[gcc r16-7166] ifcvt: Improve noce_can_force_operand in ifcvt [PR122170]

[Andrew Pinski]

https://gcc.gnu.org/g:40f6ae016571ce6ea5951f406c4be7ff84914fbc

commit r16-7166-g40f6ae016571ce6ea5951f406c4be7ff84914fbc
Author: Andrew Pinski <andrew.pinski@oss.qualcomm.com>
Date:   Wed Jan 28 12:32:12 2026 -0800

    ifcvt: Improve noce_can_force_operand in ifcvt [PR122170]
    
    Currently if the rtl is either an arithmetic or an unary
    rtl, noce_can_force_operand checks to see if there is an
    optab for that rtl code. This works for more things except
    on some targets they have a ss_minus instruction but don't
    implement the optab for it. In the case of arm you can
    generate a ss_minus with a builtin and then when it comes
    to trying to do ifcvt, force_operand fails over.
    In this case the optab, sssub was only supported for
    fixed-point modes before and it was working as code_to_optab
    would return there was not optabs. But after r15-1030-gabe6d39365476e,
    the optab will be return. What the backend is doing is correct and will
    most likely happen with other rtl codes/optabs later on.
    
    To fix this instead of just returning true if the optab exists, we need
    to check if the optab entry for the mode exists.
    
            PR rtl-optimization/122170
    
    gcc/ChangeLog:
    
            * ifcvt.cc (noce_can_force_operand): Don't only check if
            there is an optab for the code check the entry for the
            mode is non-null. Handle non integral div by checking
            optab like force_operand does.
    
    Signed-off-by: Andrew Pinski <andrew.pinski@oss.qualcomm.com>

Diff:
---
 gcc/ifcvt.cc | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/gcc/ifcvt.cc b/gcc/ifcvt.cc
index 0858b3d2f6d6..60fc97a39070 100644
--- a/gcc/ifcvt.cc
+++ b/gcc/ifcvt.cc
@@ -919,13 +919,19 @@ noce_can_force_operand (rtx x)
       switch (GET_CODE (x))
 	{
 	case MULT:
-	case DIV:
 	case MOD:
 	case UDIV:
 	case UMOD:
 	  return true;
+	case DIV:
+	  if (INTEGRAL_MODE_P (GET_MODE (x)))
+	    return true;
+	  /* FALLTHRU */
 	default:
-	  return code_to_optab (GET_CODE (x));
+	  auto optab = code_to_optab (GET_CODE (x));
+	  if (!optab)
+	    return false;
+	  return optab_handler (optab, GET_MODE (x));
 	}
     }
   if (UNARY_P (x))
@@ -945,7 +951,10 @@ noce_can_force_operand (rtx x)
 	case UNSIGNED_FLOAT:
 	  return true;
 	default:
-	  return code_to_optab (GET_CODE (x));
+	  auto optab = code_to_optab (GET_CODE (x));
+	  if (!optab)
+	    return false;
+	  return optab_handler (optab, GET_MODE (x));
 	}
     }
   return false;