[PATCH] don't presume undelegitimized UNSPEC_TLS SYMBOL_REF is a decl

[Roland McGrath]

cf this change:

        2010-11-19  Jakub Jelinek  <ja...@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  <mcgra...@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,