Hi,
PR lto/80838 is about lto+profiledbootstrapped compiler being slower than
profiledboostrapped compiler.
This is caused by a fact that some of object files linked into cc1plus binary
are built with -fPIC and lto-wrapper then decides to make whole binary PIC that
is very slow. While we probably ought to avoid linking PIC code into static
binary but I saw similar issue with firefox and other programs.
I do not think we want to support mixed PIC/non-PIC symbols internally, because
it would need quite some work and I do not see any reasonable use cases.
This patch makes merging more realistic/agressive. Linking -fPIC and non-PIC
code together results in non-PIC binary and thus the corresponding flags are
dropped when mismatches occurs.
It would be nice to warn about it, but I do not know how to make warning
meaningful on targets that are PIC by default.
Bootstrapped/regtested x86_64-linux, plan to commit it tomorrow after
lto-boottrapping if there are no complains.
Honza
PR lto/80838
* lto-wrapper.c (remove_option): New function.
(merge_and_complain): Merge PIC/PIE options more realistically.
Index: lto-wrapper.c
===================================================================
--- lto-wrapper.c (revision 250054)
+++ lto-wrapper.c (working copy)
@@ -192,6 +192,20 @@ append_option (struct cl_decoded_option
sizeof (struct cl_decoded_option));
}
+/* Remove option number INDEX from DECODED_OPTIONS, update
+ DECODED_OPTIONS_COUNT. */
+
+static void
+remove_option (struct cl_decoded_option **decoded_options,
+ int index, unsigned int *decoded_options_count)
+{
+ --*decoded_options_count;
+ memmove (&(*decoded_options)[index + 1],
+ &(*decoded_options)[index],
+ sizeof (struct cl_decoded_option)
+ * (*decoded_options_count - index));
+}
+
/* Try to merge and complain about options FDECODED_OPTIONS when applied
ontop of DECODED_OPTIONS. */
@@ -202,6 +216,8 @@ merge_and_complain (struct cl_decoded_op
unsigned int fdecoded_options_count)
{
unsigned int i, j;
+ struct cl_decoded_option *pic_option = NULL;
+ struct cl_decoded_option *pie_option = NULL;
/* ??? Merge options from files. Most cases can be
handled by either unioning or intersecting
@@ -238,10 +254,6 @@ merge_and_complain (struct cl_decoded_op
case OPT_fdiagnostics_show_option:
case OPT_fdiagnostics_show_location_:
case OPT_fshow_column:
- case OPT_fPIC:
- case OPT_fpic:
- case OPT_fPIE:
- case OPT_fpie:
case OPT_fcommon:
case OPT_fgnu_tm:
/* Do what the old LTO code did - collect exactly one option
@@ -255,6 +267,16 @@ merge_and_complain (struct cl_decoded_op
append_option (decoded_options, decoded_options_count, foption);
break;
+ /* Figure out what PIC/PIE level wins and merge the results. */
+ case OPT_fPIC:
+ case OPT_fpic:
+ pic_option = foption;
+ break;
+ case OPT_fPIE:
+ case OPT_fpie:
+ pie_option = foption;
+ break;
+
case OPT_fopenmp:
case OPT_fopenacc:
case OPT_fcilkplus:
@@ -286,18 +308,6 @@ merge_and_complain (struct cl_decoded_op
foption->orig_option_with_args_text);
break;
- case OPT_foffload_abi_:
- for (j = 0; j < *decoded_options_count; ++j)
- if ((*decoded_options)[j].opt_index == foption->opt_index)
- break;
- if (j == *decoded_options_count)
- append_option (decoded_options, decoded_options_count, foption);
- else if (foption->value != (*decoded_options)[j].value)
- fatal_error (input_location,
- "Option %s not used consistently in all LTO input"
- " files", foption->orig_option_with_args_text);
- break;
-
case OPT_O:
case OPT_Ofast:
case OPT_Og:
@@ -368,12 +378,70 @@ merge_and_complain (struct cl_decoded_op
(*decoded_options)[j].value = 1;
}
break;
+
+
+ case OPT_foffload_abi_:
+ for (j = 0; j < *decoded_options_count; ++j)
+ if ((*decoded_options)[j].opt_index == foption->opt_index)
+ break;
+ if (j == *decoded_options_count)
+ append_option (decoded_options, decoded_options_count, foption);
+ else if (foption->value != (*decoded_options)[j].value)
+ fatal_error (input_location,
+ "Option %s not used consistently in all LTO input"
+ " files", foption->orig_option_with_args_text);
+ break;
+
case OPT_foffload_:
append_option (decoded_options, decoded_options_count, foption);
break;
}
}
+
+ /* Merge PIC options:
+ -fPIC + -fpic = -fpic
+ -fPIC + -fno-pic = -fno-pic
+ -fpic/-fPIC + nothin = nothing.
+ It is a common mistake to mix few -fPIC compiled objects into otherwise
+ non-PIC code. We do not want to build everything with PIC then.
+
+ It would be good to warn on mismatches, but it is bit hard to do as
+ we do not know what nothing translates to. */
+
+ for (unsigned int j = 0; j < *decoded_options_count;)
+ if ((*decoded_options)[j].opt_index == OPT_fPIC
+ || (*decoded_options)[j].opt_index == OPT_fpic)
+ {
+ if (!pic_option
+ || (pic_option->value > 0) != ((*decoded_options)[j].value > 0))
+ remove_option (decoded_options, j, decoded_options_count);
+ else if (pic_option->opt_index == OPT_fPIC
+ && (*decoded_options)[j].opt_index == OPT_fpic)
+ {
+ (*decoded_options)[j] = *pic_option;
+ j++;
+ }
+ else
+ j++;
+ }
+ else if ((*decoded_options)[j].opt_index == OPT_fPIE
+ || (*decoded_options)[j].opt_index == OPT_fpie)
+ {
+ if (!pie_option
+ || pie_option->value != (*decoded_options)[j].value)
+ remove_option (decoded_options, j, decoded_options_count);
+ else if (pie_option->opt_index == OPT_fPIE
+ && (*decoded_options)[j].opt_index == OPT_fpie)
+ {
+ (*decoded_options)[j] = *pie_option;
+ j++;
+ }
+ else
+ j++;
+ }
+ else
+ j++;
}
/* Auxiliary function that frees elements of PTR and PTR itself.
