+2000-04-21 Zack Weinberg <zack@wolery.cumb.org>
+
+ * predict.c (estimate_probability): New heuristic: if a jump
+ branches around a block with no successors, predict it taken.
+ Disentangle control flow.
+
2000-04-20 Richard Henderson <rth@cygnus.com>
* loop.c (emit_iv_add_mult): Revert last change.
rtx last_insn = BLOCK_END (i);
rtx cond, earliest;
int prob = 0;
+ edge e;
if (GET_CODE (last_insn) != JUMP_INSN
|| ! condjump_p (last_insn) || simplejump_p (last_insn))
continue;
+ if (find_reg_note (last_insn, REG_BR_PROB, 0))
+ continue;
cond = get_condition (last_insn, &earliest);
if (! cond)
continue;
+ /* If the jump branches around a block with no successors,
+ predict it to be taken. */
+ prob = 0;
+ for (e = BASIC_BLOCK (i)->succ; e; e = e->succ_next)
+ if ((e->flags & EDGE_FALLTHRU) && e->dest->succ == NULL)
+ {
+ prob = REG_BR_PROB_BASE;
+ break;
+ }
+ if (prob)
+ {
+ REG_NOTES (last_insn)
+ = gen_rtx_EXPR_LIST (REG_BR_PROB, GEN_INT (prob),
+ REG_NOTES (last_insn));
+ continue;
+ }
+
/* Try "pointer heuristic."
A comparison ptr == 0 is predicted as false.
Similarly, a comparison ptr1 == ptr2 is predicted as false. */
- prob = 0;
switch (GET_CODE (cond))
{
case EQ:
default:
prob = 0;
}
- if (prob && ! find_reg_note (last_insn, REG_BR_PROB, 0))
+ if (prob)
+ {
REG_NOTES (last_insn)
= gen_rtx_EXPR_LIST (REG_BR_PROB, GEN_INT (prob),
REG_NOTES (last_insn));
+ continue;
+ }
/* Try "opcode heuristic."
EQ tests are usually false and NE tests are usually true. Also,
default:
prob = 0;
}
- if (! find_reg_note (last_insn, REG_BR_PROB, 0))
- REG_NOTES (last_insn)
- = gen_rtx_EXPR_LIST (REG_BR_PROB, GEN_INT (prob),
- REG_NOTES (last_insn));
+ REG_NOTES (last_insn)
+ = gen_rtx_EXPR_LIST (REG_BR_PROB, GEN_INT (prob),
+ REG_NOTES (last_insn));
}
}
\f