[gcc r12-7420] arc: Fix for new ifcvt behavior [PR104154]

[gcc r12-7420] arc: Fix for new ifcvt behavior [PR104154]

[Robin Dapp]

https://gcc.gnu.org/g:2240ebd8e46e098f972a662d0aad85348b304889

commit r12-7420-g2240ebd8e46e098f972a662d0aad85348b304889
Author: Robin Dapp <rdapp@linux.ibm.com>
Date:   Mon Feb 7 08:39:41 2022 +0100

    arc: Fix for new ifcvt behavior [PR104154]
    
    ifcvt now passes a CC-mode "comparison" to backends.  This patch
    simply returns from gen_compare_reg () in that case since nothing
    needs to be prepared anymore.
    
    gcc/ChangeLog:
    
            PR rtl-optimization/104154
            * config/arc/arc.cc (gen_compare_reg):  Return the CC-mode
            comparison ifcvt passed us.

Diff:
---
 gcc/config/arc/arc.cc | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/gcc/config/arc/arc.cc b/gcc/config/arc/arc.cc
index c27ba99eb60..fbc17e684a0 100644
--- a/gcc/config/arc/arc.cc
+++ b/gcc/config/arc/arc.cc
@@ -2256,6 +2256,12 @@ gen_compare_reg (rtx comparison, machine_mode omode)
   cmode = GET_MODE (x);
   if (cmode == VOIDmode)
     cmode = GET_MODE (y);
+
+  /* If ifcvt passed us a MODE_CC comparison we can
+     just return it.  It should be in the proper form already.   */
+  if (GET_MODE_CLASS (cmode) == MODE_CC)
+    return comparison;
+
   if (cmode != SImode && cmode != SFmode && cmode != DFmode)
     return NULL_RTX;
   if (cmode == SImode)