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cfgcleanup.c (label_is_jump_target_p): New function. 

* cfgcleanup.c (label_is_jump_target_p): New function.
	(try_optimize_cfg): Use label_is_jump_target_p to check if label is
	target of a JUMP_INSN from the preceding block.

From-SVN: r47825
This commit is contained in:
Richard Henderson 2001-12-09 17:09:42 -08:00 committed by John David Anglin
parent cca9fe755e
commit ec10f7c703
2 changed files with 46 additions and 3 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2001-12-09 Richard Henderson <rth@redhat.com>
* cfgcleanup.c (label_is_jump_target_p): New function.
(try_optimize_cfg): Use label_is_jump_target_p to check if label is
target of a JUMP_INSN from the preceding block.
Sun Dec 9 18:40:07 2001 Douglas B. Rupp <rupp@gnat.com>
* vmsdbgout.c (lookup_filename): Assign null string instead

43
gcc/cfgcleanup.c
View File

@ -69,6 +69,7 @@ static int flow_find_cross_jump PARAMS ((int, basic_block, basic_block,
rtx *, rtx *));
static bool delete_unreachable_blocks PARAMS ((void));
static bool label_is_jump_target_p PARAMS ((rtx, rtx));
static bool tail_recursion_label_p PARAMS ((rtx));
static void merge_blocks_move_predecessor_nojumps PARAMS ((basic_block,
basic_block));
@ -291,6 +292,38 @@ try_forward_edges (mode, b)
return changed;
}
/* Return true if LABEL is a target of JUMP_INSN. This applies only
to non-complex jumps. That is, direct unconditional, conditional,
and tablejumps, but not computed jumps or returns. It also does
not apply to the fallthru case of a conditional jump. */
static bool
label_is_jump_target_p (label, jump_insn)
rtx label, jump_insn;
{
rtx tmp = JUMP_LABEL (jump_insn);
if (label == tmp)
return true;
if (tmp != NULL_RTX
&& (tmp = NEXT_INSN (tmp)) != NULL_RTX
&& GET_CODE (tmp) == JUMP_INSN
&& (tmp = PATTERN (tmp),
GET_CODE (tmp) == ADDR_VEC
|| GET_CODE (tmp) == ADDR_DIFF_VEC))
{
rtvec vec = XVEC (tmp, GET_CODE (tmp) == ADDR_DIFF_VEC);
int i, veclen = GET_NUM_ELEM (vec);
for (i = 0; i < veclen; ++i)
if (XEXP (RTVEC_ELT (vec, i), 0) == label)
return true;
}
return false;
}
/* Return true if LABEL is used for tail recursion. */
static bool
@ -1162,10 +1195,14 @@ try_optimize_cfg (mode)
&& GET_CODE (b->head) == CODE_LABEL
&& (!(mode & CLEANUP_PRE_SIBCALL)
|| !tail_recursion_label_p (b->head))
/* If previous block ends with condjump jumping to next BB,
we can't delete the label. */
/* If the previous block ends with a branch to this block,
we can't delete the label. Normally this is a condjump
that is yet to be simplified, but if CASE_DROPS_THRU,
this can be a tablejump with some element going to the
same place as the default (fallthru). */
&& (b->pred->src == ENTRY_BLOCK_PTR
|| !reg_mentioned_p (b->head, b->pred->src->end)))
|| GET_CODE (b->pred->src->end) != JUMP_INSN
|| ! label_is_jump_target_p (b->head, b->pred->src->end)))
{
rtx label = b->head;
b->head = NEXT_INSN (b->head);