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Handle DW_OP_form_tls_address

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Currently gdb supports DW_OP_GNU_push_tls_address, but not
DW_OP_form_tls_address.  I think it would be better if the toolchain
as a whole moved to using the standard opcode, and the prerequisite to
this is getting gdb to recognize it.

GCC can sometimes emit DW_OP_form_tls_address for emultls targets.  As
far as I know, nobody has ever tried this with gdb (since it wouldn't
work at all).

I don't think there's a major drawback to using a single opcode for
all targets, because computing the location of a thread-local is
already target specific.

This is PR gdb/11616.

I don't know how to write a test case for this; though it's worth
noting that there aren't explicit tests for DW_OP_GNU_push_tls_address
either -- and if I change GCC, these paths will be tested to the same
extent they are now.

2016-09-02  Tom Tromey  <tom@tromey.com>

	PR gdb/11616:
	* dwarf2read.c (decode_locdesc): Handle DW_OP_form_tls_address.
	* dwarf2loc.c (dwarf2_compile_expr_to_ax): Handle
	DW_OP_form_tls_address.
	(locexpr_describe_location_piece): Likewise.
	* dwarf2expr.h (struct dwarf_expr_context_funcs): Update comment.
	* dwarf2expr.c (execute_stack_op): Handle DW_OP_form_tls_address.
	(ctx_no_get_tls_address): Mention DW_OP_form_tls_address.
	* compile/compile-loc2c.c (struct insn_info): Update comment.
	(compute_stack_depth_worker): Handle DW_OP_form_tls_address.
This commit is contained in:
Tom Tromey 2016-08-22 16:56:52 -06:00
parent 1b2d85b255
commit 4aa4e28bdc
6 changed files with 26 additions and 7 deletions
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7
gdb/compile/compile-loc2c.c
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@ -48,9 +48,9 @@ struct insn_info
unsigned int label : 1;
/* Whether this instruction is DW_OP_GNU_push_tls_address. This is
a hack until we can add a feature to glibc to let us properly
generate code for TLS. */
/* Whether this instruction is DW_OP_GNU_push_tls_address or
DW_OP_form_tls_address. This is a hack until we can add a
feature to glibc to let us properly generate code for TLS. */
unsigned int is_tls : 1;
};
@ -323,6 +323,7 @@ compute_stack_depth_worker (int start, int *need_tempvar,
break;
case DW_OP_GNU_push_tls_address:
case DW_OP_form_tls_address:
info[ndx].is_tls = 1;
break;