/* Definitions for the branch prediction routines in the GNU compiler.
- Copyright (C) 2001, 2003, 2004 Free Software Foundation, Inc.
+ Copyright (C) 2001-2016 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 2, or (at your option) any later
+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
for more details.
You should have received a copy of the GNU General Public License
-along with GCC; see the file COPYING. If not, write to the Free
-Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
-02110-1301, USA. */
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
/* Before including this file, you should define a macro:
HITRATE is the probability that edge predicted by predictor as taken
will be really taken (so it should be always above
REG_BR_PROB_BASE / 2). */
-
+
/* A value used as final outcome of all heuristics. */
DEF_PREDICTOR (PRED_COMBINED, "combined", PROB_ALWAYS, 0)
/* An outcome estimated by Dempster-Shaffer theory. */
DEF_PREDICTOR (PRED_DS_THEORY, "DS theory", PROB_ALWAYS, 0)
-/* An combined heuristics using probability determined by first
+/* A combined heuristics using probability determined by first
matching heuristics from this list. */
DEF_PREDICTOR (PRED_FIRST_MATCH, "first match", PROB_ALWAYS, 0)
DEF_PREDICTOR (PRED_UNCONDITIONAL, "unconditional jump", PROB_ALWAYS,
PRED_FLAG_FIRST_MATCH)
-/* Use number of loop iterations determined by loop unroller to set
- probability. We don't want to use Dempster-Shaffer theory here,
- as the predictions is exact. */
+/* Use number of loop iterations determined by # of iterations
+ analysis to set probability. We don't want to use Dempster-Shaffer
+ theory here, as the predictions is exact. */
DEF_PREDICTOR (PRED_LOOP_ITERATIONS, "loop iterations", PROB_ALWAYS,
PRED_FLAG_FIRST_MATCH)
-/* Hints dropped by user via __builtin_expect feature. */
+/* Assume that any given atomic operation has low contention,
+ and thus the compare-and-swap operation succeeds. */
+DEF_PREDICTOR (PRED_COMPARE_AND_SWAP, "compare and swap", PROB_VERY_LIKELY,
+ PRED_FLAG_FIRST_MATCH)
+
+/* Hints dropped by user via __builtin_expect feature. Note: the
+ probability of PROB_VERY_LIKELY is now overwritten by param
+ builtin_expect_probability with a default value of HITRATE(90).
+ Refer to param.def for details. */
DEF_PREDICTOR (PRED_BUILTIN_EXPECT, "__builtin_expect", PROB_VERY_LIKELY,
PRED_FLAG_FIRST_MATCH)
+/* Use number of loop iterations guessed by the contents of the loop. */
+DEF_PREDICTOR (PRED_LOOP_ITERATIONS_GUESSED, "guessed loop iterations",
+ PROB_ALWAYS, PRED_FLAG_FIRST_MATCH)
+
+/* Use number of loop iterations guessed by the contents of the loop. */
+DEF_PREDICTOR (PRED_LOOP_ITERATIONS_MAX, "guessed loop iterations",
+ PROB_ALWAYS, PRED_FLAG_FIRST_MATCH)
+
/* Branch containing goto is probably not taken. */
-DEF_PREDICTOR (PRED_CONTINUE, "continue", HITRATE (56), 0)
+DEF_PREDICTOR (PRED_CONTINUE, "continue", HITRATE (67), 0)
/* Branch to basic block containing call marked by noreturn attribute. */
-DEF_PREDICTOR (PRED_NORETURN, "noreturn call", HITRATE (99),
+DEF_PREDICTOR (PRED_NORETURN, "noreturn call", PROB_VERY_LIKELY,
PRED_FLAG_FIRST_MATCH)
-/* Loopback edge is taken. */
-DEF_PREDICTOR (PRED_LOOP_BRANCH, "loop branch", HITRATE (89),
+/* Branch to basic block containing call marked by cold function attribute. */
+DEF_PREDICTOR (PRED_COLD_FUNCTION, "cold function call", PROB_VERY_LIKELY,
PRED_FLAG_FIRST_MATCH)
/* Edge causing loop to terminate is probably not taken. */
-DEF_PREDICTOR (PRED_LOOP_EXIT, "loop exit", HITRATE (90),
+DEF_PREDICTOR (PRED_LOOP_EXIT, "loop exit", HITRATE (85),
PRED_FLAG_FIRST_MATCH)
-/* Condition emitted by preconditiong code to ensure that variable
- setting number of iterations is greater than initial value of iterator. */
-DEF_PREDICTOR (PRED_LOOP_CONDITION, "loop condition", PROB_VERY_LIKELY, 0)
-
-/* Preconditioning makes linear list of branches. */
-DEF_PREDICTOR (PRED_LOOP_PRECONDITIONING, "loop preconditioning", PROB_VERY_LIKELY, 0)
-
-/* Copied condition for the first iteration of loop is probably true. */
-DEF_PREDICTOR (PRED_LOOP_HEADER, "loop header", HITRATE (64), 0)
+/* Edge causing loop to terminate by computing value used by later
+ conditional. */
+DEF_PREDICTOR (PRED_LOOP_EXTRA_EXIT, "extra loop exit", HITRATE (83),
+ PRED_FLAG_FIRST_MATCH)
/* Pointers are usually not NULL. */
-DEF_PREDICTOR (PRED_POINTER, "pointer", HITRATE (81), 0)
-DEF_PREDICTOR (PRED_TREE_POINTER, "pointer (on trees)", HITRATE (81), 0)
+DEF_PREDICTOR (PRED_POINTER, "pointer", HITRATE (70), 0)
+DEF_PREDICTOR (PRED_TREE_POINTER, "pointer (on trees)", HITRATE (70), 0)
/* NE is probable, EQ not etc... */
-DEF_PREDICTOR (PRED_OPCODE_POSITIVE, "opcode values positive", HITRATE (79), 0)
-DEF_PREDICTOR (PRED_OPCODE_NONEQUAL, "opcode values nonequal", HITRATE (71), 0)
+DEF_PREDICTOR (PRED_OPCODE_POSITIVE, "opcode values positive", HITRATE (64), 0)
+DEF_PREDICTOR (PRED_OPCODE_NONEQUAL, "opcode values nonequal", HITRATE (66), 0)
DEF_PREDICTOR (PRED_FPOPCODE, "fp_opcode", HITRATE (90), 0)
-DEF_PREDICTOR (PRED_TREE_OPCODE_POSITIVE, "opcode values positive (on trees)", HITRATE (79), 0)
-DEF_PREDICTOR (PRED_TREE_OPCODE_NONEQUAL, "opcode values nonequal (on trees)", HITRATE (71), 0)
+DEF_PREDICTOR (PRED_TREE_OPCODE_POSITIVE, "opcode values positive (on trees)", HITRATE (64), 0)
+DEF_PREDICTOR (PRED_TREE_OPCODE_NONEQUAL, "opcode values nonequal (on trees)", HITRATE (66), 0)
DEF_PREDICTOR (PRED_TREE_FPOPCODE, "fp_opcode (on trees)", HITRATE (90), 0)
/* Branch guarding call is probably taken. */
-DEF_PREDICTOR (PRED_CALL, "call", HITRATE (70), 0)
-
-/* Branch causing function to terminate is probably not taken. */
-DEF_PREDICTOR (PRED_EARLY_RETURN, "early return", HITRATE (67), 0)
-DEF_PREDICTOR (PRED_TREE_EARLY_RETURN, "early return (on trees)", HITRATE (67), 0)
-
-/* Branch containing goto is probably not taken. */
+DEF_PREDICTOR (PRED_CALL, "call", HITRATE (67), 0)
+
+/* Recursive calls are usually not taken or the function will recurse indefinitely. */
+DEF_PREDICTOR (PRED_RECURSIVE_CALL, "recursive call", HITRATE (75), 0)
+
+/* Branch causing function to terminate is probably not taken.
+ FIXME: early return currently predicts code:
+ int foo (int a)
+ {
+ if (a)
+ bar();
+ else
+ bar2();
+ }
+ even though there is no return statement involved. We probably want to track
+ this from FE or retire the predictor. */
+DEF_PREDICTOR (PRED_TREE_EARLY_RETURN, "early return (on trees)", HITRATE (54), 0)
+
+/* Branch containing goto is probably not taken.
+ FIXME: Currently not used. */
DEF_PREDICTOR (PRED_GOTO, "goto", HITRATE (70), 0)
/* Branch ending with return constant is probably not taken. */
-DEF_PREDICTOR (PRED_CONST_RETURN, "const return", HITRATE (95), 0)
+DEF_PREDICTOR (PRED_CONST_RETURN, "const return", HITRATE (69), 0)
/* Branch ending with return negative constant is probably not taken. */
-DEF_PREDICTOR (PRED_NEGATIVE_RETURN, "negative return", HITRATE (96), 0)
+DEF_PREDICTOR (PRED_NEGATIVE_RETURN, "negative return", HITRATE (98), 0)
/* Branch ending with return; is probably not taken */
-DEF_PREDICTOR (PRED_NULL_RETURN, "null return", HITRATE (90), 0)
+DEF_PREDICTOR (PRED_NULL_RETURN, "null return", HITRATE (91), 0)
+
+/* Branches to compare induction variable to a loop bound is
+ extremely likely. */
+DEF_PREDICTOR (PRED_LOOP_IV_COMPARE_GUESS, "guess loop iv compare",
+ HITRATE (98), 0)
+
+/* Use number of loop iterations determined by # of iterations analysis
+ to set probability of branches that compares IV to loop bound variable. */
+DEF_PREDICTOR (PRED_LOOP_IV_COMPARE, "loop iv compare", PROB_VERY_LIKELY,
+ PRED_FLAG_FIRST_MATCH)
+
+/* Branches to hot labels are likely. */
+DEF_PREDICTOR (PRED_HOT_LABEL, "hot label", HITRATE (85), 0)
+
+/* Branches to cold labels are extremely unlikely. */
+DEF_PREDICTOR (PRED_COLD_LABEL, "cold label", PROB_VERY_LIKELY,
+ PRED_FLAG_FIRST_MATCH)
+
+
+/* The following predictors are used in Fortran. */
+
+/* Branch leading to an integer overflow are extremely unlikely. */
+DEF_PREDICTOR (PRED_FORTRAN_OVERFLOW, "Fortran overflow", PROB_ALWAYS,
+ PRED_FLAG_FIRST_MATCH)
-/* Branches to a mudflap bounds check are extremely unlikely. */
-DEF_PREDICTOR (PRED_MUDFLAP, "mudflap check", HITRATE (99), 0)
+/* Branch leading to a failure status are unlikely. This can occur for out
+ of memory. This predictor only occurs when the user explicitly asked
+ for a return status. By default, the code aborts,
+ which is handled via PRED_NORETURN. */
+DEF_PREDICTOR (PRED_FORTRAN_FAIL_ALLOC, "Fortran fail alloc", PROB_VERY_LIKELY, 0)
+
+/* Predictor is used for an allocation of an already allocated memory or
+ deallocating an already deallocated allocatable. */
+DEF_PREDICTOR (PRED_FORTRAN_REALLOC, \
+ "Fortran repeated allocation/deallocation", PROB_LIKELY, 0)
+
+/* Branch leading to an I/O failure status are unlikely. This predictor is
+ used for I/O failures such as for invalid unit numbers. This predictor
+ only occurs when the user explicitly asked for a return status. By default,
+ the code aborts, which is handled via PRED_NORETURN. */
+DEF_PREDICTOR (PRED_FORTRAN_FAIL_IO, "Fortran fail IO", HITRATE (85), 0)
+
+/* Branch leading to a run-time warning message which is printed only once
+ are unlikely. The print-warning branch itself can be likely or unlikely. */
+DEF_PREDICTOR (PRED_FORTRAN_WARN_ONCE, "Fortran warn once", HITRATE (75), 0)
+
+/* Branch belonging to a zero-sized array. */
+DEF_PREDICTOR (PRED_FORTRAN_SIZE_ZERO, "Fortran zero-sized array", \
+ HITRATE (99), 0)
+
+/* Branch belonging to an invalid bound index, in a context where it is
+ standard conform and well defined but rather pointless and, hence, rather
+ unlikely to occur. */
+DEF_PREDICTOR (PRED_FORTRAN_INVALID_BOUND, "Fortran invalid bound", \
+ HITRATE (90), 0)
+
+/* Branch belonging to the handling of absent optional arguments. This
+ predictor is used when an optional dummy argument, associated with an
+ absent argument, is passed on as actual argument to another procedure,
+ which in turn has an optional argument. */
+DEF_PREDICTOR (PRED_FORTRAN_ABSENT_DUMMY, "Fortran absent dummy", \
+ HITRATE (60), 0)
+
+/* Fortran DO statement generates a pre-header guard:
+ empty = (step > 0 ? to < from : to > from), which can be predicted
+ to be very likely. */
+DEF_PREDICTOR (PRED_FORTRAN_LOOP_PREHEADER, "Fortran loop preheader", \
+ HITRATE (99), 0)
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