https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123043
Bug ID: 123043
Summary: [16 Regression] ICE on zlib -O3: GIMPLE pass: vect:
verify_ssa failed: definition in block 133 does not
dominate use in block 130
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: slyfox at gcc dot gnu.org
Target Milestone: ---
zlib gets a wrong code on i686-linux for me when built on gcc-master since
r16-5780-g65a3849eb46df2 . I was not able to extract the full example from zlib
(too much code).
When building `zlib` with `--enable-checking=all` gcc ICEs and points at the
same function it stopped at.
Minimal ICE reproducer:
// $ cat inffast.c.c
char sad_memcpy_pout;
int inflate_fast_len;
void inflate_fast() {
char *out = &sad_memcpy_pout, *from;
do {
*out++ = *from++;
*out++ = *from++;
inflate_fast_len -= 3;
} while (inflate_fast_len > 2);
}
Crashing:
gcc/xgcc -Bgcc -c inffast.c.c -o bug.o -O3
inffast.c.c: In function ‘inflate_fast’:
inffast.c.c:3:6: error: definition in block 17 does not dominate use in block
14
3 | void inflate_fast() {
| ^~~~~~~~~~~~
for SSA_NAME: tmp.16_68 in statement:
_19 = PHI <tmp.16_68(14), _38(6), _57(15)>
PHI argument
tmp.16_68
for PHI node
_19 = PHI <tmp.16_68(14), _38(6), _57(15)>
during GIMPLE pass: vect
inffast.c.c:3:6: internal compiler error: verify_ssa failed
0xa3322e4 diagnostics::context::diagnostic_impl(rich_location*,
diagnostics::metadata const*, diagnostics::option_id, char const*, char**,
diagnostics::kind)
???:0
0xa32531f internal_error(char const*, ...)
???:0
0x8f90305 verify_ssa(bool, bool)
???:0
0x8b26147 execute_function_todo(function*, void*)
???:0
0x8b26206 do_per_function(void (*)(function*, void*), void*)
???:0
0x8b2635b execute_todo(unsigned int)
???:0
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
$ gcc/xgcc -Bgcc -v
Reading specs from gcc/specs
COLLECT_GCC=gcc/xgcc
COLLECT_LTO_WRAPPER=gcc/lto-wrapper
Target: i686-unknown-linux-gnu
Configured with: /home/slyfox/dev/git/gcc/configure --disable-multilib
--disable-bootstrap --disable-lto --disable-libsanitizer --enable-languages=c
CFLAGS='-O1 -g0' CXXFLAGS='-O1 -g0' LDFLAGS='-O1 -g0'
--build=i686-unknown-linux-gnu --host=i686-unknown-linux-gnu
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 16.0.0 20251207 (experimental) (GCC)
