Hi! Ping.
On Sat, 21 May 2016 17:59:17 +0200, I wrote: > As discussed in <https://gcc.gnu.org/PR70945> "Offloading: compatibility > of target and offloading toolchains", there are situations where we have > to do more work to ensure compatibility between target and offloading > toolchains. > > The first thing I'm working on is math functions usage in offloaded > regions. > > Here is a first patch, addressing glibc's finite math optimizations: if > -ffinite-math-only (as implied by -ffast-math, or -Ofast) is in effect, > glibc's <math.h> is known to include <bits/math-finite.h> for "special > entry points to use when the compiler got told to only expect finite > results". This divertes the math functions' assembler names from > "[function]" to "__[function]_finite". This, obviously, is incompatible > with offloading targets that don't use glibc, and thus don't provide > these "__[function]_finite" entry points. > > In response to Alexander's > <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70945#c3>, I argue this > does belong into the generic offloading data handling, instead of a > nvptx-specific pass, for the reason that it is not a nvptx-specific > transformation but addresses a general target vs. offloading target > configuration mismatch. > > If I understand him correctly, Joseph in > <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70945#c4> confirms my idea > about how this may use some extension (attributes), allowing us to get > rid of the "__[function]_finite" name matching heuristic. That's indeed > something to work on, but as it will take a rather long time until glibc > changes make their way into distributions that end users are using, I'd > like to start with the heuristic as implemented, and adjust this later > on. > > OK for trunk? I'm working on a test case, too. > > commit 0f65dbe65e883d2294c055631eccb07869bc5375 > Author: Thomas Schwinge <tho...@codesourcery.com> > Date: Fri May 13 17:02:30 2016 +0200 > > [PR other/70945] Handle function_glibc_finite_math in offloading > > gcc/ > PR other/70945 > * targhooks.c (default_libc_has_function): Update comment. > * target.def (libc_has_function): Likewise. > * doc/tm.texi: Regenerate. > * coretypes.h (enum function_class): Add > function_glibc_finite_math. > * config/darwin.c (darwin_libc_has_function): Handle it. > * lto-streamer.h (enum lto_section_type): Rename > LTO_section_offload_table to LTO_section_offload_data. Adjust all > users. > * lto-cgraph.c (void output_offload_data): New function, split out > of output_offload_tables. Adjust all users. Stream the target's > function_glibc_finite_math property. > (input_offload_data): New function, split out of > input_offload_tables. Adjust all users. Handle mismatch between > the target's and the offloading target's > function_glibc_finite_math property. > --- > gcc/config/darwin.c | 2 + > gcc/coretypes.h | 11 ++- > gcc/doc/tm.texi | 2 +- > gcc/lto-cgraph.c | 181 > ++++++++++++++++++++++++++++++++++++------------- > gcc/lto-streamer-out.c | 2 +- > gcc/lto-streamer.h | 6 +- > gcc/lto/lto.c | 2 +- > gcc/target.def | 2 +- > gcc/targhooks.c | 2 +- > 9 files changed, 152 insertions(+), 58 deletions(-) > > diff --git gcc/config/darwin.c gcc/config/darwin.c > index 0055d80..92fe3e5 100644 > --- gcc/config/darwin.c > +++ gcc/config/darwin.c > @@ -3401,6 +3401,8 @@ darwin_libc_has_function (enum function_class fn_class) > || fn_class == function_c99_misc) > return (TARGET_64BIT > || strverscmp (darwin_macosx_version_min, "10.3") >= 0); > + if (fn_class == function_glibc_finite_math) > + return false; > > return true; > } > diff --git gcc/coretypes.h gcc/coretypes.h > index b3a91a6..aa48b5a 100644 > --- gcc/coretypes.h > +++ gcc/coretypes.h > @@ -305,14 +305,21 @@ union _dont_use_tree_here_; > > #endif > > -/* Classes of functions that compiler needs to check > +/* Properties, such as classes of functions that the compiler can check > whether they are present at the runtime or not. */ > enum function_class { > function_c94, > function_c99_misc, > function_c99_math_complex, > function_sincos, > - function_c11_misc > + function_c11_misc, > + /* If -ffinite-math-only (as implied by -ffast-math, or -Ofast) is in > effect, > + glibc's <math.h> is known to include <bits/math-finite.h> for "special > + entry points to use when the compiler got told to only expect finite > + results". This divertes the math functions' assembler names from > + "[function]" to "__[function]_finite". This property indicates whether > + such diversion may occur, not whether it actually has. */ > + function_glibc_finite_math > }; > > /* Enumerate visibility settings. This is deliberately ordered from most > diff --git gcc/doc/tm.texi gcc/doc/tm.texi > index 8c7f2a1..4ce3a43 100644 > --- gcc/doc/tm.texi > +++ gcc/doc/tm.texi > @@ -5308,7 +5308,7 @@ macro, a reasonable default is used. > @end defmac > > @deftypefn {Target Hook} bool TARGET_LIBC_HAS_FUNCTION (enum function_class > @var{fn_class}) > -This hook determines whether a function from a class of functions > +This hook determines properties, such as whether a class of functions > @var{fn_class} is present at the runtime. > @end deftypefn > > diff --git gcc/lto-cgraph.c gcc/lto-cgraph.c > index cffa399..4e7aa17 100644 > --- gcc/lto-cgraph.c > +++ gcc/lto-cgraph.c > @@ -38,6 +38,9 @@ along with GCC; see the file COPYING3. If not see > #include "ipa-utils.h" > #include "omp-offload.h" > #include "ipa-chkp.h" > +#include "target.h" > +#include "output.h" > +#include "builtins.h" > > /* True when asm nodes has been output. */ > bool asm_nodes_output = false; > @@ -1094,21 +1097,37 @@ read_string (struct lto_input_block *ib) > return str; > } > > +/* Output offload data. */ > + > +static void output_offload_tables (struct lto_simple_output_block *); > + > +void output_offload_data (void) > +{ > + /* Return early if there is no offload data. */ > + if (vec_safe_is_empty (offload_funcs) && vec_safe_is_empty (offload_vars)) > + return; > + > + struct lto_simple_output_block *ob > + = lto_create_simple_output_block (LTO_section_offload_data); > + > + /* Stream the target's function_glibc_finite_math property. */ > + bool g_f_m = targetm.libc_has_function (function_glibc_finite_math); > + streamer_write_hwi_stream (ob->main_stream, g_f_m); > + > + output_offload_tables (ob); > + > + lto_destroy_simple_output_block (ob); > +} > + > /* Output function/variable tables that will allow libgomp to look up offload > target code. > OFFLOAD_FUNCS is filled in expand_omp_target, OFFLOAD_VARS is filled in > varpool_node::get_create. In WHOPR (partitioned) mode during the WPA > stage > both OFFLOAD_FUNCS and OFFLOAD_VARS are filled by input_offload_tables. > */ > > -void > -output_offload_tables (void) > +static void > +output_offload_tables (struct lto_simple_output_block *ob) > { > - if (vec_safe_is_empty (offload_funcs) && vec_safe_is_empty (offload_vars)) > - return; > - > - struct lto_simple_output_block *ob > - = lto_create_simple_output_block (LTO_section_offload_table); > - > for (unsigned i = 0; i < vec_safe_length (offload_funcs); i++) > { > streamer_write_enum (ob->main_stream, LTO_symtab_tags, > @@ -1126,7 +1145,6 @@ output_offload_tables (void) > } > > streamer_write_uhwi_stream (ob->main_stream, 0); > - lto_destroy_simple_output_block (ob); > > /* In WHOPR mode during the WPA stage the joint offload tables need to be > streamed to one partition only. That's why we free offload_funcs and > @@ -1884,65 +1902,132 @@ input_symtab (void) > } > } > > -/* Input function/variable tables that will allow libgomp to look up offload > - target code, and store them into OFFLOAD_FUNCS and OFFLOAD_VARS. */ > +/* Input offload data. */ > + > +static void input_offload_tables (struct lto_input_block *, > + struct lto_file_decl_data *, bool); > > void > -input_offload_tables (bool do_force_output) > +input_offload_data (bool do_force_output) > { > struct lto_file_decl_data **file_data_vec = lto_get_file_decl_data (); > struct lto_file_decl_data *file_data; > unsigned int j = 0; > + bool g_f_m_target = false; > > while ((file_data = file_data_vec[j++])) > { > const char *data; > size_t len; > struct lto_input_block *ib > - = lto_create_simple_input_block (file_data, LTO_section_offload_table, > + = lto_create_simple_input_block (file_data, LTO_section_offload_data, > &data, &len); > if (!ib) > continue; > > - enum LTO_symtab_tags tag > - = streamer_read_enum (ib, LTO_symtab_tags, LTO_symtab_last_tag); > - while (tag) > - { > - if (tag == LTO_symtab_unavail_node) > - { > - int decl_index = streamer_read_uhwi (ib); > - tree fn_decl > - = lto_file_decl_data_get_fn_decl (file_data, decl_index); > - vec_safe_push (offload_funcs, fn_decl); > + /* Merge the target's function_glibc_finite_math property. */ > + g_f_m_target |= streamer_read_hwi (ib); > > - /* Prevent IPA from removing fn_decl as unreachable, since there > - may be no refs from the parent function to child_fn in offload > - LTO mode. */ > - if (do_force_output) > - cgraph_node::get (fn_decl)->mark_force_output (); > - } > - else if (tag == LTO_symtab_variable) > - { > - int decl_index = streamer_read_uhwi (ib); > - tree var_decl > - = lto_file_decl_data_get_var_decl (file_data, decl_index); > - vec_safe_push (offload_vars, var_decl); > + input_offload_tables (ib, file_data, do_force_output); > > - /* Prevent IPA from removing var_decl as unused, since there > - may be no refs to var_decl in offload LTO mode. */ > - if (do_force_output) > - varpool_node::get (var_decl)->force_output = 1; > - } > - else > - fatal_error (input_location, > - "invalid offload table in %s", file_data->file_name); > - > - tag = streamer_read_enum (ib, LTO_symtab_tags, LTO_symtab_last_tag); > - } > - > - lto_destroy_simple_input_block (file_data, LTO_section_offload_table, > + lto_destroy_simple_input_block (file_data, LTO_section_offload_data, > ib, data, len); > } > + > + /* Take action if the target has the function_glibc_finite_math property > set, > + and that doesn't match the current (that is, offloading target's). */ > + bool g_f_m = targetm.libc_has_function (function_glibc_finite_math); > + if (g_f_m_target && !g_f_m) > + { > + struct cgraph_node *node; > + FOR_EACH_FUNCTION (node) > + { > + /* This only applies to references to external math functions. */ > + if (!DECL_EXTERNAL (node->decl)) > + continue; > + /* All the relevant math functions are registered as GCC builtins. */ > + if (!DECL_BUILT_IN (node->decl) > + || (mathfn_built_in (TREE_TYPE (TREE_TYPE (node->decl)), > + DECL_FUNCTION_CODE (node->decl)) > + == NULL_TREE)) > + continue; > + /* Check whether the assembler name for "[function]" has been set to > + "__[function]_finite". */ > + if (!DECL_ASSEMBLER_NAME_SET_P (node->decl)) > + continue; > + const char *asm_name > + = IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (node->decl)); > + if (*asm_name++ != '*') > + continue; > + size_t ulp_len = strlen (user_label_prefix); > + if (ulp_len == 0) > + ; > + else if (strncmp (asm_name, user_label_prefix, ulp_len) == 0) > + asm_name += ulp_len; > + else > + continue; > + if (*asm_name++ != '_') > + continue; > + if (*asm_name++ != '_') > + continue; > + const char *name = IDENTIFIER_POINTER (DECL_NAME (node->decl)); > + size_t name_len = strlen (name); > + if (strncmp (asm_name, name, name_len) == 0) > + asm_name += name_len; > + else > + continue; > + if (strcmp (asm_name, "_finite") != 0) > + continue; > + /* ..., and if yes, reset it. */ > + symtab->change_decl_assembler_name (node->decl, > + DECL_NAME (node->decl)); > + } > + } > +} > + > +/* Input function/variable tables that will allow libgomp to look up offload > + target code, and store them into OFFLOAD_FUNCS and OFFLOAD_VARS. */ > + > +static void > +input_offload_tables (struct lto_input_block *ib, > + struct lto_file_decl_data *file_data, > + bool do_force_output) > +{ > + enum LTO_symtab_tags tag > + = streamer_read_enum (ib, LTO_symtab_tags, LTO_symtab_last_tag); > + while (tag) > + { > + if (tag == LTO_symtab_unavail_node) > + { > + int decl_index = streamer_read_uhwi (ib); > + tree fn_decl > + = lto_file_decl_data_get_fn_decl (file_data, decl_index); > + vec_safe_push (offload_funcs, fn_decl); > + > + /* Prevent IPA from removing fn_decl as unreachable, since there > + may be no refs from the parent function to child_fn in offload > + LTO mode. */ > + if (do_force_output) > + cgraph_node::get (fn_decl)->mark_force_output (); > + } > + else if (tag == LTO_symtab_variable) > + { > + int decl_index = streamer_read_uhwi (ib); > + tree var_decl > + = lto_file_decl_data_get_var_decl (file_data, decl_index); > + vec_safe_push (offload_vars, var_decl); > + > + /* Prevent IPA from removing var_decl as unused, since there > + may be no refs to var_decl in offload LTO mode. */ > + if (do_force_output) > + varpool_node::get (var_decl)->force_output = 1; > + } > + else > + fatal_error (input_location, > + "invalid offload table in %s", file_data->file_name); > + > + tag = streamer_read_enum (ib, LTO_symtab_tags, LTO_symtab_last_tag); > + } > } > > /* True when we need optimization summary for NODE. */ > diff --git gcc/lto-streamer-out.c gcc/lto-streamer-out.c > index 35e58fd..616266b 100644 > --- gcc/lto-streamer-out.c > +++ gcc/lto-streamer-out.c > @@ -2385,7 +2385,7 @@ lto_output (void) > statements using the statement UIDs. */ > output_symtab (); > > - output_offload_tables (); > + output_offload_data (); > > #if CHECKING_P > lto_bitmap_free (output); > diff --git gcc/lto-streamer.h gcc/lto-streamer.h > index 92efdb8..df42cbd 100644 > --- gcc/lto-streamer.h > +++ gcc/lto-streamer.h > @@ -242,7 +242,7 @@ enum lto_section_type > LTO_section_inline_summary, > LTO_section_ipcp_transform, > LTO_section_ipa_icf, > - LTO_section_offload_table, > + LTO_section_offload_data, > LTO_section_mode_table, > LTO_section_ipa_hsa, > LTO_N_SECTION_TYPES /* Must be last. */ > @@ -914,8 +914,8 @@ bool lto_symtab_encoder_encode_initializer_p > (lto_symtab_encoder_t, > varpool_node *); > void output_symtab (void); > void input_symtab (void); > -void output_offload_tables (void); > -void input_offload_tables (bool); > +void output_offload_data (void); > +void input_offload_data (bool); > bool referenced_from_other_partition_p (struct ipa_ref_list *, > lto_symtab_encoder_t); > bool reachable_from_other_partition_p (struct cgraph_node *, > diff --git gcc/lto/lto.c gcc/lto/lto.c > index af735cb..c46bfa7 100644 > --- gcc/lto/lto.c > +++ gcc/lto/lto.c > @@ -2855,7 +2855,7 @@ read_cgraph_and_symbols (unsigned nfiles, const char > **fnames) > /* Read the symtab. */ > input_symtab (); > > - input_offload_tables (!flag_ltrans); > + input_offload_data (!flag_ltrans); > > /* Store resolutions into the symbol table. */ > > diff --git gcc/target.def gcc/target.def > index 6392e73..2ce827d 100644 > --- gcc/target.def > +++ gcc/target.def > @@ -2533,7 +2533,7 @@ set via @code{__attribute__}.", > > DEFHOOK > (libc_has_function, > - "This hook determines whether a function from a class of functions\n\ > + "This hook determines properties, such as whether a class of functions\n\ > @var{fn_class} is present at the runtime.", > bool, (enum function_class fn_class), > default_libc_has_function) > diff --git gcc/targhooks.c gcc/targhooks.c > index 6b4601b..c1f3c15 100644 > --- gcc/targhooks.c > +++ gcc/targhooks.c > @@ -1389,7 +1389,7 @@ default_have_conditional_execution (void) > } > > /* By default we assume that c99 functions are present at the runtime, > - but sincos is not. */ > + but others are not. */ > bool > default_libc_has_function (enum function_class fn_class) > { Grüße Thomas
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