+2002-08-02 Alan Modra <amodra@bigpond.net.au>
+
+ * config/rs6000/rs6000.c (output_cbranch): Hint differently for power4.
+
2002-08-01 Daniel Jacobowitz <drow@mvista.com>
* Makefile.in ($(BUILD_PREFIX_1)ggc-none.o): Use $(GGC_H).
/* Maybe we have a guess as to how likely the branch is.
The old mnemonics don't have a way to specify this information. */
+ pred = "";
note = find_reg_note (insn, REG_BR_PROB, NULL_RTX);
if (note != NULL_RTX)
{
/* PROB is the difference from 50%. */
int prob = INTVAL (XEXP (note, 0)) - REG_BR_PROB_BASE / 2;
-
- /* For branches that are very close to 50%, assume not-taken. */
- if (abs (prob) > REG_BR_PROB_BASE / 20
- && ((prob > 0) ^ need_longbranch))
- pred = "+";
- else
- pred = "-";
+ bool always_hint = rs6000_cpu != PROCESSOR_POWER4;
+
+ /* Only hint for highly probable/improbable branches on newer
+ cpus as static prediction overrides processor dynamic
+ prediction. For older cpus we may as well always hint, but
+ assume not taken for branches that are very close to 50% as a
+ mispredicted taken branch is more expensive than a
+ mispredicted not-taken branch. */
+ if (always_hint
+ || abs (prob) > REG_BR_PROB_BASE / 100 * 48)
+ {
+ if (abs (prob) > REG_BR_PROB_BASE / 20
+ && ((prob > 0) ^ need_longbranch))
+ pred = "+";
+ else
+ pred = "-";
+ }
}
- else
- pred = "";
if (label == NULL)
s += sprintf (s, "{b%sr|b%slr%s} ", ccode, ccode, pred);