Hi, with lto, incremental linking can be meaninfuly done in three ways: 1) read LTO file and produce non-LTO .o file this is current behaviour of gcc -r or ld -r with plugin 2) read LTO files and merge section for later LTO this is current behaviour of ld -r w/o plugin 3) read LTO files into the compiler, link them and produce incrementaly linked LTO object.
3 makes most sense and I am maing it new default for gcc -r. For testing purposes and perhaps in order to have tool to turn LTO object into real object, we want to have 1) available as well. GCC currently have -flinker-output option that decides between modes that is decided by linker plugin and can be overwritten by user (I have forgot to document this). I am targeting for -flinker-output=rel to be incremental linking into LTO and adding -flinker-output=nolto-rel for 1). The main limitation of 2 and 3 is that you can not link LTO and non-LTO object files theger. For 2 HJ's binutils patchset has support and I think it can be extended to handle 3 as well. But with default binutils we want to warn users. This patch implements the warning (and prevents linker plugin to add redundat linker-ouptut options. Bootstrapped/regtested x86_64-linux with rest of the inclink patchset. OK? * lto-plugin.c: (non_claimed_files): New static var. (linker_ouput_known): New static var. (all_symbols_read_handler): When user specifies linker output do not imply it; output warning when nonlto-rel mode is forced. (claim_file_header): Record number of nonclaimed files. (process_option): Remember if linker output is known Index: lto-plugin.c =================================================================== --- lto-plugin.c (revision 260042) +++ lto-plugin.c (working copy) @@ -27,10 +27,13 @@ More information at http://gcc.gnu.org/wiki/whopr/driver. This plugin should be passed the lto-wrapper options and will forward them. - It also has 2 options of its own: + It also has options at his own: -debug: Print the command line used to run lto-wrapper. -nop: Instead of running lto-wrapper, pass the original to the plugin. This - only works if the input files are hybrid. */ + only works if the input files are hybrid. + -linker-output-known: Do not determine linker output + -sym-style={none,win32,underscore|uscore} + -pass-through */ #ifdef HAVE_CONFIG_H #include "config.h" @@ -159,6 +162,7 @@ static struct plugin_file_info *claimed_files = NULL; static unsigned int num_claimed_files = 0; +static unsigned int non_claimed_files = 0; /* List of files with offloading. */ static struct plugin_offload_file *offload_files; @@ -185,6 +189,7 @@ static char *resolution_file = NULL; static enum ld_plugin_output_file_type linker_output; static int linker_output_set; +static int linker_output_known; /* The version of gold being used, or -1 if not gold. The number is MAJOR * 100 + MINOR. */ @@ -637,7 +642,8 @@ all_symbols_read_handler (void) { unsigned i; - unsigned num_lto_args = num_claimed_files + lto_wrapper_num_args + 3; + unsigned num_lto_args = num_claimed_files + lto_wrapper_num_args + 2 + + !linker_output_known; char **lto_argv; const char *linker_output_str = NULL; const char **lto_arg_ptr; @@ -661,26 +667,37 @@ for (i = 0; i < lto_wrapper_num_args; i++) *lto_arg_ptr++ = lto_wrapper_argv[i]; - assert (linker_output_set); - switch (linker_output) + if (!linker_output_known) { - case LDPO_REL: - linker_output_str = "-flinker-output=rel"; - break; - case LDPO_DYN: - linker_output_str = "-flinker-output=dyn"; - break; - case LDPO_PIE: - linker_output_str = "-flinker-output=pie"; - break; - case LDPO_EXEC: - linker_output_str = "-flinker-output=exec"; - break; - default: - message (LDPL_FATAL, "unsupported linker output %i", linker_output); - break; + assert (linker_output_set); + switch (linker_output) + { + case LDPO_REL: + if (non_claimed_files) + { + message (LDPL_WARNING, "incremental linking of LTO and non-LTO " + "objects; using -flinker-output=nolto-rel which will " + "bypass whole program optimization"); + linker_output_str = "-flinker-output=nolto-rel"; + } + else + linker_output_str = "-flinker-output=rel"; + break; + case LDPO_DYN: + linker_output_str = "-flinker-output=dyn"; + break; + case LDPO_PIE: + linker_output_str = "-flinker-output=pie"; + break; + case LDPO_EXEC: + linker_output_str = "-flinker-output=exec"; + break; + default: + message (LDPL_FATAL, "unsupported linker output %i", linker_output); + break; + } + *lto_arg_ptr++ = xstrdup (linker_output_str); } - *lto_arg_ptr++ = xstrdup (linker_output_str); if (num_offload_files > 0) { @@ -1108,6 +1125,7 @@ goto cleanup; err: + non_claimed_files++; free (lto_file.name); cleanup: @@ -1122,6 +1140,8 @@ static void process_option (const char *option) { + if (strcmp (option, "-linker-output-known") == 0) + linker_output_known = 1; if (strcmp (option, "-debug") == 0) debug = 1; else if (strcmp (option, "-nop") == 0)