Hi!
The following testcase is rejected, while it was accepted in 3.4 and earlier
(before tree-ssa merge).
The problem is that we decide to promote the const variable to TREE_STATIC,
but TREE_STATIC DECL_REGISTER VAR_DECLs may only be the global register vars
and so assemble_variable/make_decl_rtl diagnoses it.
Either we do what the following patch does, where we could consider
register as a hint the user doesn't want such optimization, because if
something is forced static, it is not "register" anymore and register static
is not valid in C either, or we could clear DECL_REGISTER instead, but would
still need to punt at least on DECL_HARD_REGISTER cases.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2020-02-27 Jakub Jelinek <ja...@redhat.com>
PR c/93949
* gimplify.c (gimplify_init_constructor): Don't promote readonly
DECL_REGISTER variables to TREE_STATIC.
* gcc.c-torture/compile/pr93949.c: New test.
--- gcc/gimplify.c.jj 2020-02-25 13:54:02.087091120 +0100
+++ gcc/gimplify.c 2020-02-26 19:30:57.466490166 +0100
@@ -4923,6 +4923,7 @@ gimplify_init_constructor (tree *expr_p,
&& num_nonzero_elements > 1
&& TREE_READONLY (object)
&& VAR_P (object)
+ && !DECL_REGISTER (object)
&& (flag_merge_constants >= 2 || !TREE_ADDRESSABLE (object))
/* For ctors that have many repeated nonzero elements
represented through RANGE_EXPRs, prefer initializing
--- gcc/testsuite/gcc.c-torture/compile/pr93949.c.jj 2020-02-26
19:42:15.754530691 +0100
+++ gcc/testsuite/gcc.c-torture/compile/pr93949.c 2020-02-26
19:42:08.153642329 +0100
@@ -0,0 +1,7 @@
+/* PR c/93949 */
+
+void
+foo (void)
+{
+ register const double d[3] = { 0., 1., 2. };
+}
Jakub
