On 10 June 2014 19:01, Steven Bosscher <stevenb....@gmail.com> wrote:
> On Tue, Jun 10, 2014 at 11:55 AM, Zhenqiang Chen wrote:
>>
>> * loop-invariant.c (find_invariant_insn): Skip invariants, which
>> can not make a valid insn during replacement in move_invariant_reg.
>>
>> --- a/gcc/loop-invariant.c
>> +++ b/gcc/loop-invariant.c
>> @@ -881,6 +881,35 @@ find_invariant_insn (rtx insn, bool
>> always_reached, bool always_executed)
>> || HARD_REGISTER_P (dest))
>> simple = false;
>>
>> + /* Pre-check candidate to skip the one which can not make a valid insn
>> + during move_invariant_reg. */
>> + if (flag_ira_loop_pressure && df_live && simple
>> + && REG_P (dest) && DF_REG_DEF_COUNT (REGNO (dest)) > 1)
>
> Why only do this with (flag_ira_loop_pressure && df_live)? If the
> invariant can't be moved, we should ignore it regardless of whether
> register pressure is taken into account.
Thanks for the comments. df_live seams redundant.
With flag_ira_loop_pressure, the pass will call df_analyze () at the
beginning, which can make sure all the DF info are correct.
Can we guarantee all DF_... correct without df_analyze ()?
>> + {
>> + df_ref use;
>> + rtx ref;
>> + unsigned int i = REGNO (dest);
>> + struct df_insn_info *insn_info;
>> + df_ref *def_rec;
>> +
>> + for (use = DF_REG_USE_CHAIN (i); use; use = DF_REF_NEXT_REG (use))
>> + {
>> + ref = DF_REF_INSN (use);
>> + insn_info = DF_INSN_INFO_GET (ref);
>> +
>> + for (def_rec = DF_INSN_INFO_DEFS (insn_info); *def_rec; def_rec++)
>> + if (DF_REF_REGNO (*def_rec) == i)
>> + {
>> + /* Multi definitions at this stage, most likely are due to
>> + instruction constrain, which requires both read and write
>> + on the same register. Since move_invariant_reg is not
>> + powerful enough to handle such cases, just ignore the INV
>> + and leave the chance to others. */
>> + return;
>> + }
>> + }
>> + }
>> +
>> if (!may_assign_reg_p (SET_DEST (set))
>> || !check_maybe_invariant (SET_SRC (set)))
>> return;
>
>
> Can you put your new check between "may_assign_reg_p (dest)" and
> "check_maybe_invariant"? The may_assign_reg_p check is cheap and
> triggers quite often.
Updated and also removed the "flag_ira_loop_pressure && df_live". To
make it easy, I move the codes to a new function.
OK for trunk?
diff --git a/gcc/loop-invariant.c b/gcc/loop-invariant.c
index c6bf19b..d19f3c8 100644
--- a/gcc/loop-invariant.c
+++ b/gcc/loop-invariant.c
@@ -839,6 +852,39 @@ check_dependencies (rtx insn, bitmap depends_on)
return true;
}
+/* Pre-check candidate DEST to skip the one which can not make a valid insn
+ during move_invariant_reg. SIMPlE is to skip HARD_REGISTER. */
+static bool
+pre_check_invariant_p (bool simple, rtx dest)
+{
+ if (simple && REG_P (dest) && DF_REG_DEF_COUNT (REGNO (dest)) > 1)
+ {
+ df_ref use;
+ rtx ref;
+ unsigned int i = REGNO (dest);
+ struct df_insn_info *insn_info;
+ df_ref *def_rec;
+
+ for (use = DF_REG_USE_CHAIN (i); use; use = DF_REF_NEXT_REG (use))
+ {
+ ref = DF_REF_INSN (use);
+ insn_info = DF_INSN_INFO_GET (ref);
+
+ for (def_rec = DF_INSN_INFO_DEFS (insn_info); *def_rec; def_rec++)
+ if (DF_REF_REGNO (*def_rec) == i)
+ {
+ /* Multi definitions at this stage, most likely are due to
+ instruction constrain, which requires both read and write
+ on the same register. Since move_invariant_reg is not
+ powerful enough to handle such cases, just ignore the INV
+ and leave the chance to others. */
+ return false;
+ }
+ }
+ }
+ return true;
+}
+
/* Finds invariant in INSN. ALWAYS_REACHED is true if the insn is always
executed. ALWAYS_EXECUTED is true if the insn is always executed,
unless the program ends due to a function call. */
@@ -868,7 +914,8 @@ find_invariant_insn (rtx insn, bool
always_reached, bool always_executed)
|| HARD_REGISTER_P (dest))
simple = false;
- if (!may_assign_reg_p (SET_DEST (set))
+ if (!may_assign_reg_p (dest)
+ || !pre_check_invariant_p (simple, dest)
|| !check_maybe_invariant (SET_SRC (set)))
return;
