Re: [PATCH] arm: Fix up arm_override_options_after_change [PR96939]

[Christophe Lyon <christophe.lyon@linaro.org>]

On Tue, 8 Sep 2020 at 10:45, Jakub Jelinek via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Hi!
>
> As mentioned in the PR, the testcase fails to link, because when set_cfun is
> being called on the crc function, arm_override_options_after_change is
> called from set_cfun -> invoke_set_current_function_hook:
>       /* Change optimization options if needed.  */
>       if (optimization_current_node != opts)
>         {
>           optimization_current_node = opts;
>           cl_optimization_restore (&global_options, TREE_OPTIMIZATION (opts));
>         }
> and at that point target_option_default_node actually matches even the
> current state of options, so this means armv7 (or whatever) arch is set as
> arm_active_target, then
>       targetm.set_current_function (fndecl);
> is called later in that function, which because the crc function's
> DECL_FUNCTION_SPECIFIC_TARGET is different from the current one will do:
>   cl_target_option_restore (&global_options, TREE_TARGET_OPTION (new_tree));
> which calls arm_option_restore and sets arm_active_target to armv8-a+crc
> (so far so good).
> Later arm_set_current_function calls:
>   save_restore_target_globals (new_tree);
> which in this case calls:
>       /* Call target_reinit and save the state for TARGET_GLOBALS.  */
>       TREE_TARGET_GLOBALS (new_tree) = save_target_globals_default_opts ();
> which because optimization_current_node != optimization_default_node
> (the testcase is LTO, so all functions have their
> DECL_FUNCTION_SPECIFIC_TARGET and TREE_OPTIMIZATION nodes) will call:
>       cl_optimization_restore
>         (&global_options,
>          TREE_OPTIMIZATION (optimization_default_node));
> and
>       cl_optimization_restore (&global_options,
>                                TREE_OPTIMIZATION (opts));
> The problem is that these call arm_override_options_after_change again,
> and that one uses the target_option_default_node as what to set the
> arm_active_target to (i.e. back to armv7 or whatever, but not to the
> armv8-a+crc that should be the active target for the crc function).
> That means we then error on the builtin call in that function.
>
> Now, the targetm.override_options_after_change hook is called always at the
> end of cl_optimization_restore, i.e. when we change the Optimization marked
> generic options.  So it seems unnecessary to call arm_configure_build_target
> at that point (nothing it depends on changed), and additionally incorrect
> (because it uses the target_option_default_node, rather than the current
> set of options; we'd need to revert
> https://gcc.gnu.org/legacy-ml/gcc-patches/2016-12/msg01390.html
> otherwise so that it works again with global_options otherwise).
> The options that arm_configure_build_target cares about will change only
> during option parsing (which is where it is called already), or during
> arm_set_current_function, where it is done during the
> cl_target_option_restore.
> Now, arm_override_options_after_change_1 wants to adjust the
> str_align_functions, which depends on the current Optimization options (e.g.
> optimize_size and flag_align_options and str_align_functions) as well as
> the target options target_flags, so IMHO needs to be called both
> when the Optimization options (possibly) change, i.e. from
> the targetm.override_options_after_change hook, and from when the target
> options change (set_current_function hook).
>
> Bootstrapped/regtested on armv7hl-linux-gnueabi, ok for trunk?
>
> Looking further at arm_override_options_after_change_1, it also seems to be
> incorrect, rather than testing
> !opts->x_str_align_functions
> it should be really testing
> !opts_set->x_str_align_functions
> and get &global_options_set or similar passed to it as additional opts_set
> argument.  That is because otherwise the decision will be sticky, while it
> should be done whenever use provided -falign-functions but didn't provide
> -falign-functions= (either on the command line, or through optimize
> attribute or pragma).
>
> 2020-09-08  Jakub Jelinek  <jakub@redhat.com>
>
>         PR target/96939
>         * config/arm/arm.c (arm_override_options_after_change): Don't call
>         arm_configure_build_target here.
>         (arm_set_current_function): Call arm_override_options_after_change_1
>         at the end.
>
>         * gcc.target/arm/lto/pr96939_0.c: New test.
>         * gcc.target/arm/lto/pr96939_1.c: New file.
>

Hi Jakub,

I'm seeing an ICE with this new test on most of my arm configurations,
for instance:
--target arm-none-linux-gnueabi --with-cpu cortex-a9
/aci-gcc-fsf/builds/gcc-fsf-gccsrc/obj-arm-none-linux-gnueabi/gcc3/gcc/xgcc
-B/aci-gcc-fsf/builds/gcc-fsf-gccsrc/obj-ar
m-none-linux-gnueabi/gcc3/gcc/ c_lto_pr96939_0.o c_lto_pr96939_1.o
-fdiagnostics-plain-output -flto -O2 -o
gcc-target-arm-lto-pr96939-01.exe
In function 'crc':
lto1: internal compiler error: Segmentation fault
0xba720f crash_signal
        /gcc/toplev.c:327
0x172beb9 strchr
        /usr/include/string.h:227
0x172beb9 arm_parse_cpu_option_name(cpu_option const*, char const*,
char const*, bool)
        /gcc/common/config/arm/arm-common.c:349
0xfa9372 arm_configure_build_target(arm_build_target*,
cl_target_option*, gcc_options*, bool)
        /gcc/config/arm/arm.c:3209
0xfbf8e1 arm_set_current_function
        /gcc/config/arm/arm.c:32334
0x86b68b invoke_set_current_function_hook
        /gcc/function.c:4670
0x870d77 invoke_set_current_function_hook
        /gcc/function.c:4836
0x870d77 allocate_struct_function(tree_node*, bool)
        /gcc/function.c:4793
0xa25943 input_function
        /gcc/lto-streamer-in.c:1385
0xa25943 lto_read_body_or_constructor
        /gcc/lto-streamer-in.c:1624
0x6f37ff cgraph_node::get_untransformed_body()
        /gcc/cgraph.c:3932
0x703f42 cgraph_node::expand()
        /gcc/cgraphunit.c:2274
0x70567c expand_all_functions
        /gcc/cgraphunit.c:2476
0x70567c symbol_table::compile()
        /gcc/cgraphunit.c:2839
0x63970b lto_main()
        /gcc/lto/lto.c:653

This is with a cross-compiler.

Christophe

-
> --- gcc/config/arm/arm.c.jj     2020-07-30 15:04:38.136293101 +0200
> +++ gcc/config/arm/arm.c        2020-09-07 10:43:54.809561852 +0200
> @@ -3037,10 +3037,6 @@ arm_override_options_after_change_1 (str
>  static void
>  arm_override_options_after_change (void)
>  {
> -  arm_configure_build_target (&arm_active_target,
> -                             TREE_TARGET_OPTION (target_option_default_node),
> -                             &global_options_set, false);
> -
>    arm_override_options_after_change_1 (&global_options);
>  }
>
> @@ -32338,6 +32334,8 @@ arm_set_current_function (tree fndecl)
>    cl_target_option_restore (&global_options, TREE_TARGET_OPTION (new_tree));
>
>    save_restore_target_globals (new_tree);
> +
> +  arm_override_options_after_change_1 (&global_options);
>  }
>
>  /* Implement TARGET_OPTION_PRINT.  */
> --- gcc/testsuite/gcc.target/arm/lto/pr96939_0.c.jj     2020-09-07 11:26:45.909937609 +0200
> +++ gcc/testsuite/gcc.target/arm/lto/pr96939_0.c        2020-09-07 11:29:18.722706535 +0200
> @@ -0,0 +1,15 @@
> +/* PR target/96939 */
> +/* { dg-lto-do link } */
> +/* { dg-require-effective-target arm_arch_v8a_ok } */
> +/* { dg-lto-options { { -flto -O2 } } } */
> +
> +extern unsigned crc (unsigned, const void *);
> +typedef unsigned (*fnptr) (unsigned, const void *);
> +volatile fnptr fn;
> +
> +int
> +main ()
> +{
> +  fn = crc;
> +  return 0;
> +}
> --- gcc/testsuite/gcc.target/arm/lto/pr96939_1.c.jj     2020-09-07 11:26:49.365887153 +0200
> +++ gcc/testsuite/gcc.target/arm/lto/pr96939_1.c        2020-09-07 11:25:13.885281180 +0200
> @@ -0,0 +1,10 @@
> +/* PR target/96939 */
> +/* { dg-options "-march=armv8-a+crc" } */
> +
> +#include <arm_acle.h>
> +
> +unsigned
> +crc (unsigned x, const void *y)
> +{
> +  return __crc32cw (x, *(unsigned *) y);
> +}
>
>         Jakub
>