From patchwork Wed Jun  6 21:04:24 2012
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Subject: don't presume undelegitimized UNSPEC_TLS SYMBOL_REF is a decl
Date: Wed, 06 Jun 2012 11:04:24 -0000
From: Roland McGrath <mcgrathr@google.com>
X-Patchwork-Id: 163427
Message-Id: <x57jhauo6tk7.fsf@frobland.mtv.corp.google.com>
To: Jakub Jelinek <jakub@redhat.com>
Cc: gcc-patches@gcc.gnu.org

cf this change:

	2010-11-19  Jakub Jelinek  <jakub@redhat.com>

		PR target/45870
		* dwarf2out.c (const_ok_for_output_1): Don't complain about
		non-delegitimized TLS UNSPECs.

This case hit me where the rtx was:

	(unspec:SI [
		(symbol_ref:SI ("*.LANCHOR0") [flags 0x1aa])
		(const_int 4 [0x4])
	    ] UNSPEC_TLS)

Note:
1. The UNSPEC has two operands, not one.
2. The SYMBOL_REF does not correspond to any decl.

This corresponds to this ARM code:

		ldr	r3, .L10+4
	...
	.L10:
		<something else>
		.word	.LANCHOR0(tpoff)
	...
		.section	.tdata,"awT",%progbits
		.align	4
	.LANCHOR0 = . + 0
		.type	tdata1, %object
		.size	tdata1, 4
	tdata1:
		.word	1

The only way I know to reproduce this is using a variant ARM target that
I'm still developing and is not yet ready to be submitted, so I don't have
a proper test case to offer.  But I think the principle of the following
change is fairly sound.

What do you think?  (Recall that I am not a GCC committer, so if you like
the change, please commit it for me.)


Thanks,
Roland


2012-06-06  Roland McGrath  <mcgrathr@google.com>

	* dwarf2out.c (const_ok_for_output_1): Detect a TLS UNSPEC using
	SYMBOL_REF_TLS_MODEL rather than DECL_THREAD_LOCAL_P, in case it's
	not a VAR_DECL.  Also don't limit it to UNSPECs with exactly one
	operand.


diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index 6e4ab76..bc68205 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -10129,12 +10129,12 @@ const_ok_for_output_1 (rtx *rtlp, void *data ATTRIBUTE_UNUSED)
 	 we can't express it in the debug info.  */
 #ifdef ENABLE_CHECKING
       /* Don't complain about TLS UNSPECs, those are just too hard to
-	 delegitimize.  */
-      if (XVECLEN (rtl, 0) != 1
+	 delegitimize.  Note this could be a non-decl SYMBOL_REF such as
+	 one in a constant pool entry, so testing SYMBOL_REF_TLS_MODEL
+	 rather than DECL_THREAD_LOCAL_P is not just an optimization.  */
+      if (XVECLEN (rtl, 0) == 0
 	  || GET_CODE (XVECEXP (rtl, 0, 0)) != SYMBOL_REF
-	  || SYMBOL_REF_DECL (XVECEXP (rtl, 0, 0)) == NULL
-	  || TREE_CODE (SYMBOL_REF_DECL (XVECEXP (rtl, 0, 0))) != VAR_DECL
-	  || !DECL_THREAD_LOCAL_P (SYMBOL_REF_DECL (XVECEXP (rtl, 0, 0))))
+	  || SYMBOL_REF_TLS_MODEL (XVECEXP (rtl, 0, 0)) == TLS_MODEL_NONE)
 	inform (current_function_decl
 		? DECL_SOURCE_LOCATION (current_function_decl)
 		: UNKNOWN_LOCATION,