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reorg.c (mostly_true_jump): Clean up code depending on LABEL_OUTSIDE_LOOP_P and loop notes. 

* reorg.c (mostly_true_jump): Clean up code depending on
	LABEL_OUTSIDE_LOOP_P and loop notes.  Remove code doing
	poor man's branch prediction, instead rely on REG_BR_PROB
	notes to be available.

From-SVN: r108653
This commit is contained in:
Steven Bosscher 2005-12-16 15:38:19 +00:00 committed by Steven Bosscher
parent 5adb25cf83
commit 52ba2f6d14
2 changed files with 10 additions and 53 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,10 @@
2005-12-16 Steven Bosscher <stevenb@suse.de>
* reorg.c (mostly_true_jump): Clean up code depending on
LABEL_OUTSIDE_LOOP_P and loop notes. Remove code doing
poor man's branch prediction, instead rely on REG_BR_PROB
notes to be available.
2005-12-16 Jakub Jelinek <jakub@redhat.com>
PR rtl-optimization/24899

56
gcc/reorg.c
View File

@ -964,8 +964,7 @@ mostly_true_jump (rtx jump_insn, rtx condition)
{
rtx target_label = JUMP_LABEL (jump_insn);
rtx insn, note;
int rare_dest = rare_destination (target_label);
int rare_fallthrough = rare_destination (NEXT_INSN (jump_insn));
int rare_dest, rare_fallthrough;
/* If branch probabilities are available, then use that number since it
always gives a correct answer. */
@ -984,32 +983,10 @@ mostly_true_jump (rtx jump_insn, rtx condition)
return -1;
}
/* ??? Ought to use estimate_probability instead. */
/* If this is a branch outside a loop, it is highly unlikely. */
if (GET_CODE (PATTERN (jump_insn)) == SET
&& GET_CODE (SET_SRC (PATTERN (jump_insn))) == IF_THEN_ELSE
&& ((GET_CODE (XEXP (SET_SRC (PATTERN (jump_insn)), 1)) == LABEL_REF
&& LABEL_OUTSIDE_LOOP_P (XEXP (SET_SRC (PATTERN (jump_insn)), 1)))
|| (GET_CODE (XEXP (SET_SRC (PATTERN (jump_insn)), 2)) == LABEL_REF
&& LABEL_OUTSIDE_LOOP_P (XEXP (SET_SRC (PATTERN (jump_insn)), 2)))))
return -1;
if (target_label)
{
/* If this is the test of a loop, it is very likely true. We scan
backwards from the target label. If we find a NOTE_INSN_LOOP_BEG
before the next real insn, we assume the branch is to the top of
the loop. */
for (insn = PREV_INSN (target_label);
insn && NOTE_P (insn);
insn = PREV_INSN (insn))
if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
return 2;
}
/* Look at the relative rarities of the fallthrough and destination. If
they differ, we can predict the branch that way. */
rare_dest = rare_destination (target_label);
rare_fallthrough = rare_destination (NEXT_INSN (jump_insn));
switch (rare_fallthrough - rare_dest)
{
@ -1030,33 +1007,6 @@ mostly_true_jump (rtx jump_insn, rtx condition)
if (condition == 0)
return 0;
/* EQ tests are usually false and NE tests are usually true. Also,
most quantities are positive, so we can make the appropriate guesses
about signed comparisons against zero. */
switch (GET_CODE (condition))
{
case CONST_INT:
/* Unconditional branch. */
return 1;
case EQ:
return 0;
case NE:
return 1;
case LE:
case LT:
if (XEXP (condition, 1) == const0_rtx)
return 0;
break;
case GE:
case GT:
if (XEXP (condition, 1) == const0_rtx)
return 1;
break;
default:
break;
}
/* Predict backward branches usually take, forward branches usually not. If
we don't know whether this is forward or backward, assume the branch
will be taken, since most are. */