On 11/28/2011 04:26 PM, Richard Henderson wrote:
> On 11/28/2011 03:05 PM, Richard Henderson wrote:
>> On 11/28/2011 02:16 PM, Alan Modra wrote:
>>> Hmm, I suppose you could argue that powerpc and others ought to not
>>> generate those three extra instructions when using the return value.
>>> I'll see about fixing powerpc.
>>
>> However, we can do better by considering the value to be stored in CR0...
>
> Try this and see if it generates the sort of code you want. Untested.
... actually, this one. There's no reason to differentiate between strong
and weak compare-and-swap when computing boolval.
r~
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index f01353b..5a33f91 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -17352,11 +17352,11 @@ rs6000_expand_atomic_compare_and_swap (rtx operands[])
retval = gen_reg_rtx (SImode);
mode = SImode;
}
+ else if (reg_overlap_mentioned_p (retval, oldval))
+ oldval = copy_to_reg (oldval);
rs6000_pre_atomic_barrier (mod_s);
- emit_move_insn (boolval, const0_rtx);
-
label1 = NULL_RTX;
if (!is_weak)
{
@@ -17374,28 +17374,23 @@ rs6000_expand_atomic_compare_and_swap (rtx operands[])
NULL_RTX, 1, OPTAB_LIB_WIDEN);
}
- x = gen_rtx_NE (VOIDmode, x, oldval);
- x = rs6000_generate_compare (x, mode);
+ cond = gen_reg_rtx (CCmode);
+ x = gen_rtx_COMPARE (CCmode, x, oldval);
+ emit_insn (gen_rtx_SET (VOIDmode, cond, x));
+
+ x = gen_rtx_NE (VOIDmode, cond, const0_rtx);
emit_unlikely_jump (x, label2);
x = newval;
if (mask)
x = rs6000_mask_atomic_subword (retval, newval, mask);
- cond = gen_reg_rtx (CCmode);
emit_store_conditional (mode, cond, mem, x);
- if (is_weak)
- {
- /* ??? It's either this or an unlikely jump over (set bool 1). */
- x = gen_rtx_EQ (SImode, cond, const0_rtx);
- emit_insn (gen_rtx_SET (VOIDmode, boolval, x));
- }
- else
+ if (!is_weak)
{
x = gen_rtx_NE (VOIDmode, cond, const0_rtx);
emit_unlikely_jump (x, label1);
- emit_move_insn (boolval, const1_rtx);
}
if (mod_f != MEMMODEL_RELAXED)
@@ -17408,6 +17403,10 @@ rs6000_expand_atomic_compare_and_swap (rtx operands[])
if (shift)
rs6000_finish_atomic_subword (operands[1], retval, shift);
+
+ /* In all cases, CR0 contains EQ on success, and NE on failure. */
+ x = gen_rtx_EQ (SImode, cond, const0_rtx);
+ emit_insn (gen_rtx_SET (VOIDmode, boolval, x));
}
/* Expand an atomic exchange operation. */
