123 lines
5.2 KiB
Modula-2
123 lines
5.2 KiB
Modula-2
/* Definitions for the branch prediction routines in the GNU compiler.
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Copyright (C) 2001, 2003, 2004 Free Software Foundation, Inc.
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 2, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING. If not, write to the Free
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Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301, USA. */
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/* Before including this file, you should define a macro:
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DEF_PREDICTOR (ENUM, NAME, HITRATE)
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This macro will be called once for each predictor. The ENUM will
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be of type `enum predictor', and will enumerate all supported
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predictors. The order of DEF_PREDICTOR calls is important, as
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in the first match combining heuristics, the predictor appearing
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first in this file will win.
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NAME is used in the debugging output to determine predictor type.
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HITRATE is the probability that edge predicted by predictor as taken
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will be really taken (so it should be always above
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REG_BR_PROB_BASE / 2). */
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/* A value used as final outcome of all heuristics. */
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DEF_PREDICTOR (PRED_COMBINED, "combined", PROB_ALWAYS, 0)
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/* An outcome estimated by Dempster-Shaffer theory. */
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DEF_PREDICTOR (PRED_DS_THEORY, "DS theory", PROB_ALWAYS, 0)
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/* A combined heuristics using probability determined by first
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matching heuristics from this list. */
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DEF_PREDICTOR (PRED_FIRST_MATCH, "first match", PROB_ALWAYS, 0)
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/* Heuristic applying when no heuristic below applies. */
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DEF_PREDICTOR (PRED_NO_PREDICTION, "no prediction", PROB_ALWAYS, 0)
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/* Mark unconditional jump as taken. */
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DEF_PREDICTOR (PRED_UNCONDITIONAL, "unconditional jump", PROB_ALWAYS,
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PRED_FLAG_FIRST_MATCH)
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/* Use number of loop iterations determined by loop unroller to set
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probability. We don't want to use Dempster-Shaffer theory here,
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as the predictions is exact. */
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DEF_PREDICTOR (PRED_LOOP_ITERATIONS, "loop iterations", PROB_ALWAYS,
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PRED_FLAG_FIRST_MATCH)
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/* Hints dropped by user via __builtin_expect feature. */
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DEF_PREDICTOR (PRED_BUILTIN_EXPECT, "__builtin_expect", PROB_VERY_LIKELY,
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PRED_FLAG_FIRST_MATCH)
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/* Branch containing goto is probably not taken. */
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DEF_PREDICTOR (PRED_CONTINUE, "continue", HITRATE (56), 0)
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/* Branch to basic block containing call marked by noreturn attribute. */
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DEF_PREDICTOR (PRED_NORETURN, "noreturn call", HITRATE (99),
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PRED_FLAG_FIRST_MATCH)
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/* Loopback edge is taken. */
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DEF_PREDICTOR (PRED_LOOP_BRANCH, "loop branch", HITRATE (89),
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PRED_FLAG_FIRST_MATCH)
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/* Edge causing loop to terminate is probably not taken. */
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DEF_PREDICTOR (PRED_LOOP_EXIT, "loop exit", HITRATE (90),
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PRED_FLAG_FIRST_MATCH)
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/* Condition emitted by preconditiong code to ensure that variable
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setting number of iterations is greater than initial value of iterator. */
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DEF_PREDICTOR (PRED_LOOP_CONDITION, "loop condition", PROB_VERY_LIKELY, 0)
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/* Preconditioning makes linear list of branches. */
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DEF_PREDICTOR (PRED_LOOP_PRECONDITIONING, "loop preconditioning", PROB_VERY_LIKELY, 0)
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/* Copied condition for the first iteration of loop is probably true. */
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DEF_PREDICTOR (PRED_LOOP_HEADER, "loop header", HITRATE (64), 0)
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/* Pointers are usually not NULL. */
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DEF_PREDICTOR (PRED_POINTER, "pointer", HITRATE (81), 0)
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DEF_PREDICTOR (PRED_TREE_POINTER, "pointer (on trees)", HITRATE (81), 0)
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/* NE is probable, EQ not etc... */
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DEF_PREDICTOR (PRED_OPCODE_POSITIVE, "opcode values positive", HITRATE (79), 0)
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DEF_PREDICTOR (PRED_OPCODE_NONEQUAL, "opcode values nonequal", HITRATE (71), 0)
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DEF_PREDICTOR (PRED_FPOPCODE, "fp_opcode", HITRATE (90), 0)
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DEF_PREDICTOR (PRED_TREE_OPCODE_POSITIVE, "opcode values positive (on trees)", HITRATE (79), 0)
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DEF_PREDICTOR (PRED_TREE_OPCODE_NONEQUAL, "opcode values nonequal (on trees)", HITRATE (71), 0)
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DEF_PREDICTOR (PRED_TREE_FPOPCODE, "fp_opcode (on trees)", HITRATE (90), 0)
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/* Branch guarding call is probably taken. */
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DEF_PREDICTOR (PRED_CALL, "call", HITRATE (70), 0)
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/* Branch causing function to terminate is probably not taken. */
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DEF_PREDICTOR (PRED_EARLY_RETURN, "early return", HITRATE (67), 0)
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DEF_PREDICTOR (PRED_TREE_EARLY_RETURN, "early return (on trees)", HITRATE (67), 0)
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/* Branch containing goto is probably not taken. */
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DEF_PREDICTOR (PRED_GOTO, "goto", HITRATE (70), 0)
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/* Branch ending with return constant is probably not taken. */
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DEF_PREDICTOR (PRED_CONST_RETURN, "const return", HITRATE (95), 0)
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/* Branch ending with return negative constant is probably not taken. */
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DEF_PREDICTOR (PRED_NEGATIVE_RETURN, "negative return", HITRATE (96), 0)
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/* Branch ending with return; is probably not taken */
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DEF_PREDICTOR (PRED_NULL_RETURN, "null return", HITRATE (90), 0)
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/* Branches to a mudflap bounds check are extremely unlikely. */
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DEF_PREDICTOR (PRED_MUDFLAP, "mudflap check", HITRATE (99), 0)
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