[patch v2] Get rid of stack trampolines for nested functions (1/4)
Lynn A. Boger
laboger@linux.vnet.ibm.com
Mon Dec 5 21:29:00 GMT 2016
I think you mean https://github.com/golang/go/issues/18200.
- Lynn
On 12/05/2016 02:52 PM, Ian Lance Taylor wrote:
> On Sun, Sep 4, 2016 at 1:10 PM, Eric Botcazou <ebotcazou@adacore.com> wrote:
>> 2016-07-04 Eric Botcazou <ebotcazou@adacore.com>
>>
>> PR ada/37139
>> PR ada/67205
>> * common.opt (-ftrampolines): New option.
>> * doc/invoke.texi (Code Gen Options): Document it.
>> * doc/tm.texi.in (Trampolines): AddTARGET_CUSTOM_FUNCTION_DESCRIPTORS
>> * doc/tm.texi: Regenerate.
>> * builtins.def: Add init_descriptor and adjust_descriptor.
>> * builtins.c (expand_builtin_init_trampoline): Do not issue a warning
>> on platforms with descriptors.
>> (expand_builtin_init_descriptor): New function.
>> (expand_builtin_adjust_descriptor): Likewise.
>> (expand_builtin) <BUILT_IN_INIT_DESCRIPTOR>: New case.
>> <BUILT_IN_ADJUST_DESCRIPTOR>: Likewise.
>> * calls.c (prepare_call_address): Remove SIBCALLP parameter and add
>> FLAGS parameter. Deal with indirect calls by descriptor and adjust.
>> Set STATIC_CHAIN_REG_P on the static chain register, if any.
>> (call_expr_flags): Set ECF_BY_DESCRIPTOR for calls by descriptor.
>> (expand_call): Likewise. Move around call to prepare_call_address
>> and pass all flags to it.
>> * cfgexpand.c (expand_call_stmt): Reinstate CALL_EXPR_BY_DESCRIPTOR.
>> * gimple.h (enum gf_mask): New GF_CALL_BY_DESCRIPTOR value.
>> (gimple_call_set_by_descriptor): New setter.
>> (gimple_call_by_descriptor_p): New getter.
>> * gimple.c (gimple_build_call_from_tree): SetCALL_EXPR_BY_DESCRIPTOR.
>> (gimple_call_flags): Deal with GF_CALL_BY_DESCRIPTOR.
>> * langhooks.h (struct lang_hooks): Add custom_function_descriptors.
>> * langhooks-def.h (LANG_HOOKS_CUSTOM_FUNCTION_DESCRIPTORS): Define.
>> (LANG_HOOKS_INITIALIZER): Add LANG_HOOKS_CUSTOM_FUNCTION_DESCRIPTORS.
>> * rtl.h (STATIC_CHAIN_REG_P): New macro.
>> * rtlanal.c (find_first_parameter_load): Skip static chain registers.
>> * target.def (custom_function_descriptors): New POD hook.
>> * tree.h (FUNC_ADDR_BY_DESCRIPTOR): New flag on ADDR_EXPR.
>> (CALL_EXPR_BY_DESCRIPTOR): New flag on CALL_EXPR.
>> * tree-core.h (ECF_BY_DESCRIPTOR): New mask.
>> Document FUNC_ADDR_BY_DESCRIPTOR and CALL_EXPR_BY_DESCRIPTOR.
>> * tree.c (make_node_stat) <tcc_declaration>: Use FUNCTION_ALIGNMENT.
>> (build_common_builtin_nodes): Initialize init_descriptor and
>> adjust_descriptor.
>> * tree-nested.c: Include target.h.
>> (struct nesting_info): Add 'any_descr_created' field.
>> (get_descriptor_type): New function.
>> (lookup_element_for_decl): New function extracted from...
>> (create_field_for_decl): Likewise.
>> (lookup_tramp_for_decl): ...here. Adjust.
>> (lookup_descr_for_decl): New function.
>> (convert_tramp_reference_op): Deal with descriptors.
>> (build_init_call_stmt): New function extracted from...
>> (finalize_nesting_tree_1): ...here. Adjust and deal withdescriptors.
>> * defaults.h (FUNCTION_ALIGNMENT): Define.
>> (TRAMPOLINE_ALIGNMENT): Set to above instead of FUNCTION_BOUNDARY.
> According to https://golang.org/cl/18200, this change broke Go on PPC64le.
>
> I haven't investigated myself and I don't know why. Go does not use
> stack trampolines for function closures. It does use function
> closures, but they are built on the heap. It also uses closures
> mediated by libffi. The Go frontend does not enable custom function
> descriptors.
>
> It should be possible to recreate the problem by configuring with
> --enable-languages=go and running `make
> RUNTESTFLAGS="go-test.exp=recover.go" check-gcc-go`.
>
> Ian
>
>
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