Avoid -Wuninitialized false negatives with sanitization and VLAs.

Resolves:
PR tree-optimization/93100 - gcc -fsanitize=address inhibits -Wuninitialized
PR middle-end/98583 - missing -Wuninitialized reading from a second VLA in its own block

gcc/ChangeLog:

	PR tree-optimization/93100
	PR middle-end/98583
	* tree-ssa-uninit.c (check_defs): Exclude intrinsic functions that
	don't modify referenced objects.

gcc/testsuite/ChangeLog:

	PR tree-optimization/93100
	PR middle-end/98583
	* g++.dg/warn/uninit-pr93100.C: New test.
	* gcc.dg/uninit-pr93100.c: New test.
	* gcc.dg/uninit-pr98583.c: New test.

1 files changed, 11 insertions, 0 deletions

diff --git a/gcc/tree-ssa-uninit.c b/gcc/tree-ssa-uninit.c
index 0800f59..f55ce19 100644
--- a/gcc/tree-ssa-uninit.c
+++ b/gcc/tree-ssa-uninit.c
@@ -209,6 +209,16 @@ check_defs (ao_ref *ref, tree vdef, void *data_)
 {
   check_defs_data *data = (check_defs_data *)data_;
   gimple *def_stmt = SSA_NAME_DEF_STMT (vdef);
+
+  /* The ASAN_MARK intrinsic doesn't modify the variable.  */
+  if (is_gimple_call (def_stmt)
+      && gimple_call_internal_p (def_stmt, IFN_ASAN_MARK))
+    return false;
+
+  /* End of VLA scope is not a kill.  */
+  if (gimple_call_builtin_p (def_stmt, BUILT_IN_STACK_RESTORE))
+    return false;
+
   /* If this is a clobber then if it is not a kill walk past it.  */
   if (gimple_clobber_p (def_stmt))
     {
@@ -216,6 +226,7 @@ check_defs (ao_ref *ref, tree vdef, void *data_)
 	return true;
       return false;
     }
+
   /* Found a may-def on this path.  */
   data->found_may_defs = true;
   return true;