Re: [PATCH] Try LTO partial linking. (Was: Speed of compiling gimple-match.c)

[Martin Liška]

On 5/20/21 5:55 PM, Jan Hubicka wrote:

Quick solution is to also modify partitioner to use the local symbol
names when doing incremental linking (those mixing in source code and
random seeds) to avoid clashes.

Good hint. I added hash based on object file name (I don't want to handle
proper string escaping) and -frandom-seed.

What do you think about the patch?
Thanks,
Martin

>From 372d2944571906932fd1419bfc51a949d67b857e Mon Sep 17 00:00:00 2001
From: Martin Liska <mli...@suse.cz>
Date: Fri, 21 May 2021 10:25:49 +0200
Subject: [PATCH] LTO: add lto_priv suffixfor LTO_LINKER_OUTPUT_NOLTOREL.

gcc/lto/ChangeLog:

	* lto-partition.c (privatize_symbol_name_1): Add random suffix
	based on hash of the object file and -frandom-seed.
---
 gcc/lto/lto-partition.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/gcc/lto/lto-partition.c b/gcc/lto/lto-partition.c
index 15761ac9eb5..fef48c869a2 100644
--- a/gcc/lto/lto-partition.c
+++ b/gcc/lto/lto-partition.c
@@ -35,6 +35,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "ipa-fnsummary.h"
 #include "lto-partition.h"
 #include "sreal.h"
+#include "toplev.h"
 
 vec<ltrans_partition> ltrans_partitions;
 
@@ -941,9 +942,23 @@ privatize_symbol_name_1 (symtab_node *node, tree decl)
 
   name = maybe_rewrite_identifier (name);
   unsigned &clone_number = lto_clone_numbers->get_or_insert (name);
-  symtab->change_decl_assembler_name (decl,
-				      clone_function_name (
-					  name, "lto_priv", clone_number));
+
+  char *suffix = NULL;
+  if (flag_lto_linker_output == LTO_LINKER_OUTPUT_NOLTOREL)
+    {
+      hashval_t fnhash = 0;
+      if (node->lto_file_data != NULL)
+	fnhash = htab_hash_string (node->lto_file_data->file_name);
+      suffix = XNEWVEC (char, 128);
+      char sep = symbol_table::symbol_suffix_separator ();
+      sprintf (suffix, "lto_priv%c%u%c%" PRIu64, sep, fnhash, sep,
+	       (unsigned HOST_WIDE_INT)get_random_seed (false));
+    }
+
+  tree clone
+    = clone_function_name (name, suffix ? suffix : "lto_priv", clone_number);
+  symtab->change_decl_assembler_name (decl, clone);
+  free (suffix);
   clone_number++;
 
   if (node->lto_file_data)
-- 
2.31.1