The PR complains that we fail to properly initialize a
volatile struct with a single assignment if the initializer
is all-zeros.
Fixed as follows.
Bootstrap / regtest running on x86_64-unknown-linux-gnu.
Richard.
2019-07-10 Richard Biener <rguent...@suse.de>
PR middle-end/91131
* gimplify.c (gimplify_compound_literal_expr): Force a temporary
when the object is volatile and we have not cleared it even though
there are no nonzero elements.
* gcc.target/i386/pr91131.c: New testcase.
Index: gcc/gimplify.c
===================================================================
--- gcc/gimplify.c (revision 273355)
+++ gcc/gimplify.c (working copy)
@@ -5005,7 +5004,7 @@ gimplify_init_constructor (tree *expr_p,
one field to assign, initialize the target from a temporary. */
if (TREE_THIS_VOLATILE (object)
&& !TREE_ADDRESSABLE (type)
- && num_nonzero_elements > 0
+ && (num_nonzero_elements > 0 || !cleared)
&& vec_safe_length (elts) > 1)
{
tree temp = create_tmp_var (TYPE_MAIN_VARIANT (type));
Index: gcc/testsuite/gcc.target/i386/pr91131.c
===================================================================
--- gcc/testsuite/gcc.target/i386/pr91131.c (nonexistent)
+++ gcc/testsuite/gcc.target/i386/pr91131.c (working copy)
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+/* { dg-options "-O" } */
+
+struct Reg_T {
+ unsigned int a : 3;
+ unsigned int b : 1;
+ unsigned int c : 4;
+};
+
+volatile struct Reg_T Reg_A;
+
+int
+main ()
+{
+ Reg_A = (struct Reg_T){ .a = 0, .b = 0, .c = 0 };
+ return 0;
+}
+
+/* { dg-final { scan-assembler-times "mov\[^\r\n\]*Reg_A" 1 } } */
