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From 0de967c51189535f8d00943ccc91a3ad07e50ef2 Mon Sep 17 00:00:00 2001
From: wangchunyang <wangchunyang15@huawei.com>
Date: Wed, 11 Sep 2024 17:27:19 +0800
Subject: [PATCH 4/5] add flag -flto-try enable LTO and automatically skip in
inapplicable situation.
---
gcc/collect2.cc | 51 ++++++++++++++++++++++++++++++++++++++++++-
gcc/common.opt | 8 +++++++
gcc/opts-common.cc | 54 +++++++++++++++++++++++++++++++++++++++++++++-
gcc/opts.cc | 20 +++++++++++++++++
4 files changed, 131 insertions(+), 2 deletions(-)
diff --git a/gcc/collect2.cc b/gcc/collect2.cc
index 9715e8eee..690363880 100644
--- a/gcc/collect2.cc
+++ b/gcc/collect2.cc
@@ -200,6 +200,7 @@ static enum lto_mode_d lto_mode = LTO_MODE_WHOPR;
#else
static enum lto_mode_d lto_mode = LTO_MODE_NONE;
#endif
+static bool maybe_relink_without_lto = false;
bool helpflag; /* true if --help */
@@ -751,7 +752,53 @@ do_link (char **ld_argv, const char *atsuffix)
PEX_LAST | PEX_SEARCH,
HAVE_GNU_LD && at_file_supplied, atsuffix);
int ret = collect_wait (prog, pex);
- if (ret)
+ if (ret && maybe_relink_without_lto)
+ {
+ bool link_with_lto_plugin_before = false;
+ for (int i = 0, j = -1; ld_argv[i]; ++i)
+ {
+ if (endswith (ld_argv[i], "liblto_plugin.so"))
+ {
+ link_with_lto_plugin_before = true;
+ for (j = i + 1; ld_argv[j]; ++j)
+ {
+ if (!startswith (ld_argv[j], "-plugin-opt="))
+ break;
+ }
+ for (i = i - 1; ; ++i, ++j)
+ {
+ ld_argv[i] = ld_argv[j];
+ if (ld_argv[j] == NULL)
+ break;
+ }
+ break;
+ }
+ }
+ int ret2 = 0;
+ if (link_with_lto_plugin_before)
+ {
+ fprintf (stderr, "lto link fail, relinking without lto");
+ lto_mode = LTO_MODE_NONE;
+ pex = collect_execute (prog, ld_argv, NULL, NULL,
+ PEX_LAST | PEX_SEARCH,
+ HAVE_GNU_LD && at_file_supplied, atsuffix);
+ ret2 = collect_wait (prog, pex);
+ }
+ else
+ ret2 = ret;
+ if (ret2)
+ {
+ error ("ld returned %d exit status", ret);
+ exit (ret);
+ }
+ else
+ {
+ /* We have just successfully produced an output file, so assume that
+ we may unlink it if need be for now on. */
+ may_unlink_output_file = true;
+ }
+ }
+ else if (ret)
{
error ("ld returned %d exit status", ret);
exit (ret);
@@ -1009,6 +1056,8 @@ main (int argc, char **argv)
num_c_args++;
if (startswith (q, "-flto-partition=none"))
no_partition = true;
+ else if (startswith (q, "-flto-try"))
+ maybe_relink_without_lto = true;
else if (startswith (q, "-fno-lto"))
lto_mode = LTO_MODE_NONE;
else if (startswith (q, "-save-temps"))
diff --git a/gcc/common.opt b/gcc/common.opt
index 96888cf1b..0895c6114 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -70,6 +70,10 @@ bool flag_warn_unused_result = false
Variable
int flag_generate_lto
+; Nonzero if we should write GIMPLE bytecode for link-time optimization.
+Variable
+int flag_relink_whthout_lto = 0
+
; Nonzero if we should write GIMPLE bytecode for offload compilation.
Variable
int flag_generate_offload = 0
@@ -2161,6 +2165,10 @@ flto
Common
Enable link-time optimization.
+flto-try
+Common Var(flag_lto_try) Init(0)
+Do link-time optimization as much as possible.
+
flto=
Common RejectNegative Joined Var(flag_lto)
Link-time optimization with number of parallel jobs or jobserver.
diff --git a/gcc/opts-common.cc b/gcc/opts-common.cc
index 33c696f3d..176041bfe 100644
--- a/gcc/opts-common.cc
+++ b/gcc/opts-common.cc
@@ -1162,7 +1162,50 @@ decode_cmdline_options_to_array (unsigned int argc, const char **argv,
struct cl_decoded_option *opt_array;
unsigned int num_decoded_options;
- int opt_array_len = argc;
+ enum LTO_SKIP_STAT
+ {
+ NO_NEED_TO_SKIP,
+ NEED_TO_SKIP,
+ ALREADY_SKIP,
+ };
+ LTO_SKIP_STAT lto_skip_stat = NO_NEED_TO_SKIP;
+ bool try_use_lto = false;
+ const char* lto_option_conflict = NULL;
+ const char* wrap_option = "-Wl,--wrap=";
+ const char* start_lib_option = "-Wl,--start-lib";
+ for (i = 1; i < argc; i += 1)
+ {
+ if (startswith (argv[i], "-flto-try"))
+ {
+ try_use_lto = true;
+ }
+
+ if (startswith (argv[i], wrap_option)
+ && (lto_skip_stat == NO_NEED_TO_SKIP))
+ {
+ lto_option_conflict = wrap_option;
+ lto_skip_stat = NEED_TO_SKIP;
+ }
+ else if (startswith (argv[i], start_lib_option)
+ && (lto_skip_stat == NO_NEED_TO_SKIP))
+ {
+ lto_option_conflict = start_lib_option;
+ lto_skip_stat = NEED_TO_SKIP;
+ }
+ else if (startswith (argv[i], "-fno-lto"))
+ {
+ lto_option_conflict = NULL;
+ lto_skip_stat = ALREADY_SKIP;
+ break;
+ }
+ }
+ if (!try_use_lto)
+ {
+ lto_skip_stat = NO_NEED_TO_SKIP;
+ lto_option_conflict = NULL;
+ }
+
+ int opt_array_len = lto_skip_stat == NEED_TO_SKIP ? argc + 1 : argc;
opt_array = XNEWVEC (struct cl_decoded_option, opt_array_len);
opt_array[0].opt_index = OPT_SPECIAL_program_name;
@@ -1244,6 +1287,15 @@ decode_cmdline_options_to_array (unsigned int argc, const char **argv,
num_decoded_options += handle_machine_option (lang_mask, num_decoded_options,
argc, argv, opt_array);
+ if (lto_skip_stat == NEED_TO_SKIP)
+ {
+ const char * nolto = "-fno-lto";
+ fprintf (stderr, "skip lto for %s\n", lto_option_conflict);
+ decode_cmdline_option (&nolto, lang_mask,
+ &opt_array[num_decoded_options]);
+ num_decoded_options++;
+ }
+
*decoded_options = opt_array;
*decoded_options_count = num_decoded_options;
prune_options (decoded_options, decoded_options_count, lang_mask);
diff --git a/gcc/opts.cc b/gcc/opts.cc
index 84dd8925a..9ccc22510 100644
--- a/gcc/opts.cc
+++ b/gcc/opts.cc
@@ -1143,6 +1143,26 @@ finish_options (struct gcc_options *opts, struct gcc_options *opts_set,
SET_OPTION_IF_UNSET (opts, opts_set, param_stack_frame_growth, 40);
}
+ if (opts->x_flag_lto_try)
+ {
+#ifdef ENABLE_LTO
+ if (opts_set->x_flag_lto && opts->x_flag_lto)
+ {
+ inform (loc, "%<-flto-try%> don't guarantee that lto "
+ "will be enabled.");
+ }
+ opts->x_flag_lto = "";
+ if (opts_set->x_flag_fat_lto_objects && !opts->x_flag_fat_lto_objects)
+ {
+ error_at (loc, "%<-flto-try%> are not supported with "
+ "-fno-fat-lto-objects");
+ }
+ opts->x_flag_fat_lto_objects = 1;
+#else
+ error_at (loc, "LTO support has not been enabled in this configuration");
+#endif
+ }
+
if (opts->x_flag_lto)
{
#ifdef ENABLE_LTO
--
2.33.0
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