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[PATCH 1/2] Change random seeds to 64bit and drop re-crcing
- From: Andi Kleen <andi at firstfloor dot org>
- To: gcc-patches at gcc dot gnu dot org
- Cc: hubicka at ucw dot cz, Andi Kleen <ak at linux dot intel dot com>
- Date: Tue, 27 Sep 2011 23:30:15 +0200
- Subject: [PATCH 1/2] Change random seeds to 64bit and drop re-crcing
From: Andi Kleen <ak@linux.intel.com>
I had some trouble with random build failures in a large LTO project
and it turned out to be random seed collisions in a highly parallel build
(thanks to Honza for suggesting that)
There were multiple problems:
- The way to generate the random seed is pure (milli seconds plus pid)
- It's only 32bit
- Several users take the existing ascii seed and re-CRC32 it again, which
doesn't exactly improve it.
This patch changes that to:
- Always use 64bit seeds as numbers (no re-crcing)
- Change all users to use HOST_WIDE_INT
- When the user specifies a random seed it's still crc32ed, but only in
this case.
Passes bootstrap + testsuite on x86_64-linux. Ok to commit?
-Andi
gcc/cp:
2011-09-26 Andi Kleen <ak@linux.intel.com>
* repo.c (finish_repo): Use HOST_WIDE_INT_PRINT_HEX_PURE.
gcc/:
2011-09-26 Andi Kleen <ak@linux.intel.com>
* hwint.h (HOST_WIDE_INT_PRINT_HEX_PURE): Add.
* lto-streamer.c (lto_get_section_name): Remove crc32_string.
Handle numerical random seed.
* lto-streamer.h (lto_file_decl_data): Change id to unsigned HOST_WIDE_INT.
* toplev.c (random_seed): Add.
(init_random_seed): Change for numerical random seed.
(get_random_seed): Return as HOST_WIDE_INT.
(set_random_seed): Crc32 existing string.
* toplev.h (get_random_seed): Change to numercal return.
* tree.c (get_file_function_name): Remove CRC. Handle numerical random seed.
gcc/lto/:
2011-09-26 Andi Kleen <ak@linux.intel.com>
* lto.c (lto_resolution_read): Remove id dumping.
(lto_section_with_id): Turn id HOST_WIDE_ID.
(create_subid_section_table): Dito.
---
gcc/cp/repo.c | 3 ++-
gcc/hwint.h | 1 +
gcc/lto-streamer.c | 8 ++++----
gcc/lto-streamer.h | 2 +-
gcc/lto/lto.c | 11 ++++-------
gcc/toplev.c | 23 ++++++++++++-----------
gcc/toplev.h | 2 +-
gcc/tree.c | 6 +++---
8 files changed, 28 insertions(+), 28 deletions(-)
diff --git a/gcc/cp/repo.c b/gcc/cp/repo.c
index 16a192e..ca971b6 100644
--- a/gcc/cp/repo.c
+++ b/gcc/cp/repo.c
@@ -263,7 +263,8 @@ finish_repo (void)
anonymous namespaces will get the same mangling when this
file is recompiled. */
if (!strstr (args, "'-frandom-seed="))
- fprintf (repo_file, " '-frandom-seed=%s'", get_random_seed (false));
+ fprintf (repo_file, " '-frandom-seed=" HOST_WIDE_INT_PRINT_HEX_PURE "'",
+ get_random_seed (false));
fprintf (repo_file, "\n");
}
diff --git a/gcc/hwint.h b/gcc/hwint.h
index 2643aee..f5e0bee 100644
--- a/gcc/hwint.h
+++ b/gcc/hwint.h
@@ -102,6 +102,7 @@ extern char sizeof_long_long_must_be_8[sizeof(long long) == 8 ? 1 : -1];
#define HOST_WIDE_INT_PRINT_DEC_C HOST_WIDE_INT_PRINT_DEC HOST_WIDE_INT_PRINT_C
#define HOST_WIDE_INT_PRINT_UNSIGNED "%" HOST_WIDE_INT_PRINT "u"
#define HOST_WIDE_INT_PRINT_HEX "%#" HOST_WIDE_INT_PRINT "x"
+#define HOST_WIDE_INT_PRINT_HEX_PURE "%" HOST_WIDE_INT_PRINT "x"
/* Set HOST_WIDEST_INT. This is a 64-bit type unless the compiler
in use has no 64-bit type at all; in that case it's 32 bits. */
diff --git a/gcc/lto-streamer.c b/gcc/lto-streamer.c
index 633c3ce..e3ccb79 100644
--- a/gcc/lto-streamer.c
+++ b/gcc/lto-streamer.c
@@ -166,13 +166,13 @@ lto_get_section_name (int section_type, const char *name, struct lto_file_decl_d
doesn't confuse the reader with merged sections.
For options don't add a ID, the option reader cannot deal with them
- and merging should be ok here.
-
- XXX: use crc64 to minimize collisions? */
+ and merging should be ok here. */
if (section_type == LTO_section_opts)
strcpy (post, "");
+ else if (f != NULL)
+ sprintf (post, "." HOST_WIDE_INT_PRINT_HEX_PURE, f->id);
else
- sprintf (post, ".%x", f ? f->id : crc32_string(0, get_random_seed (false)));
+ sprintf (post, "." HOST_WIDE_INT_PRINT_HEX_PURE, get_random_seed (false));
return concat (LTO_SECTION_NAME_PREFIX, sep, add, post, NULL);
}
diff --git a/gcc/lto-streamer.h b/gcc/lto-streamer.h
index 190d6a3..2564bd2 100644
--- a/gcc/lto-streamer.h
+++ b/gcc/lto-streamer.h
@@ -552,7 +552,7 @@ struct GTY(()) lto_file_decl_data
struct lto_file_decl_data *next;
/* Sub ID for merged objects. */
- unsigned id;
+ unsigned HOST_WIDE_INT id;
/* Symbol resolutions for this file */
VEC(ld_plugin_symbol_resolution_t,heap) * GTY((skip)) resolutions;
diff --git a/gcc/lto/lto.c b/gcc/lto/lto.c
index 0b1dcb9..77eb1a1 100644
--- a/gcc/lto/lto.c
+++ b/gcc/lto/lto.c
@@ -976,9 +976,6 @@ lto_resolution_read (splay_tree file_ids, FILE *resolution, lto_file *file)
}
file_data = (struct lto_file_decl_data *)nd->value;
- if (cgraph_dump_file)
- fprintf (cgraph_dump_file, "Adding resolution %u %u to id %x\n",
- index, r, file_data->id);
VEC_safe_grow_cleared (ld_plugin_symbol_resolution_t, heap,
file_data->resolutions,
max_index + 1);
@@ -990,14 +987,14 @@ lto_resolution_read (splay_tree file_ids, FILE *resolution, lto_file *file)
/* Is the name for a id'ed LTO section? */
static int
-lto_section_with_id (const char *name, unsigned *id)
+lto_section_with_id (const char *name, unsigned HOST_WIDE_INT *id)
{
const char *s;
if (strncmp (name, LTO_SECTION_NAME_PREFIX, strlen (LTO_SECTION_NAME_PREFIX)))
return 0;
s = strrchr (name, '.');
- return s && sscanf (s, ".%x", id) == 1;
+ return s && sscanf (s, "." HOST_WIDE_INT_PRINT_HEX_PURE, id) == 1;
}
/* Create file_data of each sub file id */
@@ -1008,7 +1005,7 @@ create_subid_section_table (void **slot, void *data)
struct lto_section_slot s_slot, *new_slot;
struct lto_section_slot *ls = *(struct lto_section_slot **)slot;
splay_tree file_ids = (splay_tree)data;
- unsigned id;
+ unsigned HOST_WIDE_INT id;
splay_tree_node nd;
void **hash_slot;
char *new_name;
@@ -1080,7 +1077,7 @@ static int lto_create_files_from_ids (splay_tree_node node, void *data)
lto_file_finalize (file_data, lw->file);
if (cgraph_dump_file)
- fprintf (cgraph_dump_file, "Creating file %s with sub id %x\n",
+ fprintf (cgraph_dump_file, "Creating file %s with sub id " HOST_WIDE_INT_PRINT_HEX "\n",
file_data->file_name, file_data->id);
file_data->next = *lw->file_data;
*lw->file_data = file_data;
diff --git a/gcc/toplev.c b/gcc/toplev.c
index 3688c09..e1a8b35 100644
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -141,6 +141,9 @@ static const char *flag_random_seed;
user has specified a particular random seed. */
unsigned local_tick;
+/* Random number for this compilation */
+HOST_WIDE_INT random_seed;
+
/* -f flags. */
/* Generate code for GNU or NeXT Objective-C runtime environment. */
@@ -251,7 +254,7 @@ announce_function (tree decl)
}
}
-/* Initialize local_tick with the time of day, or -1 if
+/* Initialize local_tick with a random number or -1 if
flag_random_seed is set. */
static void
@@ -286,24 +289,21 @@ init_local_tick (void)
static void
init_random_seed (void)
{
- unsigned HOST_WIDE_INT value;
- static char random_seed[HOST_BITS_PER_WIDE_INT / 4 + 3];
-
- value = local_tick ^ getpid ();
-
- sprintf (random_seed, HOST_WIDE_INT_PRINT_HEX, value);
- flag_random_seed = random_seed;
+ if (flag_random_seed)
+ random_seed = crc32_string (0, flag_random_seed);
+ else if (!random_seed)
+ random_seed = local_tick ^ getpid (); /* Old racey fallback method */
}
-/* Obtain the random_seed string. Unless NOINIT, initialize it if
+/* Obtain the random_seed. Unless NOINIT, initialize it if
it's not provided in the command line. */
-const char *
+HOST_WIDE_INT
get_random_seed (bool noinit)
{
if (!flag_random_seed && !noinit)
init_random_seed ();
- return flag_random_seed;
+ return random_seed;
}
/* Modify the random_seed string to VAL. Return its previous
@@ -314,6 +314,7 @@ set_random_seed (const char *val)
{
const char *old = flag_random_seed;
flag_random_seed = val;
+ random_seed = crc32_string (0, flag_random_seed);
return old;
}
diff --git a/gcc/toplev.h b/gcc/toplev.h
index 2455dc0..588cfdb 100644
--- a/gcc/toplev.h
+++ b/gcc/toplev.h
@@ -77,7 +77,7 @@ extern bool set_src_pwd (const char *);
/* Functions used to manipulate the random seed. */
-extern const char *get_random_seed (bool);
+extern HOST_WIDE_INT get_random_seed (bool);
extern const char *set_random_seed (const char *);
#endif /* ! GCC_TOPLEV_H */
diff --git a/gcc/tree.c b/gcc/tree.c
index a53c9f4..6a2e9fb 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -8749,11 +8749,11 @@ get_file_function_name (const char *type)
file = input_filename;
len = strlen (file);
- q = (char *) alloca (9 * 2 + len + 1);
+ q = (char *) alloca (9 + 17 + len + 1);
memcpy (q, file, len + 1);
- sprintf (q + len, "_%08X_%08X", crc32_string (0, name),
- crc32_string (0, get_random_seed (false)));
+ snprintf (q + len, 9 + 17 + 1, "_%08X_" HOST_WIDE_INT_PRINT_HEX,
+ crc32_string (0, name), get_random_seed (false));
p = q;
}
--
1.7.5.4