fold: Remove (rrotate (rrotate A CST) CST) folding [PR117492]

This removes an (broken) simplification from fold which is already handled in match.
The reason why it was broken is because of the use of wi::to_wide on the RHS of the
rotate which could be 2 different types even though the LHS was the same type.
Since it is already handled in match (by the patterns for
`Turn (a OP c1) OP c2 into a OP (c1+c2).`). It can be removed without losing any optimizations.

Bootstrapped and tested on x86_64-linux-gnu.

	PR middle-end/117492

gcc/ChangeLog:

	* fold-const.cc (fold_binary_loc): Remove `Two consecutive rotates adding up
	to the some integer` simplifcation.

gcc/testsuite/ChangeLog:

	* gcc.dg/torture/pr117492-1.c: New test.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>

diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index 0e374294c014137985d42baa9c43617d7c9d1e60..1e8ae1ab493ba8915a48fb95bd4e1487d3218a83 100644 (file)
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -12530,16 +12530,6 @@ fold_binary_loc (location_t loc, enum tree_code code, tree type,
                                                   arg01, arg1));
        }
 
-      /* Two consecutive rotates adding up to the some integer
-        multiple of the precision of the type can be ignored.  */
-      if (code == RROTATE_EXPR && TREE_CODE (arg1) == INTEGER_CST
-         && TREE_CODE (arg0) == RROTATE_EXPR
-         && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST
-         && wi::umod_trunc (wi::to_wide (arg1)
-                            + wi::to_wide (TREE_OPERAND (arg0, 1)),
-                            prec) == 0)
-       return fold_convert_loc (loc, type, TREE_OPERAND (arg0, 0));
-
       return NULL_TREE;
 
     case MIN_EXPR:

diff --git a/gcc/testsuite/gcc.dg/torture/pr117492-1.c b/gcc/testsuite/gcc.dg/torture/pr117492-1.c
new file mode 100644 (file)
index 0000000..543d8b7
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr117492-1.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* PR middle-end/117492 */
+
+/* This code would ICE in fold due to code which was using wi::to_wide with different types
+   and adding them. */
+
+typedef unsigned u;
+
+u
+foo(u x)
+{
+  return
+    __builtin_stdc_rotate_left((unsigned)
+      __builtin_stdc_rotate_right(x, 0x100000001ull),
+                                  1);
+}