[gcc(refs/users/aoliva/heads/strub)] drop va_list from formals if requested

[gcc(refs/users/aoliva/heads/strub)] drop va_list from formals if requested

[Alexandre Oliva]

https://gcc.gnu.org/g:dc14bb8d06db69b73e5dfa279db45cdbdf7061df

commit dc14bb8d06db69b73e5dfa279db45cdbdf7061df
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Wed Sep 8 19:13:35 2021 -0300

    drop va_list from formals if requested
    
    I'm working on a feature that involves creating wrappers for some
    functions, using alternate means to pass variable argument lists to
    the wrapped versions.  The split-out (wrapped) function shouldn't be
    stdarg, and though comments in m_always_copy_start in
    ipa_param_adjustments suggested that making it negative would cause
    variable arguments to be dropped, this was not the case, and AFAICT
    there was no way to accomplish that.
    
    Perhaps there was no such intent implied by the comments, but that
    sounded like a reasonable plan to me, so I went ahead an implemented
    it.  With this patch, a negative m_always_copy_start drops the
    variable argument list marker from a cloned function's type, and the
    stdarg flag from the cloned cfun data structure.
    
    
    for  gcc/ChangeLog
    
            * ipa-param-manipulation.c (build_adjusted_function_type): Add
            skip_valist, obey it.
            (ipa_param_adjustments::build_new_function_type): Take
            negative m_always_copy_start as skip_valist.
            (ipa_param_body_adjustmnets::modify_formal_parameters):
            Likewise.
            * tree-inline.c (initialize_cfun): Clear stdarg if function
            type doesn't support it.
            * ipa-strub.c (pass_ipa_strub::execute): Check that stdarg is
            dropped from the clone.

Diff:
---
 gcc/ipa-param-manipulation.cc | 15 ++++++++++-----
 gcc/ipa-strub.cc              |  2 ++
 gcc/tree-inline.cc            |  2 +-
 3 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/gcc/ipa-param-manipulation.cc b/gcc/ipa-param-manipulation.cc
index 38328c3e8d0..5c2d1eb88da 100644
--- a/gcc/ipa-param-manipulation.cc
+++ b/gcc/ipa-param-manipulation.cc
@@ -314,14 +314,16 @@ drop_type_attribute_if_params_changed_p (tree name)
 static tree
 build_adjusted_function_type (tree orig_type, vec<tree> *new_param_types,
 			      bool method2func, bool skip_return,
-			      bool args_modified)
+			      bool skip_valist, bool args_modified)
 {
   tree new_arg_types = NULL;
   if (TYPE_ARG_TYPES (orig_type))
     {
       gcc_checking_assert (new_param_types);
-      bool last_parm_void = (TREE_VALUE (tree_last (TYPE_ARG_TYPES (orig_type)))
-			     == void_type_node);
+      bool last_parm_void = (skip_valist
+			     || (TREE_VALUE (tree_last (TYPE_ARG_TYPES
+							(orig_type)))
+				 == void_type_node));
       unsigned len = new_param_types->length ();
       for (unsigned i = 0; i < len; i++)
 	new_arg_types = tree_cons (NULL_TREE, (*new_param_types)[i],
@@ -548,10 +550,11 @@ ipa_param_adjustments::build_new_function_type (tree old_type,
 	  || get_original_index (index) != (int)index)
 	modified = true;
 
+  bool skip_valist = m_always_copy_start < 0;
 
   return build_adjusted_function_type (old_type, new_param_types_p,
 				       method2func_p (old_type), m_skip_return,
-				       modified);
+				       skip_valist, modified);
 }
 
 /* Build variant of function decl ORIG_DECL which has no return value if
@@ -1571,8 +1574,10 @@ ipa_param_body_adjustments::modify_formal_parameters ()
      through tree_function_versioning, not when modifying function body
      directly.  */
   gcc_assert (!m_adjustments || !m_adjustments->m_skip_return);
+  bool skip_valist = m_adjustments && m_adjustments->m_always_copy_start < 0;
   tree new_type = build_adjusted_function_type (orig_type, &m_new_types,
-						m_method2func, false, modified);
+						m_method2func, false,
+						skip_valist, modified);
 
   TREE_TYPE (m_fndecl) = new_type;
   DECL_VIRTUAL_P (m_fndecl) = 0;
diff --git a/gcc/ipa-strub.cc b/gcc/ipa-strub.cc
index 1592e24e2b9..b161a837461 100644
--- a/gcc/ipa-strub.cc
+++ b/gcc/ipa-strub.cc
@@ -2688,6 +2688,8 @@ pass_ipa_strub::execute (function *)
     if (onode->calls_comdat_local)
       nnode->add_to_same_comdat_group (onode);
 
+    gcc_checking_assert (!DECL_STRUCT_FUNCTION (nnode->decl)->stdarg);
+
     set_strub_mode_to (onode, STRUB_WRAPPER);
     set_strub_mode_to (nnode, STRUB_WRAPPED);
 
diff --git a/gcc/tree-inline.cc b/gcc/tree-inline.cc
index 29bb758b7bc..467c3b56245 100644
--- a/gcc/tree-inline.cc
+++ b/gcc/tree-inline.cc
@@ -2820,7 +2820,7 @@ initialize_cfun (tree new_fndecl, tree callee_fndecl, profile_count count)
   cfun->va_list_fpr_size = src_cfun->va_list_fpr_size;
   cfun->has_nonlocal_label = src_cfun->has_nonlocal_label;
   cfun->calls_eh_return = src_cfun->calls_eh_return;
-  cfun->stdarg = src_cfun->stdarg;
+  cfun->stdarg = src_cfun->stdarg && stdarg_p (TREE_TYPE (new_fndecl));
   cfun->after_inlining = src_cfun->after_inlining;
   cfun->can_throw_non_call_exceptions
     = src_cfun->can_throw_non_call_exceptions;