https://gcc.gnu.org/bugzilla/show_bug.cgi?id=128209
Bug ID: 128209
Summary: [17 Regression] valgrind error in
vn_is_backedge(edge_def*, void*)
(tree-ssa-sccvn.cc:4103)
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: dcb314 at hotmail dot com
Target Milestone: ---
Created attachment 65981
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=65981&action=edit
C++ source code
The attached C++ code does this with recent valgrinded trunk g++:
$ ~/gcc/results.20261026.valgrind/bin/g++ -c -O3 bug1257.cc
==820072== Conditional jump or move depends on uninitialised value(s)
==820072== at 0x125654F: vn_is_backedge(edge_def*, void*)
(tree-ssa-sccvn.cc:4103)
==820072== by 0x113FF82: get_continuation_for_phi(gphi*, ao_ref*, bool,
unsigned int&, bitmap_head**, void* (*)(ao_ref*, tree_node*, void*,
translate_flags*), void*, bool (*)(edge_def*, void*), translate_flags)
(tree-ssa-alias.cc:3913)
==820072== by 0x1140252: walk_non_aliased_vuses(ao_ref*, tree_node*, bool,
void* (*)(ao_ref*, tree_node*, void*), void* (*)(ao_ref*, tree_node*, void*,
translate_flags*), bool (*)(edge_def*, void*), tree_node* (*)(tree_node*),
unsigned int&, void*) (tree-ssa-alias.cc:4010)
==820072== by 0x1256F78: vn_reference_lookup(tree_node*, tree_node*,
vn_lookup_kind, vn_reference_s**, bool, tree_node**, tree_node*, bool)
(tree-ssa-sccvn.cc:4332)
It seems to work for g:708cc223b0f8b96c, but seems broken for
g:011070daf505fd1d
I will have a go at a reduction. Compiler is
$ /home/dcb42/gcc/results.20261026.valgrind/bin/g++ -v
Using built-in specs.
COLLECT_GCC=/home/dcb42/gcc/results.20261026.valgrind/bin/g++
COLLECT_LTO_WRAPPER=/home/dcb42/gcc/results.20261026.valgrind/libexec/gcc/x86_64-pc-linux-gnu/17.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../trunk/configure
--prefix=/home/dcb42/gcc/results.20261026.valgrind --disable-bootstrap
--disable-doc --disable-fixincludes --disable-multilib
--with-pkgversion=011070daf505fd1d --enable-checking=valgrind
--enable-languages=c,c++,fortran
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 17.0.0 20261020 (experimental) (011070daf505fd1d)
$
