[gcc(refs/users/aoliva/heads/testme)] hardcfr: prevent deferred sets of visited bitmap

[Alexandre Oliva <aoliva@gcc.gnu.org>]

https://gcc.gnu.org/g:12d0b287d4ae77cd70604451214965a0f03fd9ca

commit 12d0b287d4ae77cd70604451214965a0f03fd9ca
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Wed Oct 19 20:36:28 2022 -0300

    hardcfr: prevent deferred sets of visited bitmap
    
    Force bitmap sets to hit memory, preventing deferral and likely
    combinations.
    
    
    for  gcc/ChangeLog
    
            * gimple-harden-control-flow.cc (rt_bb_visited::vset): Prevent
            deferral of bitmap sets.

Diff:
---
 gcc/gimple-harden-control-flow.cc | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/gcc/gimple-harden-control-flow.cc b/gcc/gimple-harden-control-flow.cc
index 1ea47615cd4..862cdd45eaf 100644
--- a/gcc/gimple-harden-control-flow.cc
+++ b/gcc/gimple-harden-control-flow.cc
@@ -545,6 +545,19 @@ class rt_bb_visited
     gassign *vstore = gimple_build_assign (unshare_expr (setme), temp);
     gimple_seq_add_stmt (&seq, vstore);
 
+    /* Prevent stores into visited from being deferred, without
+       forcing subsequent bitsets to reload the word.  */
+    vec<tree, va_gc> *inputs = NULL;
+    vec<tree, va_gc> *outputs = NULL;
+    vec_safe_push (inputs,
+		   build_tree_list
+		   (build_tree_list
+		    (NULL_TREE, build_string (1, "m")),
+		    visited));
+    gasm *stabilize = gimple_build_asm_vec ("", inputs, outputs,
+					    NULL, NULL);
+    gimple_seq_add_stmt (&seq, stabilize);
+
     return seq;
   }