The following fixes PR105646, not diagnosing
int f1();
int f3(){
auto const & a = f1();
bool v3{v3};
return a;
}
with optimization because the early uninit diagnostic pass only
diagnoses always executed cases. The patch does this by
re-interpreting what always executed means and choosing to
ignore exceptional and abnormal control flow for this. At the
same time it improves things as suggested in a comment - when
the value-numbering run done without optimizing figures there's
a fallthru path, consider blocks on it as always executed.
Bootstrapped and tested on x86_64-unknown-linux-gnu.
OK?
Thanks,
Richard.
PR tree-optimization/105646
* tree-ssa-uninit.cc (warn_uninitialized_vars): Pre-compute
the set of fallthru reachable blocks from function entry
and use that to determine wlims.always_executed.
* g++.dg/uninit-pr105646.C: New testcase.
---
gcc/testsuite/g++.dg/uninit-pr105646.C | 17 +++++++++
gcc/tree-ssa-uninit.cc | 53 +++++++++++++++++++++-----
2 files changed, 61 insertions(+), 9 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/uninit-pr105646.C
diff --git a/gcc/testsuite/g++.dg/uninit-pr105646.C
b/gcc/testsuite/g++.dg/uninit-pr105646.C
new file mode 100644
index 00000000000..48ceb986ec6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/uninit-pr105646.C
@@ -0,0 +1,17 @@
+// { dg-do compile }
+// { dg-require-effective-target c++11 }
+// { dg-options "-O2 -Wuninitialized" }
+
+int f1();
+int f2(){
+ bool v2{v2}; // { dg-warning "is used uninitialized" }
+ auto const & a = f1();
+ return a;
+}
+int f3(){
+ auto const & a = f1();
+ // Diagnose the following when optimizing and as unconditional
+ // uninitialized use despite f1 possibly throwing
+ bool v3{v3}; // { dg-warning "is used uninitialized" }
+ return a;
+}
diff --git a/gcc/tree-ssa-uninit.cc b/gcc/tree-ssa-uninit.cc
index 7074c9117b2..b687e24a7e6 100644
--- a/gcc/tree-ssa-uninit.cc
+++ b/gcc/tree-ssa-uninit.cc
@@ -987,10 +987,49 @@ warn_uninitialized_vars (bool wmaybe_uninit)
wlimits wlims = { };
wlims.wmaybe_uninit = wmaybe_uninit;
- gimple_stmt_iterator gsi;
- basic_block bb;
+ auto_bb_flag ft_reachable (cfun);
+
+ /* Mark blocks that are always executed when we ignore provably
+ not executed and EH and abnormal edges. */
+ basic_block bb = single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun));
+ while (!(bb->flags & ft_reachable))
+ {
+ bb->flags |= ft_reachable;
+ edge e = find_fallthru_edge (bb->succs);
+ if (e && e->flags & EDGE_EXECUTABLE)
+ {
+ bb = e->dest;
+ continue;
+ }
+ /* Find a single executable edge. */
+ edge_iterator ei;
+ edge ee = NULL;
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ if (e->flags & EDGE_EXECUTABLE)
+ {
+ if (!ee)
+ ee = e;
+ else
+ {
+ ee = NULL;
+ break;
+ }
+ }
+ if (ee)
+ bb = ee->dest;
+ else
+ {
+ bb = get_immediate_dominator (CDI_POST_DOMINATORS, bb);
+ if (!bb || bb->index == EXIT_BLOCK)
+ break;
+ }
+ }
+
FOR_EACH_BB_FN (bb, cfun)
{
+ wlims.always_executed = (bb->flags & ft_reachable);
+ bb->flags &= ~ft_reachable;
+
edge_iterator ei;
edge e;
FOR_EACH_EDGE (e, ei, bb->preds)
@@ -1001,14 +1040,10 @@ warn_uninitialized_vars (bool wmaybe_uninit)
if (!e)
continue;
- basic_block succ = single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun));
- /* ??? This could be improved when we use a greedy walk and have
- some edges marked as not executable. */
- wlims.always_executed = dominated_by_p (CDI_POST_DOMINATORS, succ, bb);
-
if (wlims.always_executed)
warn_uninit_phi_uses (bb);
+ gimple_stmt_iterator gsi;
for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
{
gimple *stmt = gsi_stmt (gsi);
@@ -1029,7 +1064,7 @@ warn_uninitialized_vars (bool wmaybe_uninit)
FOR_EACH_SSA_USE_OPERAND (use_p, stmt, op_iter, SSA_OP_USE)
{
/* BIT_INSERT_EXPR first operand should not be considered
- a use for the purpose of uninit warnings. */
+ a use for the purpose of uninit warnings. */
if (gassign *ass = dyn_cast <gassign *> (stmt))
{
if (gimple_assign_rhs_code (ass) == BIT_INSERT_EXPR
@@ -1040,7 +1075,7 @@ warn_uninitialized_vars (bool wmaybe_uninit)
if (wlims.always_executed)
warn_uninit (OPT_Wuninitialized, use,
SSA_NAME_VAR (use), stmt);
- else if (wmaybe_uninit)
+ else if (wlims.wmaybe_uninit)
warn_uninit (OPT_Wmaybe_uninitialized, use,
SSA_NAME_VAR (use), stmt);
}
--
2.35.3
