type   dstt_bug, @function
dstt_bug:
        stwu 1,-16(1)
        dss 1
        addi 1,1,16
        blr
        .size   dstt_bug, .-dstt_bug
        .ident  "GCC: (GNU) 3.3"

mike.i:
# 1 "mike.c"
# 1 "<built-in>"
# 1 "<command line>"
# 1 "mike.c"
# 1 "/usr/local/lib/gcc-lib/ppc-sky-linux/3.3/include/altivec.h" 1 3 4
# 52 "/usr/local/lib/gcc-lib/ppc-sky-linux/3.3/include/altivec.h" 3 4
extern int __altivec_link_error_invalid_argument ();
# 2 "mike.c" 2
void dstt_bug(int i, int j, char *mem)
{
    if (i == 0)
        __builtin_altivec_dss ((1));
}

-- 
           Summary: conditional around vec_dss() call disappears at -O2
           Product: gcc
           Version: 3.3
            Status: UNCONFIRMED
          Severity: critical
          Priority: P2
         Component: optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: leblanc at skycomputers dot com
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: ppc-sky-linux
GCC target triplet: ppc-sky-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14063