[PATCH v2 07/10] Introduce strub: infrastructure interfaces and adjustments

[Alexandre Oliva <oliva@adacore.com>]

Introduce the new strub passes, adjust other passes and front-end
declaration for strub.

for  gcc/ChangeLog

	* Makefile.in (OBJS): Add ipa-strub.o.
	* ipa-inline.cc: Include ipa-strub.h.
	(can_inline_edge_p): Test strub_inlinable_to_p.
	* ipa-split.cc: Include ipa-strub.h.
	(execute_split_functions): Test strub_splittable_p.
	* ipa-strub.h: New.
	* passes.def: Add strub_mode and strub passes.
	* tree-cfg.cc (gimple_verify_flow_info): Note on debug stmts.
	* tree-pass.h (make_pass_ipa_strub_mode): Declare.
	(make_pass_ipa_strub): Declare.
	(make_pass_ipa_function_and_variable_visibility): Fix
	formatting.
	* tree-ssa-ccp.cc (optimize_stack_restore): Keep restores
	before strub leave.
	* multiple_target.cc (pass_target_clone::gate): Test seen_error.

for  gcc/ada/ChangeLog

	* gcc-interface/trans.cc: Include ipa-strub.h.
	(gigi): Make internal decls for targets of compiler-generated
	calls strub-callable too.
	(build_raise_check): Likewise.

diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index 203f0a15187d2..4100531d73ae7 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -1480,6 +1480,7 @@ OBJS = \
 	ipa-reference.o \
 	ipa-ref.o \
 	ipa-utils.o \
+	ipa-strub.o \
 	ipa.o \
 	ira.o \
 	ira-build.o \
diff --git a/gcc/ada/gcc-interface/trans.cc b/gcc/ada/gcc-interface/trans.cc
index c1dd567b2e4e2..e3553a7a87bfc 100644
--- a/gcc/ada/gcc-interface/trans.cc
+++ b/gcc/ada/gcc-interface/trans.cc
@@ -69,6 +69,21 @@
 #include "ada-tree.h"
 #include "gigi.h"
 
+/* The following #include is for strub_make_callable.
+
+   This function marks a function as safe to call from strub contexts.  We mark
+   Ada subprograms that may be called implicitly by the compiler, and that won't
+   leave on the stack caller data passed to them.  This stops implicit calls
+   introduced in subprograms that have their stack scrubbed from being flagged
+   as unsafe, even in -fstrub=strict mode.
+
+   These subprograms are also marked with the strub(callable) attribute in Ada
+   sources, but their declarations aren't necessarily imported by GNAT, or made
+   visible to gigi, in units that end up relying on them.  So when gigi
+   introduces their declarations on its own, it must also add the attribute, by
+   calling strub_make_callable.  */
+#include "ipa-strub.h"
+
 /* We should avoid allocating more than ALLOCA_THRESHOLD bytes via alloca,
    for fear of running out of stack space.  If we need more, we use xmalloc
    instead.  */
@@ -449,6 +464,7 @@ gigi (Node_Id gnat_root,
 						     int64_type, NULL_TREE),
 			   NULL_TREE, is_default, true, true, true, false,
 			   false, NULL, Empty);
+  strub_make_callable (mulv64_decl);
 
   if (Enable_128bit_Types)
     {
@@ -461,6 +477,7 @@ gigi (Node_Id gnat_root,
 							 NULL_TREE),
 			       NULL_TREE, is_default, true, true, true, false,
 			       false, NULL, Empty);
+      strub_make_callable (mulv128_decl);
     }
 
   /* Name of the _Parent field in tagged record types.  */
@@ -716,6 +733,7 @@ build_raise_check (int check, enum exception_info_kind kind)
     = create_subprog_decl (get_identifier (Name_Buffer), NULL_TREE, ftype,
 			   NULL_TREE, is_default, true, true, true, false,
 			   false, NULL, Empty);
+  strub_make_callable (result);
 
   return result;
 }
diff --git a/gcc/ipa-inline.cc b/gcc/ipa-inline.cc
index 14969198cde1c..0674fe138574d 100644
--- a/gcc/ipa-inline.cc
+++ b/gcc/ipa-inline.cc
@@ -119,6 +119,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "stringpool.h"
 #include "attribs.h"
 #include "asan.h"
+#include "ipa-strub.h"
 
 typedef fibonacci_heap <sreal, cgraph_edge> edge_heap_t;
 typedef fibonacci_node <sreal, cgraph_edge> edge_heap_node_t;
@@ -397,6 +398,11 @@ can_inline_edge_p (struct cgraph_edge *e, bool report,
       inlinable = false;
     }
 
+  if (inlinable && !strub_inlinable_to_p (callee, caller))
+    {
+      e->inline_failed = CIF_UNSPECIFIED;
+      inlinable = false;
+    }
   if (!inlinable && report)
     report_inline_failed_reason (e);
   return inlinable;
diff --git a/gcc/ipa-split.cc b/gcc/ipa-split.cc
index 16734617d0381..b3b9963f13669 100644
--- a/gcc/ipa-split.cc
+++ b/gcc/ipa-split.cc
@@ -104,6 +104,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "ipa-fnsummary.h"
 #include "cfgloop.h"
 #include "attribs.h"
+#include "ipa-strub.h"
 
 /* Per basic block info.  */
 
@@ -1810,6 +1811,12 @@ execute_split_functions (void)
 		 "section.\n");
       return 0;
     }
+  if (!strub_splittable_p (node))
+    {
+      if (dump_file)
+	fprintf (dump_file, "Not splitting: function is a strub context.\n");
+      return 0;
+    }
 
   /* We enforce splitting after loop headers when profile info is not
      available.  */
diff --git a/gcc/ipa-strub.h b/gcc/ipa-strub.h
new file mode 100644
index 0000000000000..29869fadfa6c9
--- /dev/null
+++ b/gcc/ipa-strub.h
@@ -0,0 +1,45 @@
+/* strub (stack scrubbing) infrastructure.
+   Copyright (C) 2021-2022 Free Software Foundation, Inc.
+   Contributed by Alexandre Oliva <oliva@adacore.com>.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+/* Return TRUE if CALLEE can be inlined into CALLER, as far as stack scrubbing
+   constraints are concerned.  CALLEE doesn't have to be called directly by
+   CALLER, but the returned value says nothing about intervening functions.  */
+extern bool strub_inlinable_to_p (cgraph_node *callee, cgraph_node *caller);
+
+/* Return FALSE if NODE is a strub context, and TRUE otherwise.  */
+extern bool strub_splittable_p (cgraph_node *node);
+
+/* Locate and return the watermark_ptr parameter for FNDECL.  If FNDECL is not a
+   strub context, return NULL.  */
+extern tree strub_watermark_parm (tree fndecl);
+
+/* Make a function type or declaration callable.  */
+extern void strub_make_callable (tree fndecl);
+
+/* Return zero iff ID is NOT an acceptable parameter for a user-supplied strub
+   attribute for a function.  Otherwise, return >0 if it enables strub, <0 if it
+   does not.  Return +/-1 if the attribute-modified type is compatible with the
+   type without the attribute, or +/-2 if it is not compatible.  */
+extern int strub_validate_fn_attr_parm (tree id);
+
+/* Like comptypes, return 0 if t1 and t2 are not compatible, 1 if they are
+   compatible, and 2 if they are nearly compatible.  Same strub mode is
+   compatible, interface-compatible strub modes are nearly compatible.  */
+extern int strub_comptypes (tree t1, tree t2);
diff --git a/gcc/multiple_target.cc b/gcc/multiple_target.cc
index 3e2d26882c8e9..7cbd0a571e1ff 100644
--- a/gcc/multiple_target.cc
+++ b/gcc/multiple_target.cc
@@ -536,7 +536,7 @@ public:
 bool
 pass_target_clone::gate (function *)
 {
-  return true;
+  return !seen_error ();
 }
 
 } // anon namespace
diff --git a/gcc/passes.def b/gcc/passes.def
index 6bb92efacd451..513c5c29cd281 100644
--- a/gcc/passes.def
+++ b/gcc/passes.def
@@ -52,6 +52,7 @@ along with GCC; see the file COPYING3.  If not see
   INSERT_PASSES_AFTER (all_small_ipa_passes)
   NEXT_PASS (pass_ipa_free_lang_data);
   NEXT_PASS (pass_ipa_function_and_variable_visibility);
+  NEXT_PASS (pass_ipa_strub_mode);
   NEXT_PASS (pass_build_ssa_passes);
   PUSH_INSERT_PASSES_WITHIN (pass_build_ssa_passes)
       NEXT_PASS (pass_fixup_cfg);
@@ -113,6 +114,7 @@ along with GCC; see the file COPYING3.  If not see
   POP_INSERT_PASSES ()
 
   NEXT_PASS (pass_ipa_remove_symbols);
+  NEXT_PASS (pass_ipa_strub);
   NEXT_PASS (pass_ipa_oacc);
   PUSH_INSERT_PASSES_WITHIN (pass_ipa_oacc)
       NEXT_PASS (pass_ipa_pta);
diff --git a/gcc/tree-cfg.cc b/gcc/tree-cfg.cc
index 5bcf78198e78b..6144b9ee4fca4 100644
--- a/gcc/tree-cfg.cc
+++ b/gcc/tree-cfg.cc
@@ -5658,6 +5658,7 @@ gimple_verify_flow_info (void)
 	{
 	  gimple *stmt = gsi_stmt (gsi);
 
+	  /* Do NOT disregard debug stmts after found_ctrl_stmt.  */
 	  if (found_ctrl_stmt)
 	    {
 	      error ("control flow in the middle of basic block %d",
diff --git a/gcc/tree-pass.h b/gcc/tree-pass.h
index 4dfe05ed8e0de..ecf1f9ef28b12 100644
--- a/gcc/tree-pass.h
+++ b/gcc/tree-pass.h
@@ -502,8 +502,9 @@ extern gimple_opt_pass *make_pass_adjust_alignment (gcc::context *ctxt);
 
 /* IPA Passes */
 extern simple_ipa_opt_pass *make_pass_ipa_lower_emutls (gcc::context *ctxt);
-extern simple_ipa_opt_pass
-							      *make_pass_ipa_function_and_variable_visibility (gcc::context *ctxt);
+extern simple_ipa_opt_pass *make_pass_ipa_function_and_variable_visibility (gcc::context *ctxt);
+extern simple_ipa_opt_pass *make_pass_ipa_strub_mode (gcc::context *ctxt);
+extern simple_ipa_opt_pass *make_pass_ipa_strub (gcc::context *ctxt);
 extern simple_ipa_opt_pass *make_pass_ipa_tree_profile (gcc::context *ctxt);
 extern simple_ipa_opt_pass *make_pass_ipa_auto_profile (gcc::context *ctxt);
 
diff --git a/gcc/tree-ssa-ccp.cc b/gcc/tree-ssa-ccp.cc
index 85c046078249c..8d04e55ba6523 100644
--- a/gcc/tree-ssa-ccp.cc
+++ b/gcc/tree-ssa-ccp.cc
@@ -3054,7 +3054,9 @@ optimize_stack_restore (gimple_stmt_iterator i)
       if (!callee
 	  || !fndecl_built_in_p (callee, BUILT_IN_NORMAL)
 	  /* All regular builtins are ok, just obviously not alloca.  */
-	  || ALLOCA_FUNCTION_CODE_P (DECL_FUNCTION_CODE (callee)))
+	  || ALLOCA_FUNCTION_CODE_P (DECL_FUNCTION_CODE (callee))
+	  /* Do not remove stack updates before strub leave.  */
+	  || fndecl_built_in_p (callee, BUILT_IN___STRUB_LEAVE))
 	return NULL_TREE;
 
       if (fndecl_built_in_p (callee, BUILT_IN_STACK_RESTORE))

-- 
Alexandre Oliva, happy hacker                https://FSFLA.org/blogs/lxo/
   Free Software Activist                       GNU Toolchain Engineer
Disinformation flourishes because many people care deeply about injustice
but very few check the facts.  Ask me about <https://stallmansupport.org>