Adjust LSHIFT_EXPR handling of multiple_of_p

This removes the odd check of size_type_node when handling left-shifts
as multiplications of 1 << N and instead uses the type as specified.
It also moves left-shift handling next to multiplications where it
semantically belongs.

2022-01-24  Richard Biener  <rguenther@suse.de>

	* fold-const.cc (multiple_of_p): Re-write and move LSHIFT_EXPR
	handling.

diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index 8fc01cd..12732d3 100644 (file)
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -14079,7 +14079,7 @@ int
 multiple_of_p (tree type, const_tree top, const_tree bottom)
 {
   gimple *stmt;
-  tree t1, op1, op2;
+  tree op1, op2;
 
   if (operand_equal_p (top, bottom, 0))
     return 1;
@@ -14125,6 +14125,21 @@ multiple_of_p (tree type, const_tree top, const_tree bottom)
       return (multiple_of_p (type, TREE_OPERAND (top, 1), bottom)
              || multiple_of_p (type, TREE_OPERAND (top, 0), bottom));
 
+    case LSHIFT_EXPR:
+      /* Handle X << CST as X * (1 << CST) and only process the constant.  */
+      if (TREE_CODE (TREE_OPERAND (top, 1)) == INTEGER_CST)
+       {
+         op1 = TREE_OPERAND (top, 1);
+         if (wi::to_widest (op1) < TYPE_PRECISION (type))
+           {
+             wide_int mul_op
+               = wi::one (TYPE_PRECISION (type)) << wi::to_wide (op1);
+             return multiple_of_p (type,
+                                   wide_int_to_tree (type, mul_op), bottom);
+           }
+       }
+      return 0;
+
     case MINUS_EXPR:
       /* It is impossible to prove if op0 - op1 is multiple of bottom
         precisely, so be conservative here checking if both op0 and op1
@@ -14144,22 +14159,6 @@ multiple_of_p (tree type, const_tree top, const_tree bottom)
       return (multiple_of_p (type, op1, bottom)
              && multiple_of_p (type, TREE_OPERAND (top, 0), bottom));
 
-    case LSHIFT_EXPR:
-      if (TREE_CODE (TREE_OPERAND (top, 1)) == INTEGER_CST)
-       {
-         op1 = TREE_OPERAND (top, 1);
-         /* const_binop may not detect overflow correctly,
-            so check for it explicitly here.  */
-         if (wi::gtu_p (TYPE_PRECISION (TREE_TYPE (size_one_node)),
-                        wi::to_wide (op1))
-             && (t1 = fold_convert (type,
-                                    const_binop (LSHIFT_EXPR, size_one_node,
-                                                 op1))) != 0
-             && !TREE_OVERFLOW (t1))
-           return multiple_of_p (type, t1, bottom);
-       }
-      return 0;
-
     CASE_CONVERT:
       /* Can't handle conversions from non-integral or wider integral type.  */
       if ((TREE_CODE (TREE_TYPE (TREE_OPERAND (top, 0))) != INTEGER_TYPE)