On 05.01.17 13:05, Richard Biener wrote:
On Wed, 4 Jan 2017, Andreas Tobler wrote:
On 04.01.17 10:21, Richard Biener wrote:
On Wed, 28 Dec 2016, Andreas Tobler wrote:
On 28.12.16 19:24, Richard Biener wrote:
On December 27, 2016 11:17:00 PM GMT+01:00, Andreas Tobler
<andreast-l...@fgznet.ch> wrote:
On 16.09.16 13:30, Richard Biener wrote:
On Thu, 15 Sep 2016, Richard Biener wrote:
This addresses sth I needed to address with the early LTO debug
patches
(you might now figure I'm piecemail merging stuff from that
patch).
When the cgraph code optimizes out a global we call the
late_global_decl
debug hook to eventually add a DW_AT_const_value to its DIE (we
don't
really expect a location as that will be invalid after optimizing
out
and will be pruned).
With the early LTO debug patches I have introduced a
early_dwarf_finished
flag (mainly for consistency checking) and I figured I can use
that
to
detect the call to the late hook during the early phase and
provide
the following cleaned up variant of avoiding to create locations
that
require later pruning (which doesn't work with emitting the early
DIEs).
Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
I verified it does the correct thing for a unit like
static const int i = 2;
(but ISTR we do have at least one testcase in the testsuite as
well).
Will commit if testing finishes successfully.
Ok, so it showed issues when merging that back to early-LTO-debug.
Turns out in LTO we never call early_finish and thus
early_dwarf_finished
was never set. Also dwarf2out_late_global_decl itself is a better
place to constrain generating locations.
The following variant is in very late stage of testing.
Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
LTO bootstrap on x86_64-unknown-linux-gnu in stage3. LTO bootstrap
with early-LTO-debug in stage3, bootstraped with early-LTO-debug,
testing in progress.
Any chance to backport this commit (r240228) to 6.x?
It fixes a bootstrap comparison issue on aarch64-*-freebsd*.
The aarch64-*-freebsd* port is not yet merged to 6.x and 5.4.x due to
the bootstrap comparison failure I faced.
Did you analyze the bootstrap miscompare? I suspect the patch merely
papers
over the problem.
gcc/contrib/compare-debug -p prev-gcc/ipa-icf.o gcc/ipa-icf.o
prev-gcc/ipa-icf.o.stripped. gcc/ipa-icf.o.stripped. differ: char 52841,
line
253
The objdump -dSx diff on the non stripped object looked always more or
less
the same, a rodata offset which was different.
- 1448: R_AARCH64_ADD_ABS_LO12_NC .rodata+0x1d8
+ 1448: R_AARCH64_ADD_ABS_LO12_NC .rodata+0x410
Hmm, sounds like a constant pool entry was created by -g at a different
time (and thus offset) from regular compilation. So yes, the patch
in question should have the affect to "fix" this.
Note that I later changed the fix with
2016-10-20 Richard Biener <rguent...@suse.de>
* cgraphunit.c (analyze_functions): Set node->definition to
false to signal symbol removal to debug_hooks->late_global_decl.
* ipa.c (symbol_table::remove_unreachable_nodes): When not in
WPA signal symbol removal to the debuginfo machinery.
* dwarf2out.c (dwarf2out_late_global_decl): Instead of
using early_finised to guard the we're called for symbol
removal case look at the symtabs definition flag.
(gen_variable_die): Remove redundant check.
(the dwarf2out_late_global_decl and analyze_functions part are
relevant).
That should be the fix to backport (avoiding the early_dwarf_finished
part).
Ok, I bootstrapped with the attached snippet (had to tweak a bit to apply
cleanly). w/o the previous mentioned fix (r240228). Is this what you had in
mind or do you think some parts of the other fix (r240228) is also needed?
Not sure if you need the dwarf2out.c part you included but you clearly
missed the dwarf2out_late_global_decl part doing
/* We get called via the symtab code invoking late_global_decl
for symbols that are optimized out. Do not add locations
for those. */
varpool_node *node = varpool_node::get (decl);
if (! node || ! node->definition)
tree_add_const_value_attribute_for_decl (die, decl);
else
add_location_or_const_value_attribute (die, decl, false);
I wouldn't include the ipa.c part unless required (it adds additional
debug for optimized out decls).
Ok, attached the part I bootstrapped successfully on amd64-*-freebsd12
and aarch64-*-freebsd12. From the amd64 run you'll find some test
results at the usual place. The aarch64 run takes some more time.
I hope I got it right this time :)
What do you think?
Thanks,
Andreas
Index: dwarf2out.c
===================================================================
--- dwarf2out.c (revision 244100)
+++ dwarf2out.c (working copy)
@@ -23752,7 +23752,17 @@
{
dw_die_ref die = lookup_decl_die (decl);
if (die)
- add_location_or_const_value_attribute (die, decl, false);
+ {
+ /* We get called during the early debug phase via the symtab
+ code invoking late_global_decl for symbols that are optimized
+ out. When the early phase is not finished, do not add
+ locations. */
+ varpool_node *node = varpool_node::get (decl);
+ if (! node || ! node->definition)
+ tree_add_const_value_attribute_for_decl (die, decl);
+ else
+ add_location_or_const_value_attribute (die, decl, false);
+ }
}
}
Index: cgraphunit.c
===================================================================
--- cgraphunit.c (revision 244100)
+++ cgraphunit.c (working copy)
@@ -1193,8 +1193,16 @@
at looking at optimized away DECLs, since
late_global_decl will subsequently be called from the
contents of the now pruned symbol table. */
- if (!decl_function_context (node->decl))
- (*debug_hooks->late_global_decl) (node->decl);
+ if (VAR_P (node->decl)
+ && !decl_function_context (node->decl))
+ {
+ /* We are reclaiming totally unreachable code and variables
+ so they effectively appear as readonly. Show that to
+ the debug machinery. */
+ TREE_READONLY (node->decl) = 1;
+ node->definition = false;
+ (*debug_hooks->late_global_decl) (node->decl);
+ }
node->remove ();
continue;
