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ifcvt.c (dead_or_predicable): Disable if-conversion when doing so is likely to kill a shrink-wrapping opportunity. 

* ifcvt.c (dead_or_predicable): Disable if-conversion when
	doing so is likely to kill a shrink-wrapping opportunity.

From-SVN: r180028
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Alan Modra 2011-10-15 21:06:00 +10:30 committed by Alan Modra
parent 387748de2f
commit ac5b90bdc0
2 changed files with 61 additions and 0 deletions
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3
gcc/ChangeLog
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@ -1,5 +1,8 @@
2011-10-15 Alan Modra <amodra@gmail.com>
* ifcvt.c (dead_or_predicable): Disable if-conversion when
doing so is likely to kill a shrink-wrapping opportunity.
PR rtl-optimization/49941
* jump.c (mark_jump_label_1): Set JUMP_LABEL for simple_return jumps.

58
gcc/ifcvt.c
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@ -4166,6 +4166,64 @@ dead_or_predicable (basic_block test_bb, basic_block merge_bb,
FOR_BB_INSNS (merge_bb, insn)
if (NONDEBUG_INSN_P (insn))
df_simulate_find_defs (insn, merge_set);
/* If shrink-wrapping, disable this optimization when test_bb is
the first basic block and merge_bb exits. The idea is to not
move code setting up a return register as that may clobber a
register used to pass function parameters, which then must be
saved in caller-saved regs. A caller-saved reg requires the
prologue, killing a shrink-wrap opportunity. */
if ((flag_shrink_wrap && HAVE_simple_return && !epilogue_completed)
&& ENTRY_BLOCK_PTR->next_bb == test_bb
&& single_succ_p (new_dest)
&& single_succ (new_dest) == EXIT_BLOCK_PTR
&& bitmap_intersect_p (df_get_live_in (new_dest), merge_set))
{
regset return_regs;
unsigned int i;
return_regs = BITMAP_ALLOC (&reg_obstack);
/* Start off with the intersection of regs used to pass
params and regs used to return values. */
for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
if (FUNCTION_ARG_REGNO_P (i)
&& targetm.calls.function_value_regno_p (i))
bitmap_set_bit (return_regs, INCOMING_REGNO (i));
bitmap_and_into (return_regs, df_get_live_out (ENTRY_BLOCK_PTR));
bitmap_and_into (return_regs, df_get_live_in (EXIT_BLOCK_PTR));
if (!bitmap_empty_p (return_regs))
{
FOR_BB_INSNS_REVERSE (new_dest, insn)
if (NONDEBUG_INSN_P (insn))
{
df_ref *def_rec;
unsigned int uid = INSN_UID (insn);
/* If this insn sets any reg in return_regs.. */
for (def_rec = DF_INSN_UID_DEFS (uid); *def_rec; def_rec++)
{
df_ref def = *def_rec;
unsigned r = DF_REF_REGNO (def);
if (bitmap_bit_p (return_regs, r))
break;
}
/* ..then add all reg uses to the set of regs
we're interested in. */
if (*def_rec)
df_simulate_uses (insn, return_regs);
}
if (bitmap_intersect_p (merge_set, return_regs))
{
BITMAP_FREE (return_regs);
BITMAP_FREE (merge_set);
return FALSE;
}
}
BITMAP_FREE (return_regs);
}
}
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