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Fix stmt_kills_ref_p WRT external throws

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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.
This commit is contained in:
Jan Hubicka 2022-06-24 13:52:44 +02:00
parent 268b5c81e9
commit 7fd34782b9
1 changed files with 18 additions and 6 deletions
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24
gcc/tree-ssa-alias.cc
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@ -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
@ -3333,11 +3334,18 @@ 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. */
@ -3434,8 +3442,12 @@ 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)
{