[Bug tree-optimization/50039] New: Segfault in vect_operation_fits_smaller_type()

["arthur.j.odwyer at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50039

             Bug #: 50039
           Summary: Segfault in vect_operation_fits_smaller_type()
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: arthur.j.odwyer@gmail.com


Created attachment 24972
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24972
Output of "ajo-gcc -std=c99 -O2 -ftree-vectorize -fno-tree-fre test.c -v"

This failure reproduces for me with svn revision 177610 (2011-08-09), going
back at least as far as 177466 (2011-08-05). I'm on Ubuntu 10.10, x86-64.

Incidentally, it might be a good idea to put some "redundant" null-checks in
the tree vectorizer. I see a ton of segfaults being reported against it as far
back as 4.2. If those were ICEs instead, it might be easier to distinguish
duplicates; and IMHO ICEs are preferable to segfaults anyway.

cat >test.c <<EOF
extern unsigned char g_5;
extern int g_31, g_76;
int main(void) {
    for (int j=0; j < 2; ++j) {
        g_31 = -3;
        for (int i=0; i < 2; ++i)
          g_76 = (g_31 ? g_31+1 : 0) ^ g_5;
    }
}
EOF
gcc -std=c99 -O2 -ftree-vectorize -fno-tree-fre test.c

test.c: In function âmainâ:
test.c:3:5: internal compiler error: Segmentation fault


(gdb) run
Program received signal SIGSEGV, Segmentation fault.
vect_operation_fits_smaller_type (stmts=0x7fffffffde88, 
    type_in=0x7fffffffde78, type_out=0x7fffffffde80)
    at ../../gcc/tree-vect-patterns.c:982
982              if (STMT_VINFO_RELATED_STMT (vinfo_for_stmt (def_stmt)))
(gdb) backtrace
#0  vect_operation_fits_smaller_type (stmts=0x7fffffffde88,
type_in=0x7fffffffde78, type_out=0x7fffffffde80)
    at ../../gcc/tree-vect-patterns.c:982
#1  vect_recog_over_widening_pattern (stmts=0x7fffffffde88,
type_in=0x7fffffffde78, type_out=0x7fffffffde80)
    at ../../gcc/tree-vect-patterns.c:1088
#2  0x0000000000d462e9 in vect_pattern_recog_1 (loop_vinfo=Unhandled dwarf
expression opcode 0xf3)
    at ../../gcc/tree-vect-patterns.c:1284
[...]


This test case is reduced from the output of Csmith 2.1.0 (git hash 210eda7,
https://github.com/Quuxplusone/csmith/), using the following command line:
csmith --paranoid --longlong --no-pointers --arrays --no-jumps --consts
--no-volatiles --no-checksum --no-divs --no-muls --no-bitfields
--no-packed-struct -s 1902267639