On January 12, 2018 4:52:27 PM GMT+01:00, Jakub Jelinek <ja...@redhat.com>
wrote:
>Hi!
>
>The LTO debug changes create a DW_TAG_subprogram in main in one spot
>and
>a small DW_TAG_subprogram that has DW_AT_abstract_origin to that +
>DW_AT_ranges when doing hot/cold partitioning. Unfortunately, it seems
>GDB
>in that case doesn't read the DIE in the initial debug info read, as
>read_partial_die only handles DW_AT_{low,high}_pc.
>
>The following patch is an ugly workaround for that, I hope most of
>real-world programs don't have most of the performance sensitive code
>directly in main and so disabling hot/cold partitioning for main if in
>lto
>might be acceptable.
>
>Bootstrapped/regtested on x86_64-linux and i686-linux, fixes:
>-FAIL: gcc.dg/guality/pr43051-1.c -O2 -flto -fno-use-linker-plugin
>-flto-partition=none line 34 c == &a[0]
>-FAIL: gcc.dg/guality/pr43051-1.c -O2 -flto -fno-use-linker-plugin
>-flto-partition=none line 36 e == &a[1]
>-FAIL: gcc.dg/guality/pr43051-1.c -O2 -flto -fno-use-linker-plugin
>-flto-partition=none line 39 c == &a[0]
>-FAIL: gcc.dg/guality/pr43051-1.c -O2 -flto -fno-use-linker-plugin
>-flto-partition=none line 41 e == &a[1]
>-FAIL: gcc.dg/guality/pr43051-1.c -O2 -flto -fuse-linker-plugin
>-fno-fat-lto-objects line 34 c == &a[0]
>-FAIL: gcc.dg/guality/pr43051-1.c -O2 -flto -fuse-linker-plugin
>-fno-fat-lto-objects line 36 e == &a[1]
>-FAIL: gcc.dg/guality/pr43051-1.c -O2 -flto -fuse-linker-plugin
>-fno-fat-lto-objects line 39 c == &a[0]
>-FAIL: gcc.dg/guality/pr43051-1.c -O2 -flto -fuse-linker-plugin
>-fno-fat-lto-objects line 41 e == &a[1]
>-FAIL: gcc.dg/guality/pr45882.c -O2 -flto -fno-use-linker-plugin
>-flto-partition=none line 16 b == 7
>-FAIL: gcc.dg/guality/pr45882.c -O2 -flto -fno-use-linker-plugin
>-flto-partition=none line 16 c == 11
>-FAIL: gcc.dg/guality/pr45882.c -O2 -flto -fno-use-linker-plugin
>-flto-partition=none line 16 d == 112
>-FAIL: gcc.dg/guality/pr45882.c -O2 -flto -fno-use-linker-plugin
>-flto-partition=none line 16 e == 142
>-FAIL: gcc.dg/guality/pr45882.c -O2 -flto -fuse-linker-plugin
>-fno-fat-lto-objects line 16 b == 7
>-FAIL: gcc.dg/guality/pr45882.c -O2 -flto -fuse-linker-plugin
>-fno-fat-lto-objects line 16 c == 11
>Ok for trunk?
OK.
Hopefully this can be fixed in gdb for the upcoming release.
Richard.
>2018-01-12 Jakub Jelinek <ja...@redhat.com>
>
> PR debug/81155
> * bb-reorder.c (pass_partition_blocks::gate): In lto don't partition
> main to workaround a bug in GDB.
>
>--- gcc/bb-reorder.c.jj 2018-01-10 17:08:56.074912734 +0100
>+++ gcc/bb-reorder.c 2018-01-12 11:52:00.936332511 +0100
>@@ -2873,7 +2873,10 @@ pass_partition_blocks::gate (function *f
> we are going to omit the reordering. */
> && optimize_function_for_speed_p (fun)
> && !DECL_COMDAT_GROUP (current_function_decl)
>- && !lookup_attribute ("section", DECL_ATTRIBUTES (fun->decl)));
>+ && !lookup_attribute ("section", DECL_ATTRIBUTES (fun->decl))
>+ /* Workaround a bug in GDB where read_partial_die doesn't cope
>+ with DIEs with DW_AT_ranges, see PR81115. */
>+ && !(in_lto_p && MAIN_NAME_P (DECL_NAME (fun->decl))));
> }
>
> unsigned
>
> Jakub
