[PATCH, ifcvt] Allow CC mode if HAVE_cbranchcc4 (fix s390 build)

[Zhenqiang Chen]

> -----Original Message-----
> From: Richard Henderson [mailto:rth@redhat.com]
> Sent: Thursday, November 06, 2014 4:23 PM
> To: Zhenqiang Chen; 'Jan-Benedict Glaw'; Hartmut Penner; Ulrich Weigand;
> Andreas Krebbel
> Cc: gcc-patches@gcc.gnu.org
> Subject: Re: [PATCH, ifcvt] Allow CC mode if HAVE_cbranchcc4 (fix s390
build)
> 
> On 11/06/2014 08:44 AM, Zhenqiang Chen wrote:
> > Hi,
> >
> > The patch add runtime check to fix s390 build fail
> > (https://gcc.gnu.org/ml/gcc-patches/2014-11/msg00050.html).
> >
> > And there is additional code to workaround s390 cstorecc4 issue.
> >
> > Bootstrap and no make check regression on X86-64.
> > Build s390-linux-gnu and s390x-linux-gnu.
> >
> > I do not have env to run full s390 tests. Would anyone in the TO list
> > help to run the s390 tests?
> >
> > Thanks!
> > -Zhenqiang
> >
> > ChangeLog:
> > 2014-11-06  Zhenqiang Chen  <zhenqiang.chen@arm.com>
> >
> > 	* ifcvt.c (noce_emit_cmove, noce_get_alt_condition,
> > noce_get_condition):
> > 	Allow CC mode if HAVE_cbranchcc4.
> > 	(noce_emit_store_flag): Change CC REG as cond_complex.
> >
> > diff --git a/gcc/ifcvt.c b/gcc/ifcvt.c index f4002f9..7f7b7c1 100644
> > --- a/gcc/ifcvt.c
> > +++ b/gcc/ifcvt.c
> > @@ -849,7 +849,10 @@ noce_emit_store_flag (struct noce_if_info
> > *if_info, rtx x, int reversep,
> >    enum rtx_code code;
> >
> >    cond_complex = (! general_operand (XEXP (cond, 0), VOIDmode)
> > -		  || ! general_operand (XEXP (cond, 1), VOIDmode));
> > +		  || ! general_operand (XEXP (cond, 1), VOIDmode)
> > +		     /* For s390, CC REG is general_operand.  But cstorecc4
> > only
> > +			handles CCZ1, which can not handle others like CCU.
> > */
> > +		  || GET_MODE_CLASS (GET_MODE (XEXP (cond, 0))) ==
> MODE_CC);
> >
> 
> I'd like to know more about this.  This seems like a mistake in the
backend.
> 
> > +#ifdef HAVE_cbranchcc4
> > +      if (GET_MODE_CLASS (GET_MODE (cmp_a)) != MODE_CC
> > +	  || cmp_b != const0_rtx
> > +	  || !(HAVE_cbranchcc4))
> > +#endif
> 
> Please add
> 
> #ifndef HAVE_cbranchcc4
> # define HAVE_cbranchcc4
> #endif
> 
> at the top of ifcvt.c along with all of the others.  Then use normal C
tests
> instead of preprocessor tests.

Thanks for the comment.
 
> > +  int allow_cc_mode = false;
> > +#ifdef HAVE_cbranchcc4
> > +  allow_cc_mode = HAVE_cbranchcc4;
> > +#endif
> 
> E.g. this becomes
> 
>   bool allow_cc_mode = HAVE_cbranchcc4;

After adding HAVE_cbranchcc4, we can just use HAVE_cbranchcc4. No need to
add a local variable allow_cc_mode.

Here is the updated patch.

diff --git a/gcc/ifcvt.c b/gcc/ifcvt.c
index f4002f9..21f08c2 100644
--- a/gcc/ifcvt.c
+++ b/gcc/ifcvt.c
@@ -75,6 +75,10 @@
    + 1)
 #endif
 
+#ifndef HAVE_cbranchcc4
+#define HAVE_cbranchcc4 0
+#endif
+
 #define IFCVT_MULTIPLE_DUMPS 1
 
 #define NULL_BLOCK	((basic_block) NULL)
@@ -1459,10 +1463,16 @@ noce_emit_cmove (struct noce_if_info *if_info, rtx
x, enum rtx_code code,
       end_sequence ();
     }
 
-  /* Don't even try if the comparison operands are weird.  */
+  /* Don't even try if the comparison operands are weird
+     except that the target supports cbranchcc4.  */
   if (! general_operand (cmp_a, GET_MODE (cmp_a))
       || ! general_operand (cmp_b, GET_MODE (cmp_b)))
-    return NULL_RTX;
+    {
+      if (!(HAVE_cbranchcc4)
+	  || GET_MODE_CLASS (GET_MODE (cmp_a)) != MODE_CC
+	  || cmp_b != const0_rtx)
+	return NULL_RTX;
+    }
 
 #if HAVE_conditional_move
   unsignedp = (code == LTU || code == GEU
@@ -1909,7 +1919,7 @@ noce_get_alt_condition (struct noce_if_info *if_info,
rtx target,
     }
 
   cond = canonicalize_condition (if_info->jump, cond, reverse,
-				 earliest, target, false, true);
+				 earliest, target, HAVE_cbranchcc4, true);
   if (! cond || ! reg_mentioned_p (target, cond))
     return NULL;
 
@@ -2401,7 +2411,7 @@ noce_get_condition (rtx_insn *jump, rtx_insn
**earliest, bool then_else_reversed
   /* Otherwise, fall back on canonicalize_condition to do the dirty
      work of manipulating MODE_CC values and COMPARE rtx codes.  */
   tmp = canonicalize_condition (jump, cond, reverse, earliest,
-				NULL_RTX, false, true);
+				NULL_RTX, HAVE_cbranchcc4, true);
 
   /* We don't handle side-effects in the condition, like handling
      REG_INC notes and making sure no duplicate conditions are emitted.  */