[gcc r12-6939] Fix multiple_of_p behavior with NOP_EXPR

[gcc r12-6939] Fix multiple_of_p behavior with NOP_EXPR

[Richard Biener]

https://gcc.gnu.org/g:625f16c798757dcbfdded841f01d7c566d15c55c

commit r12-6939-g625f16c798757dcbfdded841f01d7c566d15c55c
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Jan 24 14:59:00 2022 +0100

    Fix multiple_of_p behavior with NOP_EXPR
    
    We were passing down the original type to recursive invocations
    of multiple_of_p for say (int)(unsigned * unsigned).
    
    2022-01-24  Richard Biener  <rguenther@suse.de>
    
            PR tree-optimization/100499
            * fold-const.cc (multiple_of_p): Pass the correct type of
            the expression to the recursive invocation of multiple_of_p
            for conversions and use CASE_CONVERT.

Diff:
---
 gcc/fold-const.cc | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index fd9c6352d4f..b155611578d 100644
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -14149,14 +14149,14 @@ multiple_of_p (tree type, const_tree top, const_tree bottom)
 	}
       return 0;
 
-    case NOP_EXPR:
+    CASE_CONVERT:
       /* Can't handle conversions from non-integral or wider integral type.  */
       if ((TREE_CODE (TREE_TYPE (TREE_OPERAND (top, 0))) != INTEGER_TYPE)
 	  || (TYPE_PRECISION (type)
 	      < TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (top, 0)))))
 	return 0;
-
-      /* fall through */
+      return multiple_of_p (TREE_TYPE (TREE_OPERAND (top, 0)),
+			    TREE_OPERAND (top, 0), bottom);
 
     case SAVE_EXPR:
       return multiple_of_p (type, TREE_OPERAND (top, 0), bottom);