| Message ID | YrRussd86hOeSK0M@kam.mff.cuni.cz |
|---|---|
| State | New |
| Headers | show |
| Series | Fix stmt_kills_ref_p wrt external throws | expand |
On Thu, 23 Jun 2022, Jan Hubicka wrote: > Hi, > this patch adds 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. > > Bootstrapped/regtested x86_64-linux, OK? > > PR ipa/106057 > * tree-ssa-alias.cc (stmt_kills_ref_p): Check for external throw. > diff --git a/gcc/tree-ssa-alias.cc b/gcc/tree-ssa-alias.cc > index b1e7a2d5afc..e427ee6744a 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 > @@ -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 diea on the function return. die. > ??? 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, stmt))))) you wanted , false here instead of , stmt? OK otherwise. Thanks, Richard. > { > for (auto kill : summary->kills) > { >
diff --git a/gcc/tree-ssa-alias.cc b/gcc/tree-ssa-alias.cc index b1e7a2d5afc..e427ee6744a 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 @@ -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 diea 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, stmt))))) { for (auto kill : summary->kills) {