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 --git a/gcc/ifcvt.cc b/gcc/ifcvt.cc
index 0858b3d2f6d6a646ee58b0a0f2de1b6c604371c0..60fc97a3907011bb1fb35e5d7d242cee6e5b2b9d 100644 (file)
--- 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;