bswap: Handle bswapping of pointers [PR96573]

In GCC8/9 we used to optimize this into a bswap, but we no longer do.
Handling byteswapping of pointers is easy, all we need is to allow them,
for the __builtin_bswap* we already use TYPE_PRECISION to determine
the precision and we cast the operand and result to the correct type
if they aren't uselessly convertible to what the builtin expects.

2021-04-01  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/96573
	* gimple-ssa-store-merging.c (init_symbolic_number): Handle
	also pointer types.

	* gcc.dg/pr96573.c: New test.

diff --git a/gcc/gimple-ssa-store-merging.c b/gcc/gimple-ssa-store-merging.c
index 213c155..30bd663 100644 (file)
--- a/gcc/gimple-ssa-store-merging.c
+++ b/gcc/gimple-ssa-store-merging.c
@@ -333,7 +333,7 @@ init_symbolic_number (struct symbolic_number *n, tree src)
 {
   int size;
 
-  if (! INTEGRAL_TYPE_P (TREE_TYPE (src)))
+  if (!INTEGRAL_TYPE_P (TREE_TYPE (src)) && !POINTER_TYPE_P (TREE_TYPE (src)))
     return false;
 
   n->base_addr = n->offset = n->alias_set = n->vuse = NULL_TREE;

diff --git a/gcc/testsuite/gcc.dg/pr96573.c b/gcc/testsuite/gcc.dg/pr96573.c
new file mode 100644 (file)
index 0000000..3acf117
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr96573.c
@@ -0,0 +1,20 @@
+/* PR tree-optimization/96573 */
+/* { dg-do compile { target { lp64 || ilp32 } } } */
+/* { dg-require-effective-target bswap } */
+/* { dg-options "-O3 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump "__builtin_bswap" "optimized" } } */
+
+typedef __SIZE_TYPE__ size_t;
+
+void *
+foo (void * const p)
+{
+  const size_t m = sizeof (p) - 1;
+  const unsigned char * const o = (unsigned char*) &p;
+  void *n;
+  unsigned char * const q = (unsigned char *) &n;
+  unsigned char i;
+  for (i = 0; i <= m; ++i)
+    q[m - i] = o[i];
+  return n;
+}