[PATCH] internal-fn, tree-cfg: Fix .TRAP handling and another __builtin_trap vops issue [PR106099]

[Jakub Jelinek <jakub@redhat.com>]

Hi!

This patch fixes 2 __builtin_unreachable/__builtin_trap related issues.
One (first hunk) is that CDDCE happily removes calls to .TRAP ()
internal-fn as useless.  The problem is that the internal-fn is
ECF_CONST | ECF_NORETURN, doesn't have lhs and so DCE thinks it doesn't
have side-effects and removes it.  __builtin_unreachable which has
the same ECF_* flags works fine, as since PR44485 we implicitly add
ECF_LOOPING_CONST_OR_PURE to ECF_CONST | ECF_NORETURN builtins, but
do it in flags_from_decl_or_type which isn't called for internal-fns.
As IFN_TRAP is the only ifn with such flags, it seems easier to
add it explicitly.

The other issue (which on the testcase can be seen only with the
first bug unfixed) is that execute_fixup_cfg can add a __builtin_trap
which needs vops, but nothing adds it and it can appear in many passes
which don't have corresponding TODO_update_ssa_only_virtuals etc.
Fixed similarly as last time but emitting ifn there instead.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2022-08-24  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/106099
	* internal-fn.def (TRAP): Add ECF_LOOPING_CONST_OR_PURE flag.
	* tree-cfg.cc (execute_fixup_cfg): Add IFN_TRAP instead of
	__builtin_trap to avoid the need of vops.

	* gcc.dg/pr106099.c: New test.

--- gcc/internal-fn.def.jj	2022-07-28 12:43:12.876295553 +0200
+++ gcc/internal-fn.def	2022-08-23 14:21:49.559364691 +0200
@@ -458,7 +458,8 @@ DEF_INTERNAL_FN (SPACESHIP, ECF_CONST |
 
 /* __builtin_trap created from/for __builtin_unreachable.  */
 DEF_INTERNAL_FN (TRAP, ECF_CONST | ECF_LEAF | ECF_NORETURN
-		       | ECF_NOTHROW | ECF_COLD, NULL)
+		       | ECF_NOTHROW | ECF_COLD | ECF_LOOPING_CONST_OR_PURE,
+		 NULL)
 
 #undef DEF_INTERNAL_INT_FN
 #undef DEF_INTERNAL_FLT_FN
--- gcc/tree-cfg.cc.jj	2022-07-26 10:32:23.998267698 +0200
+++ gcc/tree-cfg.cc	2022-08-23 12:36:03.818856327 +0200
@@ -9879,10 +9879,16 @@ execute_fixup_cfg (void)
 	      if (stmt && is_gimple_call (stmt))
 		gimple_call_set_ctrl_altering (stmt, false);
 	      tree fndecl = builtin_decl_unreachable ();
-	      stmt = gimple_build_call (fndecl, 0);
+	      if (DECL_FUNCTION_CODE (fndecl) != BUILT_IN_TRAP)
+		stmt = gimple_build_call (fndecl, 0);
+	      else
+		/* Instead of __builtin_trap use .TRAP, so that it doesn't
+		   need vops.  */
+		stmt = gimple_build_call_internal (IFN_TRAP, 0);
 	      gimple_stmt_iterator gsi = gsi_last_bb (bb);
 	      gsi_insert_after (&gsi, stmt, GSI_NEW_STMT);
-	      if (!cfun->after_inlining)
+	      if (!cfun->after_inlining
+		  && DECL_FUNCTION_CODE (fndecl) != BUILT_IN_TRAP)
 		{
 		  gcall *call_stmt = dyn_cast <gcall *> (stmt);
 		  node->create_edge (cgraph_node::get_create (fndecl),
--- gcc/testsuite/gcc.dg/pr106099.c.jj	2022-08-23 14:30:51.992057144 +0200
+++ gcc/testsuite/gcc.dg/pr106099.c	2022-08-23 14:29:04.271508337 +0200
@@ -0,0 +1,10 @@
+/* PR tree-optimization/106099 */
+/* { dg-do compile } */
+/* { dg-options "-O -fharden-compares -fno-tree-forwprop -fno-tree-ch -fno-tree-dominator-opts -fno-tree-ccp -funreachable-traps --param=scev-max-expr-size=1" } */
+
+void
+foo (void)
+{
+  for (unsigned i = 0; i == 0; i++)
+    __builtin_printf ("%d", i);
+}

	Jakub