[Bug tree-optimization/97953] ICE (segfault) during GIMPLE pass: loopdone compiling libgcc/config/libbid/bid128_fma.c:190:1

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97953

--- Comment #15 from Martin Liška <marxin at gcc dot gnu.org> ---
Created attachment 49624
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49624&action=edit
debugging patch

All right it will be for Richi. I suspect it's a do_hoist_insertion.

reduced test-case:

$ cat /tmp/bid.i
int __bid_ten2k64_res_0, __bid_ten2k64_ind;
void __bid_round64_2_18();

void __bid_ten2k64() {
  for (; __bid_ten2k64_ind <= 9; __bid_ten2k64_ind++)
    if (__bid_ten2k64_res_0)
      break;
  if (__bid_ten2k64_ind)
    __bid_round64_2_18();
}

Steps to reproduce:
1) git co bd87cc14ebdb6789e067fb1828d5808407c308b3
2) patch -p1 < debug.patch
3) mkdir objdir
4) cd objdir
5) ../configure --disable-checking --disable-werror
--enable-languages=c,c++,fortran --disable-multilib
6) make -j16 (you can also use make -j16 'STAGE1_CFLAGS=-g -O2')

... then it build stage2 compiler and crashes in somewhere in libgcc (using the
compiler)

$ ./gcc/xgcc -Bgcc /tmp/bid.i -O2 -c -fverbose-asm
__bid_ten2k64_ind.2_11 = PHI <_3(13), __bid_ten2k64_ind.2_12(4)>
use->stmt: 0x7ffff7548400, use->stmt->code: 18
_3 = __bid_ten2k64_ind.2_11 + 1;
cand->incremented_at: 0x7ffff7544000, cand->incremented_at->code: 6
during GIMPLE pass: ivopts
/tmp/bid.i: In function ‘__bid_ten2k64’:
/tmp/bid.i:4:6: internal compiler error: XXXXXX, code==18

    4 | void __bid_ten2k64() {
      |      ^~~~~~~~~~~~~
0x7ffff7695151 __libc_start_main
        ../csu/libc-start.c:314
0x5ffafd ???
        ../sysdeps/x86_64/start.S:120
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

as seen rewrite_use_nonlinear_expr is miscompiled where code == 18 is
GIMPLE_PHI which is handled in the switch

You can do:

$ cd gcc
$ /home/marxin/Programming/gcc2/objdir/./prev-gcc/xg++
-B/home/marxin/Programming/gcc2/objdir/./prev-gcc/
-B/usr/local/x86_64-pc-linux-gnu/bin/ -nostdinc++
-B/home/marxin/Programming/gcc2/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/src/.libs
-B/home/marxin/Programming/gcc2/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/libsupc++/.libs

-I/home/marxin/Programming/gcc2/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/include/x86_64-pc-linux-gnu

-I/home/marxin/Programming/gcc2/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/include
 -I/home/marxin/Programming/gcc2/libstdc++-v3/libsupc++
-L/home/marxin/Programming/gcc2/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/src/.libs
-L/home/marxin/Programming/gcc2/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/libsupc++/.libs
 -fno-PIE -c   -g -O2 -fno-checking -gtoggle  -DIN_GCC     -fno-exceptions
-fno-rtti -fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings
-Wcast-qual -Wno-error=format-diag -Wmissing-format-attribute
-Woverloaded-virtual -pedantic -Wno-long-long -Wno-variadic-macros
-Wno-overlength-strings   -DHAVE_CONFIG_H -I. -I. -I../../gcc -I../../gcc/.
-I../../gcc/../include -I../../gcc/../libcpp/include 
-I../../gcc/../libdecnumber -I../../gcc/../libdecnumber/bid -I../libdecnumber
-I../../gcc/../libbacktrace   -o tree-ssa-loop-ivopts.o -MT
tree-ssa-loop-ivopts.o -MMD -MP -MF ./.deps/tree-ssa-loop-ivopts.TPo
../../gcc/tree-ssa-loop-ivopts.c -fdbg-cnt=hoisting:932-933 && m && ./xgcc -B.
-O2 -c /tmp/bid.i -fverbose-asm

as seen is first bad debug counter value: -fdbg-cnt=hoisting:932-933, good one
is:
-fdbg-cnt=hoisting:932-932

or you can find your value with

dbgcnt-bisect.py '/home/marxin/Programming/gcc2/objdir/./prev-gcc/xg++
-B/home/marxin/Programming/gcc2/objdir/./prev-gcc/
-B/usr/local/x86_64-pc-linux-gnu/bin/ -nostdinc++
-B/home/marxin/Programming/gcc2/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/src/.libs
-B/home/marxin/Programming/gcc2/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/libsupc++/.libs

-I/home/marxin/Programming/gcc2/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/include/x86_64-pc-linux-gnu

-I/home/marxin/Programming/gcc2/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/include
 -I/home/marxin/Programming/gcc2/libstdc++-v3/libsupc++
-L/home/marxin/Programming/gcc2/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/src/.libs
-L/home/marxin/Programming/gcc2/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/libsupc++/.libs
 -fno-PIE -c   -g -O2 -fno-checking -gtoggle  -DIN_GCC     -fno-exceptions
-fno-rtti -fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings
-Wcast-qual -Wno-error=format-diag -Wmissing-format-attribute
-Woverloaded-virtual -pedantic -Wno-long-long -Wno-variadic-macros
-Wno-overlength-strings   -DHAVE_CONFIG_H -I. -I. -I../../gcc -I../../gcc/.
-I../../gcc/../include -I../../gcc/../libcpp/include 
-I../../gcc/../libdecnumber -I../../gcc/../libdecnumber/bid -I../libdecnumber
-I../../gcc/../libbacktrace   -o tree-ssa-loop-ivopts.o -MT
tree-ssa-loop-ivopts.o -MMD -MP -MF ./.deps/tree-ssa-loop-ivopts.TPo
../../gcc/tree-ssa-loop-ivopts.c' 'make -j16 && ./xgcc -B. -O2 -c /tmp/bid.i'
hoisting 2000

The script is from:
https://github.com/marxin/script-misc