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1.8.1.1
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GCC Middle and Back End API Reference
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| static bool | error_found = false |
| static pointer_map_t * | cgraph_node_map |
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The overall number of invocations of the counter should match execution count of basic block. Report it as error rather than internal error as it might mean that user has misused the profile somehow.
References error_at().
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Perform sanity check on the indirect call target. Due to race conditions, false function target may be attributed to an indirect call site. If the call expression type mismatches with the target function's type, expand_call may ICE. Here we only do very minimal sanity check just to make compiler happy. Returns true if TARGET is considered ok for call CALL_STMT.
| void del_node_map | ( | void | ) |
Delete the CGRAPH_NODE_MAP.
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Dump information about HIST to DUMP_FILE.
Referenced by gimple_move_stmt_histograms().
| void dump_histograms_for_stmt | ( | ) |
Dump all histograms attached to STMT to DUMP_FILE.
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Return cgraph node for function with pid
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Helper function for verify_histograms. For each histogram reachable via htab walk verify that it was reached via statement walk.
| void free_histograms | ( | void | ) |
References current_function_decl, dump_enabled_p(), dump_printf_loc(), and gimple_location().
| void gimple_add_histogram_value | ( | struct function * | fun, |
| gimple | stmt, | ||
| histogram_value | hist | ||
| ) |
Add histogram for STMT.
References gimple_histogram_value(), histogram_value_t::hvalue, histogram_value_t::next, and set_histogram_value().
Referenced by gimple_remove_stmt_histograms().
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Allocate histogram value.
Referenced by gimple_remove_stmt_histograms(), and stringop_block_profile().
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@verbatim
Transformations based on profile information for values. Copyright (C) 2003-2013 Free Software Foundation, Inc.
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.
GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with GCC; see the file COPYING3. If not see http://www.gnu.org/licenses/.
In this file value profile based optimizations are placed. Currently the
following optimizations are implemented (for more detailed descriptions
see comments at value_profile_transformations):
1) Division/modulo specialization. Provided that we can determine that the
operands of the division have some special properties, we may use it to
produce more effective code.
2) Indirect/virtual call specialization. If we can determine most
common function callee in indirect/virtual call. We can use this
information to improve code effectiveness (especially info for
the inliner).
3) Speculative prefetching. If we are able to determine that the difference
between addresses accessed by a memory reference is usually constant, we
may add the prefetch instructions.
FIXME: This transformation was removed together with RTL based value
profiling.
Value profiling internals
==========================
Every value profiling transformation starts with defining what values
to profile. There are different histogram types (see HIST_TYPE_* in
value-prof.h) and each transformation can request one or more histogram
types per GIMPLE statement. The function gimple_find_values_to_profile()
collects the values to profile in a vec, and adds the number of counters
required for the different histogram types.
For a -fprofile-generate run, the statements for which values should be
recorded, are instrumented in instrument_values(). The instrumentation
is done by helper functions that can be found in tree-profile.c, where
new types of histograms can be added if necessary.
After a -fprofile-use, the value profiling data is read back in by
compute_value_histograms() that translates the collected data to
histograms and attaches them to the profiled statements via
gimple_add_histogram_value(). Histograms are stored in a hash table
that is attached to every intrumented function, see VALUE_HISTOGRAMS
in function.h.
The value-profile transformations driver is the function
gimple_value_profile_transformations(). It traverses all statements in
the to-be-transformed function, and looks for statements with one or
more histograms attached to it. If a statement has histograms, the
transformation functions are called on the statement.
Limitations / FIXME / TODO:
* Only one histogram of each type can be associated with a statement.
* Currently, HIST_TYPE_CONST_DELTA is not implemented.
(This type of histogram was originally used to implement a form of
stride profiling based speculative prefetching to improve SPEC2000
scores for memory-bound benchmarks, mcf and equake. However, this
was an RTL value-profiling transformation, and those have all been
removed.)
* Some value profile transformations are done in builtins.c (?!)
* Updating of histograms needs some TLC.
* The value profiling code could be used to record analysis results
from non-profiling (e.g. VRP).
* Adding new profilers should be simplified, starting with a cleanup
of what-happens-where andwith making gimple_find_values_to_profile
and gimple_value_profile_transformations table-driven, perhaps...
Generate code for transformation 1 (with parent gimple assignment STMT and probability of taking the optimal path PROB, which is equivalent to COUNT/ALL within roundoff error). This generates the result into a temp and returns the temp; it does not replace or alter the original STMT.
Fix CFG.
Edge e23 connects bb2 to bb3, etc.
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Do transform 1) on INSN if applicable.
We require that count is at least half of all; this means
that for the transformation to fire the value must be constant
at least 50% of time (and 75% gives the guarantee of usage). Compute probability of taking the optimal path.
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Find values inside STMT for that we want to measure histograms for division/modulo optimization.
Check for the case where the divisor is the same value most
of the time. For mod, check whether it is not often a noop (or replaceable by
a few subtractions). Check for a special case where the divisor is power of 2.
| void gimple_duplicate_stmt_histograms | ( | struct function * | fun, |
| gimple | stmt, | ||
| struct function * | ofun, | ||
| gimple | ostmt | ||
| ) |
Duplicate all histograms associates with OSTMT to STMT.
References gimple_histogram_value(), histogram_value_t::hvalue, histogram_value_t::next, set_histogram_value(), and histogram_value_t::stmt.
Referenced by gimple_redirect_edge_and_branch(), and gsi_split_seq_before().
| void gimple_find_values_to_profile | ( | ) |
| histogram_value gimple_histogram_value | ( | ) |
Get histogram list for STMT.
References histogram_value_t::hvalue, histogram_value_t::next, and set_histogram_value().
Referenced by gimple_add_histogram_value(), gimple_duplicate_stmt_histograms(), and visit_hist().
| histogram_value gimple_histogram_value_of_type | ( | struct function * | fun, |
| gimple | stmt, | ||
| enum hist_type | type | ||
| ) |
Lookup histogram of type TYPE in the STMT.
References histogram_value_t::counters, histogram_value_t::hdata, HIST_TYPE_INTERVAL, histogram_value_t::hvalue, histogram_value_t::intvl, and histogram_value_t::type.
| gimple gimple_ic | ( | gimple | icall_stmt, |
| struct cgraph_node * | direct_call, | ||
| int | prob, | ||
| gcov_type | count, | ||
| gcov_type | all | ||
| ) |
Do transformation
if (actual_callee_address == address_of_most_common_function/method)
do direct call
else
old call Fix CFG.
Edge e_cd connects cond_bb to dcall_bb, etc; note the first letters.
Do not disturb existing EH edges from the indirect call.
The indirect call might be noreturn.
Insert PHI node for the call result if necessary.
Build an EH edge for the direct call if necessary.
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The order of CHECK_COUNTER calls is important -
since check_counter can correct the third parameter
and we want to make count <= all <= bb_all.
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Find calls inside STMT for that we want to measure histograms for indirect/virtual call optimization.
References HIST_TYPE_CONST_DELTA, HIST_TYPE_INDIR_CALL, HIST_TYPE_INTERVAL, HIST_TYPE_POW2, and HIST_TYPE_SINGLE_VALUE.
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Generate code for transformation 2 (with parent gimple assign STMT and probability of taking the optimal path PROB, which is equivalent to COUNT/ALL within roundoff error). This generates the result into a temp and returns the temp; it does not replace or alter the original STMT.
tmp2 == op2-1 inherited from previous block.
Fix CFG.
Edge e23 connects bb2 to bb3, etc.
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Do transform 2) on INSN if applicable.
We require that we hit a power of 2 at least half of all evaluations.
Compute probability of taking the optimal path.
References print_gimple_stmt().
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Generate code for transformations 3 and 4 (with parent gimple assign STMT, and NCOUNTS the number of cases to support. Currently only NCOUNTS==0 or 1 is supported and this is built into this interface. The probabilities of taking the optimal paths are PROB1 and PROB2, which are equivalent to COUNT1/ALL and COUNT2/ALL respectively within roundoff error). This generates the result into a temp and returns the temp; it does not replace or alter the original STMT.
FIXME: Generalize the interface to handle NCOUNTS > 1.
Fallback case.
Fix CFG.
Edge e23 connects bb2 to bb3, etc.
However block 3 is optional; if it is not there, references
to 3 really refer to block 2.
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Do transforms 3) and 4) on the statement pointed-to by SI if applicable.
Compute probability of taking the optimal path.
We require that we use just subtractions in at least 50% of all
evaluations. Compute probability of taking the optimal path(s).
In practice, "steps" is always 2. This interface reflects this,
and will need to be changed if "steps" can change.
| void gimple_move_stmt_histograms | ( | ) |
Move all histograms associated with OSTMT to STMT.
The following three statements can't be reordered,
because histogram hashtab relies on stmt field value
for finding the exact slot.
References debug_gimple_stmt(), dump_histogram_value(), error(), histogram_value_t::hvalue, pointer_set_contains(), histogram_value_t::stmt, and visited.
| void gimple_remove_histogram_value | ( | struct function * | fun, |
| gimple | stmt, | ||
| histogram_value | hist | ||
| ) |
Remove histogram HIST from STMT's histogram list.
References histogram_value_t::hvalue, and histogram_value_t::next.
| void gimple_remove_stmt_histograms | ( | ) |
Remove all histograms associated with STMT.
References histogram_value_t::counters, gimple_add_histogram_value(), gimple_alloc_histogram_value(), histogram_value_t::hvalue, memcpy(), histogram_value_t::n_counters, histogram_value_t::stmt, and histogram_value_t::type.
Referenced by gsi_split_seq_before().
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Convert stringop (..., vcall_size)
into
if (vcall_size == icall_size)
stringop (..., icall_size);
else
stringop (..., vcall_size);
assuming we'll propagate a true constant into ICALL_SIZE later. Fix CFG.
Edge e_ci connects cond_bb to icall_bb, etc.
Insert PHI node for the call result if necessary.
Because these are all string op builtins, they're all nothrow.
References add_phi_arg(), create_phi_node(), duplicate_ssa_name(), gimple_call_lhs(), and gimple_call_set_lhs().
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Find values inside STMT for that we want to measure histograms for division/modulo optimization.
We require that count is at least half of all; this means
that for the transformation to fire the value must be constant
at least 80% of time.
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Find values inside STMT for that we want to measure histograms for string operations.
| bool gimple_value_profile_transformations | ( | void | ) |
GIMPLE based transformations.
Transformations:
The order of things in this conditional controls which
transformation is used when more than one is applicable. It is expected that any code added by the transformations
will be added before the current statement, and that the
current statement remain valid (although possibly
modified) upon return. Original statement may no longer be in the same block.
References gimple_bb(), gsi_for_stmt(), and gsi_stmt().
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Find values inside STMT for that we want to measure histograms and adds them to list VALUES.
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Return nonzero if statement for histogram_value X is Y.
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Hash value for histogram.
| void init_node_map | ( | ) |
Initialize map from PROFILE_ID to CGRAPH_NODE. When LOCAL is true, the PROFILE_IDs are computed. when it is false we assume that the PROFILE_IDs was already assigned.
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@verbatim
Return true if the stringop CALL with FNDECL shall be profiled. SIZE_ARG be set to the argument index for the size of the string operation.
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Set histogram for STMT.
Referenced by gimple_add_histogram_value(), gimple_duplicate_stmt_histograms(), and gimple_histogram_value().
| void stream_in_histogram_value | ( | ) |
Dump information about HIST to DUMP_FILE.
| void stream_out_histogram_value | ( | ) |
Dump information about HIST to DUMP_FILE.
| void stringop_block_profile | ( | gimple | stmt, |
| unsigned int * | expected_align, | ||
| HOST_WIDE_INT * | expected_size | ||
| ) |
Even if we can hold bigger value in SIZE, INT_MAX
is safe "infinity" for code generation strategies.
References cfun, gimple_alloc_histogram_value(), histogram_value_t::hdata, HIST_TYPE_INTERVAL, HIST_TYPE_POW2, and histogram_value_t::intvl.
| DEBUG_FUNCTION void verify_histograms | ( | void | ) |
Verify sanity of the histograms.
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Helper function for verify_histograms. For each histogram reachable via htab walk verify that it was reached via statement walk.
References cfun, error(), gimple_histogram_value(), gsi_end_p(), gsi_next(), gsi_start_bb(), gsi_stmt(), histogram_value_t::hvalue, histogram_value_t::next, pointer_set_create(), and histogram_value_t::stmt.
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Referenced by cgraph_edge_cannot_lead_to_return().
1.8.1.1