[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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