GCC Bugzilla Bug 19708

Found when attempting to compile powerpc64-linux glibc using current mainline
gcc,
the attached cut-down testcase results in

tcboff.i: In function 'dummy':
tcboff.i:24: warning: asm operand 0 probably doesn't match constraints
tcboff.i:24: error: impossible constraint in 'asm'

Created an attachment (id=8106) [edit]
testcase

The problem is that we don't fold
"&4294938544B->D.1116.header.multiple_threads" to the offset but 
I remember there was a reason why we don't.

The reason why this works in 3.4.4 is that we "fold' that in the front-end
before getting anywhere.

The easiest fix would be to fold it in the front-end for all INT_CST's like the
following with a slight 
comment fix above:
Index: c-typeck.c
===============================================================
====
RCS file: /cvs/gcc/gcc/gcc/c-typeck.c,v
retrieving revision 1.415
diff -u -p -r1.415 c-typeck.c
--- c-typeck.c  29 Jan 2005 16:12:38 -0000      1.415
+++ c-typeck.c  30 Jan 2005 14:13:00 -0000
@@ -2683,7 +2683,7 @@ build_unary_op (enum tree_code code, tre
         when we have proper support for integer constant expressions.  */
       val = get_base_address (arg);
       if (val && TREE_CODE (val) == INDIRECT_REF
-         && integer_zerop (TREE_OPERAND (val, 0)))
+          && TREE_CODE (TREE_OPERAND (val, 0)) == INTEGER_CST)
        return fold_convert (argtype, fold_offsetof (arg));

       val = build1 (ADDR_EXPR, argtype, arg);

: Search converges between 2004-08-30-trunk (#529) and 2004-08-31-trunk (#530).

Andrew, your patch is wrong; fold_offsetof assumes a zero base.

Alan, I have no particular interest in fixing this.  See how the 
alpha tcb-offsets.def file addresses this same problem.

If this turns out to be Absolutely Necessary, ie affects more than
just the nptl build, we can consider adding more hacks in this area
to accomodate, but at present I just don't think it's worth it.