Two cleanup items for the sampling instrumentation interfaces. First,
rename variables from *rate* to *period*, since what is being specified
is a sampling period (time between recorded samples) not a rate.
Second, add flag __gcov_has_sampling to indicate when a file was
compiled with -fprofile-generate-sampling, and fuction
__gcov_sampling_enabled to return the state of this flag. The flag
is checked when a call is made to set the sampling period.
Bootstrapped and tested on x86_64-unknown-linux-gnu. Ok for google branches?
Thanks,
Teresa
2012-05-14 Teresa Johnson <tejohn...@google.com>
* libgcc/libgcov.c (__gcov_sampling_period): Rename variable from
"*rate*" to "*period*".
(gcov_sampling_period_initialized): Ditto.
(__gcov_set_sampling_period): Rename from __gcov_set_sampling_rate.
Check __gcov_has_sampling.
(__gcov_has_sampling): New variable.
(__gcov_sampling_enabled): New function.
(__gcov_init): Rename variables from "*rate*" to "*period*".
* gcc/doc/invoke.texi (profile-generate-sampling-period): Rename
from profile-generate-sampling-rate.
* gcc/tree-profile.c (gcov_sampling_period_decl): Rename from
gcov_sampling_rate_decl.
(gcov_has_sampling_decl): New variable.
(insert_if_then, add_sampling_wrapper): Rename variables from
"*rate*" to "*period*".
(gimple_init_instrumentation_sampling): Ditto, and add handling
for gcov_has_sampling_decl.
* gcc/params.def (profile-generate-sampling-period): Rename
from profile-generate-sampling-rate.
Index: libgcc/libgcov.c
===================================================================
--- libgcc/libgcov.c (revision 187470)
+++ libgcc/libgcov.c (working copy)
@@ -141,18 +141,26 @@ extern char * __gcov_pmu_profile_filename;
extern char * __gcov_pmu_profile_options;
extern gcov_unsigned_t __gcov_pmu_top_n_address;
-/* Sampling rate. */
-extern gcov_unsigned_t __gcov_sampling_rate;
-static int gcov_sampling_rate_initialized = 0;
-void __gcov_set_sampling_rate (unsigned int rate);
+/* Sampling period. */
+extern gcov_unsigned_t __gcov_sampling_period;
+extern gcov_unsigned_t __gcov_has_sampling;
+static int gcov_sampling_period_initialized = 0;
+void __gcov_set_sampling_period (unsigned int period);
+unsigned int __gcov_sampling_enabled ();
-/* Set sampling rate to RATE. */
+/* Set sampling period to PERIOD. */
-void __gcov_set_sampling_rate (unsigned int rate)
+void __gcov_set_sampling_period (unsigned int period)
{
- __gcov_sampling_rate = rate;
+ gcc_assert (__gcov_has_sampling);
+ __gcov_sampling_period = period;
}
+unsigned int __gcov_sampling_enabled ()
+{
+ return __gcov_has_sampling;
+}
+
/* Per thread sample counter. */
THREAD_PREFIX gcov_unsigned_t __gcov_sample_counter = 0;
@@ -659,16 +667,16 @@ gcov_clear (void)
void
__gcov_init (struct gcov_info *info)
{
- if (!gcov_sampling_rate_initialized)
+ if (!gcov_sampling_period_initialized)
{
- const char* env_value_str = getenv ("GCOV_SAMPLING_RATE");
+ const char* env_value_str = getenv ("GCOV_SAMPLING_PERIOD");
if (env_value_str)
{
int env_value_int = atoi(env_value_str);
if (env_value_int >= 1)
- __gcov_sampling_rate = env_value_int;
+ __gcov_sampling_period = env_value_int;
}
- gcov_sampling_rate_initialized = 1;
+ gcov_sampling_period_initialized = 1;
}
if (!info->version || !info->n_functions)
Index: gcc/doc/invoke.texi
===================================================================
--- gcc/doc/invoke.texi (revision 187470)
+++ gcc/doc/invoke.texi (working copy)
@@ -8335,12 +8335,12 @@ the profile feedback data files. See @option{-fpro
@opindex -fprofile-generate-sampling
Enable sampling for instrumented binaries. Instead of recording every event,
-record only every N-th event, where N (the sampling rate) can be set either
+record only every N-th event, where N (the sampling period) can be set either
at compile time using
-@option{--param profile-generate-sampling-rate=@var{value}}, or
-at execution start time through environment variable @samp{GCOV_SAMPLING_RATE}.
+@option{--param profile-generate-sampling-period=@var{value}}, or at
+execution start time through environment variable @samp{GCOV_SAMPLING_PERIOD}.
-At this time sampling applies only to branch counters. A sampling rate of 100
+At this time sampling applies only to branch counters. A sampling period of
100
decreases instrumentated binary slowdown from up to 20x for heavily threaded
applications down to around 2x. @option{-fprofile-correction} is always
needed with sampling.
Index: gcc/tree-profile.c
===================================================================
--- gcc/tree-profile.c (revision 187470)
+++ gcc/tree-profile.c (working copy)
@@ -165,9 +165,12 @@ static struct pointer_set_t *instrumentation_to_be
/* extern __thread gcov_unsigned_t __gcov_sample_counter */
static tree gcov_sample_counter_decl = NULL_TREE;
-/* extern gcov_unsigned_t __gcov_sampling_rate */
-static tree gcov_sampling_rate_decl = NULL_TREE;
+/* extern gcov_unsigned_t __gcov_sampling_period */
+static tree gcov_sampling_period_decl = NULL_TREE;
+/* extern gcov_unsigned_t __gcov_has_sampling */
+static tree gcov_has_sampling_decl = NULL_TREE;
+
/* forward declaration. */
void gimple_init_instrumentation_sampling (void);
@@ -200,7 +203,7 @@ insert_if_then (gimple stmt_start, gimple stmt_end
Into:
__gcov_sample_counter++;
- if (__gcov_sample_counter >= __gcov_sampling_rate)
+ if (__gcov_sample_counter >= __gcov_sampling_period)
{
__gcov_sample_counter = 0;
ORIGINAL CODE
@@ -214,7 +217,7 @@ add_sampling_wrapper (gimple stmt_start, gimple st
{
tree zero, one, tmp_var, tmp1, tmp2, tmp3;
gimple stmt_inc_counter1, stmt_inc_counter2, stmt_inc_counter3;
- gimple stmt_reset_counter, stmt_assign_rate, stmt_if;
+ gimple stmt_reset_counter, stmt_assign_period, stmt_if;
gimple_stmt_iterator gsi;
tmp_var = create_tmp_reg (get_gcov_unsigned_t (), "PROF_sample");
@@ -230,7 +233,7 @@ add_sampling_wrapper (gimple stmt_start, gimple st
zero = build_int_cst (get_gcov_unsigned_t (), 0);
stmt_reset_counter = gimple_build_assign (gcov_sample_counter_decl, zero);
tmp3 = make_ssa_name (tmp_var, NULL);
- stmt_assign_rate = gimple_build_assign (tmp3, gcov_sampling_rate_decl);
+ stmt_assign_period = gimple_build_assign (tmp3, gcov_sampling_period_decl);
stmt_if = gimple_build_cond (GE_EXPR, tmp2, tmp3, NULL_TREE, NULL_TREE);
/* Insert them for now in the original basic block. */
@@ -238,7 +241,7 @@ add_sampling_wrapper (gimple stmt_start, gimple st
gsi_insert_before (&gsi, stmt_inc_counter1, GSI_SAME_STMT);
gsi_insert_before (&gsi, stmt_inc_counter2, GSI_SAME_STMT);
gsi_insert_before (&gsi, stmt_inc_counter3, GSI_SAME_STMT);
- gsi_insert_before (&gsi, stmt_assign_rate, GSI_SAME_STMT);
+ gsi_insert_before (&gsi, stmt_assign_period, GSI_SAME_STMT);
gsi_insert_before (&gsi, stmt_reset_counter, GSI_SAME_STMT);
/* Insert IF block. */
@@ -293,27 +296,49 @@ add_sampling_to_edge_counters (void)
void
gimple_init_instrumentation_sampling (void)
{
- if (!gcov_sampling_rate_decl)
+ if (!gcov_sampling_period_decl)
{
- /* Define __gcov_sampling_rate regardless of -fprofile-generate-sampling.
- Otherwise the extern reference to it from libgcov becomes unmatched.
+ /* Define __gcov_sampling_period regardless of
+ -fprofile-generate-sampling. Otherwise the extern reference to
+ it from libgcov becomes unmatched.
*/
- gcov_sampling_rate_decl = build_decl (
+ gcov_sampling_period_decl = build_decl (
UNKNOWN_LOCATION,
VAR_DECL,
- get_identifier ("__gcov_sampling_rate"),
+ get_identifier ("__gcov_sampling_period"),
get_gcov_unsigned_t ());
- TREE_PUBLIC (gcov_sampling_rate_decl) = 1;
- DECL_ARTIFICIAL (gcov_sampling_rate_decl) = 1;
- DECL_COMDAT_GROUP (gcov_sampling_rate_decl)
- = DECL_ASSEMBLER_NAME (gcov_sampling_rate_decl);
- TREE_STATIC (gcov_sampling_rate_decl) = 1;
- DECL_INITIAL (gcov_sampling_rate_decl) = build_int_cst (
+ TREE_PUBLIC (gcov_sampling_period_decl) = 1;
+ DECL_ARTIFICIAL (gcov_sampling_period_decl) = 1;
+ DECL_COMDAT_GROUP (gcov_sampling_period_decl)
+ = DECL_ASSEMBLER_NAME (gcov_sampling_period_decl);
+ TREE_STATIC (gcov_sampling_period_decl) = 1;
+ DECL_INITIAL (gcov_sampling_period_decl) = build_int_cst (
get_gcov_unsigned_t (),
- PARAM_VALUE (PARAM_PROFILE_GENERATE_SAMPLING_RATE));
- varpool_finalize_decl (gcov_sampling_rate_decl);
+ PARAM_VALUE (PARAM_PROFILE_GENERATE_SAMPLING_PERIOD));
+ varpool_finalize_decl (gcov_sampling_period_decl);
}
+ if (!gcov_has_sampling_decl)
+ {
+ /* Initialize __gcov_has_sampling to 1 if -fprofile-generate-sampling
+ specified, 0 otherwise. Used by libgcov to determine whether
+ a request to set the sampling period makes sense. */
+ gcov_has_sampling_decl = build_decl (
+ UNKNOWN_LOCATION,
+ VAR_DECL,
+ get_identifier ("__gcov_has_sampling"),
+ get_gcov_unsigned_t ());
+ TREE_PUBLIC (gcov_has_sampling_decl) = 1;
+ DECL_ARTIFICIAL (gcov_has_sampling_decl) = 1;
+ DECL_COMDAT_GROUP (gcov_has_sampling_decl)
+ = DECL_ASSEMBLER_NAME (gcov_has_sampling_decl);
+ TREE_STATIC (gcov_has_sampling_decl) = 1;
+ DECL_INITIAL (gcov_has_sampling_decl) = build_int_cst (
+ get_gcov_unsigned_t (),
+ flag_profile_generate_sampling ? 1 : 0);
+ varpool_finalize_decl (gcov_has_sampling_decl);
+ }
+
if (flag_profile_generate_sampling && !instrumentation_to_be_sampled)
{
instrumentation_to_be_sampled = pointer_set_create ();
Index: gcc/params.def
===================================================================
--- gcc/params.def (revision 187470)
+++ gcc/params.def (working copy)
@@ -919,8 +919,8 @@ DEFPARAM (PARAM_MAX_LIPO_MEMORY,
"don't import aux files if memory consumption exceeds this value",
2400000, 0, 0)
-DEFPARAM (PARAM_PROFILE_GENERATE_SAMPLING_RATE,
- "profile-generate-sampling-rate",
+DEFPARAM (PARAM_PROFILE_GENERATE_SAMPLING_PERIOD,
+ "profile-generate-sampling-period",
"sampling rate with -fprofile-generate-sampling",
100, 0, 2000000000)
--
This patch is available for review at http://codereview.appspot.com/6210058
