procyberian/gcc
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

builtins.c (expand_builtin_expect_jump): Simplify logic.

Browse source 
* builtins.c (expand_builtin_expect_jump): Simplify logic. Handle
	conditional jumps that drop through to unconditional jumps or the
	end of the sequence.

From-SVN: r75780
This commit is contained in:
Roger Sayle 2004-01-13 01:32:42 +00:00 • committed by Roger Sayle
parent 3416f5c283
commit 04cc79bb89
2 changed files with 59 additions and 45 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

6
gcc/ChangeLog
View file

@ -1,3 +1,9 @@
2004-01-12 Roger Sayle <roger@eyesopen.com>
* builtins.c (expand_builtin_expect_jump): Simplify logic. Handle
conditional jumps that drop through to unconditional jumps or the
end of the sequence.
2004-01-13 Jan Hubicka <jh@suse.cz>
* alias.c (new_alias_set): Construct the alias_set varray.

98
gcc/builtins.c
View file

@ -4460,10 +4460,7 @@ expand_builtin_expect_jump (tree exp, rtx if_false_label, rtx if_true_label)
if (! if_false_label)
if_false_label = drop_through_label;
/* Now that the __builtin_expect has been validated, go through and add
the expect's to each of the conditional jumps. If we run into an
error, just give up and generate the 'safe' code of doing a SCC
operation and then doing a branch on that. */
/* Go through and add the expect's to each of the conditional jumps. */
insn = ret;
while (insn != NULL_RTX)
{
@ -4472,54 +4469,65 @@ expand_builtin_expect_jump (tree exp, rtx if_false_label, rtx if_true_label)
if (GET_CODE (insn) == JUMP_INSN && any_condjump_p (insn))
{
rtx ifelse = SET_SRC (pc_set (insn));
rtx label;
int taken;
rtx then_dest = XEXP (ifelse, 1);
rtx else_dest = XEXP (ifelse, 2);
int taken = -1;
if (GET_CODE (XEXP (ifelse, 1)) == LABEL_REF)
/* First check if we recognize any of the labels. */
if (GET_CODE (then_dest) == LABEL_REF
&& XEXP (then_dest, 1) == if_true_label)
taken = 1;
else if (GET_CODE (then_dest) == LABEL_REF
&& XEXP (then_dest, 1) == if_false_label)
taken = 0;
else if (GET_CODE (else_dest) == LABEL_REF
&& XEXP (else_dest, 1) == if_false_label)
taken = 1;
else if (GET_CODE (else_dest) == LABEL_REF
&& XEXP (else_dest, 1) == if_true_label)
taken = 0;
/* Otherwise check where we drop through. */
else if (else_dest == pc_rtx)
{
taken = 1;
label = XEXP (XEXP (ifelse, 1), 0);
}
/* An inverted jump reverses the probabilities. */
else if (GET_CODE (XEXP (ifelse, 2)) == LABEL_REF)
{
taken = 0;
label = XEXP (XEXP (ifelse, 2), 0);
}
/* We shouldn't have to worry about conditional returns during
the expansion stage, but handle it gracefully anyway. */
else if (GET_CODE (XEXP (ifelse, 1)) == RETURN)
{
taken = 1;
label = NULL_RTX;
}
/* An inverted return reverses the probabilities. */
else if (GET_CODE (XEXP (ifelse, 2)) == RETURN)
{
taken = 0;
label = NULL_RTX;
}
else
goto do_next_insn;
if (next && GET_CODE (next) == NOTE)
next = next_nonnote_insn (next);
/* If the test is expected to fail, reverse the
probabilities. */
if (integer_zerop (arg1))
taken = 1 - taken;
if (next && GET_CODE (next) == JUMP_INSN
&& any_uncondjump_p (next))
next = XEXP (SET_SRC (pc_set (next)), 1);
/* If we are jumping to the false label, reverse the
probabilities. */
if (label == NULL_RTX)
; /* conditional return */
else if (label == if_false_label)
taken = 1 - taken;
else if (label != if_true_label)
goto do_next_insn;
/* NEXT is either a CODE_LABEL, NULL_RTX or something
else that can't possibly match either target label. */
if (next == if_false_label)
taken = 1;
else if (next == if_true_label)
taken = 0;
}
else if (then_dest == pc_rtx)
{
if (next && GET_CODE (next) == NOTE)
next = next_nonnote_insn (next);
predict_insn_def (insn, PRED_BUILTIN_EXPECT, taken);
if (next && GET_CODE (next) == JUMP_INSN
&& any_uncondjump_p (next))
next = XEXP (SET_SRC (pc_set (next)), 1);
if (next == if_false_label)
taken = 0;
else if (next == if_true_label)
taken = 1;
}
if (taken != -1)
{
/* If the test is expected to fail, reverse the
probabilities. */
if (integer_zerop (arg1))
taken = 1 - taken;
predict_insn_def (insn, PRED_BUILTIN_EXPECT, taken);
}
}
do_next_insn:
insn = next;
}
}