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c-family: avoid compile-time-hog in c_genericize [PR108880]

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This fixes a compile-time hog with UBSan.  This only happened in cc1 but
not cc1plus.  The problem is ultimately that c_genericize_control_stmt/
STATEMENT_LIST -> walk_tree_1 doesn't use a hash_set to remember visited
nodes, so it kept on recursing for a long time.  We should be able to
use the pset that c_genericize created.  We just need to use walk_tree
instead of walk_tree_w_d so that the pset is explicit.

	PR c/108880

gcc/c-family/ChangeLog:

	* c-gimplify.cc (c_genericize_control_stmt) <case STATEMENT_LIST>: Pass
	pset to walk_tree_1.
	(c_genericize): Call walk_tree with an explicit pset.

gcc/testsuite/ChangeLog:

	* c-c++-common/ubsan/pr108880.c: New test.
This commit is contained in:
Marek Polacek 2023-02-22 15:17:03 -05:00
parent 31303c9b5b
commit 1370014f2e
2 changed files with 20 additions and 3 deletions
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10
gcc/c-family/c-gimplify.cc
View file

@ -511,12 +511,15 @@ c_genericize_control_stmt (tree *stmt_p, int *walk_subtrees, void *data,
STATEMENT_LIST wouldn't be present at all the resulting
expression wouldn't have TREE_SIDE_EFFECTS set, so make sure
to clear it even on the STATEMENT_LIST in such cases. */
hash_set<tree> *pset = (c_dialect_cxx ()
? nullptr
: static_cast<hash_set<tree> *>(data));
for (i = tsi_start (stmt); !tsi_end_p (i); tsi_next (&i))
{
tree t = tsi_stmt (i);
if (TREE_CODE (t) != DEBUG_BEGIN_STMT && nondebug_stmts < 2)
nondebug_stmts++;
walk_tree_1 (tsi_stmt_ptr (i), func, data, NULL, lh);
walk_tree_1 (tsi_stmt_ptr (i), func, data, pset, lh);
if (TREE_CODE (t) != DEBUG_BEGIN_STMT
&& (nondebug_stmts > 1 || TREE_SIDE_EFFECTS (tsi_stmt (i))))
clear_side_effects = false;
@ -572,8 +575,9 @@ c_genericize (tree fndecl)
bc_state_t save_state;
push_cfun (DECL_STRUCT_FUNCTION (fndecl));
save_bc_state (&save_state);
walk_tree_without_duplicates (&DECL_SAVED_TREE (fndecl),
c_genericize_control_r, NULL);
hash_set<tree> pset;
walk_tree (&DECL_SAVED_TREE (fndecl), c_genericize_control_r, &pset,
&pset);
restore_bc_state (&save_state);
pop_cfun ();
}

13
gcc/testsuite/c-c++-common/ubsan/pr108880.c Normal file
View file

@ -0,0 +1,13 @@
/* PR c/108880 */
/* { dg-do compile } */
/* { dg-options "-fsanitize=undefined" } */
long a;
short b, e;
char c;
int d, f, g;
void h() {
int i;
f &= i ^= (((g &= 0 / d / d % 8 << 0 << 2) % a >> e) / c >> b) / 1 % 8 << 3;
}
int main() {}