https://gcc.gnu.org/g:cf8a6940c9aaa5c213ca3d07b637825b2316d851
commit r12-11241-gcf8a6940c9aaa5c213ca3d07b637825b2316d851
Author: Jan Hubicka <j...@suse.cz>
Date: Fri Jun 24 13:52:44 2022 +0200
Fix stmt_kills_ref_p WRT external throws
Add missing check to stmt_kills_ref_p for case that function
is terminated by EH before call return value kills the ref. In the PR
I tried to construct testcase but I don't know how to do that until I
annotate EH code with fnspec attributes which I will do in separate patch
and add a testcase.
PR ipa/106057
* tree-ssa-alias.cc (stmt_kills_ref_p): Check for external throw.
(cherry picked from commit 7fd34782b95bbe1b4dc9936b8923f86d4aaee379)
Diff:
---
gcc/tree-ssa-alias.cc | 24 ++++++++++++++++++------
1 file changed, 18 insertions(+), 6 deletions(-)
diff --git a/gcc/tree-ssa-alias.cc b/gcc/tree-ssa-alias.cc
index 8fe4e9d9112a..e4fce6e52052 100644
--- a/gcc/tree-ssa-alias.cc
+++ b/gcc/tree-ssa-alias.cc
@@ -87,10 +87,11 @@ along with GCC; see the file COPYING3. If not see
This function tries to disambiguate two reference trees.
- bool ptr_deref_may_alias_global_p (tree)
+ bool ptr_deref_may_alias_global_p (tree, bool)
This function queries if dereferencing a pointer variable may
- alias global memory.
+ alias global memory. If bool argument is true, global memory
+ is considered to also include function local memory that escaped.
More low-level disambiguators are available and documented in
this file. Low-level disambiguators dealing with points-to
@@ -3346,11 +3347,18 @@ stmt_kills_ref_p (gimple *stmt, ao_ref *ref)
&& TREE_CODE (gimple_get_lhs (stmt)) != SSA_NAME
/* The assignment is not necessarily carried out if it can throw
and we can catch it in the current function where we could inspect
- the previous value.
+ the previous value. Similarly if the function can throw externally
+ and the ref does not die on the function return.
??? We only need to care about the RHS throwing. For aggregate
assignments or similar calls and non-call exceptions the LHS
- might throw as well. */
- && !stmt_can_throw_internal (cfun, stmt))
+ might throw as well.
+ ??? We also should care about possible longjmp, but since we
+ do not understand that longjmp is not using global memory we will
+ not consider a kill here since the function call will be considered
+ as possibly using REF. */
+ && !stmt_can_throw_internal (cfun, stmt)
+ && (!stmt_can_throw_external (cfun, stmt)
+ || !ref_may_alias_global_p (ref, false)))
{
tree lhs = gimple_get_lhs (stmt);
/* If LHS is literally a base of the access we are done. */
@@ -3447,8 +3455,12 @@ stmt_kills_ref_p (gimple *stmt, ao_ref *ref)
&& node->binds_to_current_def_p ()
&& (summary = get_modref_function_summary (node)) != NULL
&& summary->kills.length ()
+ /* Check that we can not trap while evaulating function
+ parameters. This check is overly conservative. */
&& (!cfun->can_throw_non_call_exceptions
- || !stmt_can_throw_internal (cfun, stmt)))
+ || (!stmt_can_throw_internal (cfun, stmt)
+ && (!stmt_can_throw_external (cfun, stmt)
+ || !ref_may_alias_global_p (ref, false)))))
{
for (auto kill : summary->kills)
{
