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tree-optimization/112909 - uninit diagnostic with abnormal copy

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The following avoids spurious uninit diagnostics for SSA name
copies which mostly appear when the source is marked as abnormal
which prevents copy propagation.

To prevent regressions I remove the bail out for anonymous SSA
names in the PHI arg place from warn_uninitialized_phi leaving
that to warn_uninit where I handle SSA copies from a SSA name
which isn't anonymous.  In theory this might cause more
valid and false positive diagnostics to pop up.

	PR tree-optimization/112909
	* tree-ssa-uninit.cc (find_uninit_use): Look through a
	single level of SSA name copies with single use.

	* gcc.dg/uninit-pr112909.c: New testcase.
This commit is contained in:
Richard Biener 2023-12-08 09:14:43 +01:00
parent 3b93ce50af
commit 5e25baa7e5
2 changed files with 64 additions and 11 deletions
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28
gcc/testsuite/gcc.dg/uninit-pr112909.c Normal file
View file

@ -0,0 +1,28 @@
/* { dg-do compile } */
/* { dg-options "-O2 -Wuninitialized" } */
struct machine_thread_all_state {
int set;
} _hurd_setup_sighandler_state;
int _hurd_setup_sighandler_ss_0;
struct {
int ctx;
} *_hurd_setup_sighandler_stackframe;
void _setjmp();
void __thread_get_state();
int machine_get_basic_state(struct machine_thread_all_state *state) {
if (state->set)
__thread_get_state();
return 1;
}
int *_hurd_setup_sighandler() {
int *scp; /* { dg-bogus "used uninitialized" } */
if (_hurd_setup_sighandler_ss_0) {
_setjmp();
_hurd_setup_sighandler_state.set |= 5;
}
machine_get_basic_state(&_hurd_setup_sighandler_state);
scp = &_hurd_setup_sighandler_stackframe->ctx;
_setjmp();
return scp;
}

47
gcc/tree-ssa-uninit.cc
View file

@ -204,14 +204,29 @@ warn_uninit (opt_code opt, tree t, tree var, gimple *context,
{
var_def_stmt = SSA_NAME_DEF_STMT (t);
if (is_gimple_assign (var_def_stmt)
&& gimple_assign_rhs_code (var_def_stmt) == COMPLEX_EXPR)
if (gassign *ass = dyn_cast <gassign *> (var_def_stmt))
{
tree v = gimple_assign_rhs1 (var_def_stmt);
if (TREE_CODE (v) == SSA_NAME
&& has_undefined_value_p (v)
&& zerop (gimple_assign_rhs2 (var_def_stmt)))
var = SSA_NAME_VAR (v);
switch (gimple_assign_rhs_code (var_def_stmt))
{
case COMPLEX_EXPR:
{
tree v = gimple_assign_rhs1 (ass);
if (TREE_CODE (v) == SSA_NAME
&& has_undefined_value_p (v)
&& zerop (gimple_assign_rhs2 (ass)))
var = SSA_NAME_VAR (v);
break;
}
case SSA_NAME:
{
tree v = gimple_assign_rhs1 (ass);
if (TREE_CODE (v) == SSA_NAME
&& SSA_NAME_VAR (v))
var = SSA_NAME_VAR (v);
break;
}
default:;
}
}
if (gimple_call_internal_p (var_def_stmt, IFN_DEFERRED_INIT))
@ -1229,6 +1244,18 @@ find_uninit_use (gphi *phi, unsigned uninit_opnds, int *bb_to_rpo)
if (is_gimple_debug (use_stmt))
continue;
/* Look through a single level of SSA name copies. This is
important for copies involving abnormals which we can't always
proapgate out but which result in spurious unguarded uses. */
use_operand_p use2_p;
gimple *use2_stmt;
if (gimple_assign_ssa_name_copy_p (use_stmt)
&& single_imm_use (gimple_assign_lhs (use_stmt), &use2_p, &use2_stmt))
{
use_p = use2_p;
use_stmt = use2_stmt;
}
if (gphi *use_phi = dyn_cast<gphi *> (use_stmt))
{
unsigned idx = PHI_ARG_INDEX_FROM_USE (use_p);
@ -1262,9 +1289,9 @@ find_uninit_use (gphi *phi, unsigned uninit_opnds, int *bb_to_rpo)
e->src->index, e->dest->index);
print_gimple_stmt (dump_file, use_stmt, 0);
}
/* Found a phi use that is not guarded, mark the phi_result as
/* Found a phi use that is not guarded, mark the use as
possibly undefined. */
possibly_undefined_names->add (phi_result);
possibly_undefined_names->add (USE_FROM_PTR (use_p));
}
else
cands.safe_push (use_stmt);
@ -1318,8 +1345,6 @@ warn_uninitialized_phi (gphi *phi, unsigned uninit_opnds, int *bb_to_rpo)
unsigned phiarg_index = MASK_FIRST_SET_BIT (uninit_opnds);
tree uninit_op = gimple_phi_arg_def (phi, phiarg_index);
if (SSA_NAME_VAR (uninit_op) == NULL_TREE)
return;
location_t loc = UNKNOWN_LOCATION;
if (gimple_phi_arg_has_location (phi, phiarg_index))