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| author | Jan Hubicka <jh@suse.cz> | 2022-12-21 12:41:25 +0100 |
|---|---|---|
| committer | Jan Hubicka <jh@suse.cz> | 2022-12-21 12:41:25 +0100 |
| commit | 39ebd3a9f5cb8555bcb0422086e646ce833028a4 (patch) | |
| tree | 18b06befdc9a62afaaddc00c2daefc21c71a58d3 | |
| parent | 88709c4a1e6f8b69a33897a1ab46b8d66c4569c4 (diff) | |
| download | gcc-39ebd3a9f5cb8555bcb0422086e646ce833028a4.zip gcc-39ebd3a9f5cb8555bcb0422086e646ce833028a4.tar.gz gcc-39ebd3a9f5cb8555bcb0422086e646ce833028a4.tar.bz2 | |
Make -fwhole-program to work with incremental LTO linking
Update documentation of -fwhole-program which was wrongly
claiming that it is useless with LTO whole it is useful for LTO without plugin
and extends -fwhole-program to also work with incremental linking.
This is useful when building kernel where the incremental link is de-facto fina
binary and only some explicitly marked symbols needs to remain.
Bootstrapped/regtested x86_64-linux, comitted.
gcc/ChangeLog:
2022-12-21 Jan Hubicka <hubicka@ucw.cz>
* doc/invoke.texi: Fix documentation of -fwhole-program with LTO
and document behaviour for incremental linking.
gcc/lto/ChangeLog:
2022-12-21 Jan Hubicka <hubicka@ucw.cz>
* lto-common.cc (lto_resolution_read): With incremental linking
and whole program ignore turn LDPR_PREVAILING_DEF_IRONLY to
LDPR_PREVAILING_DEF_IRONLY_EXP
* lto-lang.cc (lto_post_options): Do not clear flag_whole_program
for incremental link
| -rw-r--r-- | gcc/doc/invoke.texi | 9 | ||||
| -rw-r--r-- | gcc/lto/lto-common.cc | 11 | ||||
| -rw-r--r-- | gcc/lto/lto-lang.cc | 1 |
3 files changed, 17 insertions, 4 deletions
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index d8a2079..da9ad10 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -13719,9 +13719,12 @@ compiled. All public functions and variables with the exception of @code{main} and those merged by attribute @code{externally_visible} become static functions and in effect are optimized more aggressively by interprocedural optimizers. -This option should not be used in combination with @option{-flto}. -Instead relying on a linker plugin should provide safer and more precise -information. +With @option{-flto} this option has a limited use. In most cases the +precise list of symbols used or exported from the binary is known the +resolution info passed to the link-time optimizer by the linker plugin. It is +still useful if no linker plugin is used or during incremental link step when +final code is produced (with @option{-flto} +@option{-flinker-output=nolto-rel}). @item -flto[=@var{n}] @opindex flto diff --git a/gcc/lto/lto-common.cc b/gcc/lto/lto-common.cc index f643097..125064b 100644 --- a/gcc/lto/lto-common.cc +++ b/gcc/lto/lto-common.cc @@ -2118,6 +2118,17 @@ lto_resolution_read (splay_tree file_ids, FILE *resolution, lto_file *file) if (strcmp (lto_resolution_str[j], r_str) == 0) { r = (enum ld_plugin_symbol_resolution) j; + /* Incremental linking together with -fwhole-program may seem + somewhat contradictionary (as the point of incremental linking + is to allow re-linking with more symbols later) but it is + used to build LTO kernel. We want to hide all symbols that + are not explicitely marked as exported and thus turn + LDPR_PREVAILING_DEF_IRONLY_EXP + to LDPR_PREVAILING_DEF_IRONLY. */ + if (flag_whole_program + && flag_incremental_link == INCREMENTAL_LINK_NOLTO + && r == LDPR_PREVAILING_DEF_IRONLY_EXP) + r = LDPR_PREVAILING_DEF_IRONLY; break; } } diff --git a/gcc/lto/lto-lang.cc b/gcc/lto/lto-lang.cc index d36453b..7018dfa 100644 --- a/gcc/lto/lto-lang.cc +++ b/gcc/lto/lto-lang.cc @@ -901,7 +901,6 @@ lto_post_options (const char **pfilename ATTRIBUTE_UNUSED) break; case LTO_LINKER_OUTPUT_NOLTOREL: /* .o: incremental link producing asm */ - flag_whole_program = 0; flag_incremental_link = INCREMENTAL_LINK_NOLTO; break; |