On Mon, Nov 26, 2012 at 3:26 AM, Richard Sandiford
<rdsandif...@googlemail.com> wrote:
> David Edelsohn <dje....@gmail.com> writes:
>> I have been working to enable native thread-local storage on AIX. One
>> problem I encountered is the AIX assembler has difficulty with the
>> anchor symbol for TLS CSECTs. While the section anchors machinery
>> uses a separate pool for TLS entries, should section anchor blocks be
>> used for TLS symbols at all?
>>
>> powerpc-linux uses GOT annotations directly and never places TLS
>> symbols in the TOC at all. Section anchors seem to be avoided by TLS
>> code already. The appended patch rejects TLS symbols for object
>> blocks in general. I could add a target hook, but I wanted to propose
>> this policy in general before pursing a target-specific hook.
>
> Yeah, TLS anchors "work" on mips64-linux-gnu, although admittedly
> section anchors aren't yet enabled by default there, so perhaps not
> many people have tried it.
I know that it *CAN* work. Part of my question was whether
thread-local symbols *SHOULD* be placed in section anchor blocks,
whether or not they can be placed there on some systems.
> A use_blocks_for_decl_p hook sounds good, and fits nicely with
> targetm.use_blocks_for_constant_p.
Below is the implementation as a new target hook.
Thanks, David
* target.def (use_blocks_for_decl_p): New hook.
* varasm.c (use_blocks_for_decl_p): Apply hook as final condition.
Index: target.def
===================================================================
--- target.def (revision 193798)
+++ target.def (working copy)
@@ -1495,6 +1495,13 @@
bool, (enum machine_mode mode, const_rtx x),
hook_bool_mode_const_rtx_false)
+/* True if the given decl can be put into an object_block. */
+DEFHOOK
+(use_blocks_for_decl_p,
+ "",
+ bool, (const_tree decl),
+ hook_bool_const_tree_true)
+
/* The minimum and maximum byte offsets for anchored addresses. */
DEFHOOKPOD
(min_anchor_offset,
Index: varasm.c
===================================================================
--- varasm.c (revision 193798)
+++ varasm.c (working copy)
@@ -1113,7 +1113,7 @@
if (lookup_attribute ("alias", DECL_ATTRIBUTES (decl)))
return false;
- return true;
+ return targetm.use_blocks_for_decl_p (decl);
}
/* Create the DECL_RTL for a VAR_DECL or FUNCTION_DECL. DECL should
