[PATCH] Adjust volatile handling of the operand scanner

[PATCH] Adjust volatile handling of the operand scanner

[Richard Biener]

The GIMPLE SSA operand scanner handles COMPONENT_REFs that are
not marked TREE_THIS_VOLATILE but have a TREE_THIS_VOLATILE
FIELD_DECL as volatile.  That's inconsistent in how TREE_THIS_VOLATILE
testing on GENERIC refs works which requires operand zero of
component references to mirror TREE_THIS_VOLATILE to the ref
so that testing TREE_THIS_VOLATILE on the outermost reference
is enough to determine the volatileness.

The following patch thus removes FIELD_DECL scanning from
the GIMPLE SSA operand scanner, possibly leaving fewer stmts
marked as gimple_has_volatile_ops.

Bootstrap and regtest running on x86_64-unknown-linux-gnu
(ontop of the earlier posted tree-nested fix)

2021-08-09  Richard Biener  <rguenther@suse.de>

	* tree-ssa-operands.c (operands_scanner::get_expr_operands):
	Do not look at COMPONENT_REF FIELD_DECLs TREE_THIS_VOLATILE
	to determine has_volatile_ops.
---
 gcc/tree-ssa-operands.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/gcc/tree-ssa-operands.c b/gcc/tree-ssa-operands.c
index c15575416dd..ebf7eea3b04 100644
--- a/gcc/tree-ssa-operands.c
+++ b/gcc/tree-ssa-operands.c
@@ -834,12 +834,7 @@ operands_scanner::get_expr_operands (tree *expr_p, int flags)
 	get_expr_operands (&TREE_OPERAND (expr, 0), flags);
 
 	if (code == COMPONENT_REF)
-	  {
-	    if (!(flags & opf_no_vops)
-		&& TREE_THIS_VOLATILE (TREE_OPERAND (expr, 1)))
-	      gimple_set_has_volatile_ops (stmt, true);
-	    get_expr_operands (&TREE_OPERAND (expr, 2), uflags);
-	  }
+	  get_expr_operands (&TREE_OPERAND (expr, 2), uflags);
 	else if (code == ARRAY_REF || code == ARRAY_RANGE_REF)
 	  {
 	    get_expr_operands (&TREE_OPERAND (expr, 1), uflags);
-- 
2.31.1