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[Committed,loop2_invariant] Pre-check invariants

Message ID CACgzC7BXQGz_c1yQTXPUhdHmfpq+vNtEbKeaqJA3Sz15sH50jA@mail.gmail.com
State New
Headers show

Commit Message

Zhenqiang Chen June 23, 2014, 2:53 a.m. UTC 
On 18 June 2014 05:32, Jeff Law <law@redhat.com> wrote:
> On 06/11/14 03:35, Zhenqiang Chen wrote:
>>
>>
>> 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 ()?
>
> They should be fine in this context.
>
>
>
>> +/* 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.  */
>
> s/SIMPlE/SIMPLE/
>
>
>
>> +             {
>> +               /* Multi definitions at this stage, most likely are due to
>> +                  instruction constrain, which requires both read and
>> write
>
> s/constrain/constraints/
>
> Though that doesn't make sense.  Constraints don't come into play until much
> later in the pipeline.   Certainly there's been code in the expanders and
> elsewhere to try and make the code we generate more acceptable to 2-address
> targets and that's probably what you're really running into.   I think the
> code is fine, but that you need to improve the comment.
>
> ISTM that if your primary focus is to filter out read/write operands, then
> just say that and ignore the constraints or other mechanisms by which we got
> a read/write pseudo.
>
> So I think with those two small comment changes, this patch is OK for the
> trunk.  Please post the final version for archival purposes before checking
> it in.

Thanks. Patch was installed @r211885 with the two comment changes and
one more change to use

FOR_EACH_INSN_INFO_DEF

other than

for (def_rec = DF_INSN_INFO_DEFS (insn_info); *def_rec; def_rec++)

Bootstrap and no make check regression on X86-64.
diff mbox

Patch

Index: gcc/loop-invariant.c
===================================================================
--- gcc/loop-invariant.c        (revision 211832)
+++ gcc/loop-invariant.c        (working copy)
@@ -839,6 +839,39 @@ 
   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_EACH_INSN_INFO_DEF (def_rec, insn_info)
+           if (DF_REF_REGNO (def_rec) == i)
+             {
+               /* Multi definitions at this stage, most likely are due to
+                  instruction constraints, 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 +901,8 @@ 
       || 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;