RE: [PATCH] Fix PR61375: cancel bswap optimization when value doesn't fit in a HOST_WIDE_INT

[Thomas Preud'homme]

Ok, what about the following patch and associated ChangeLog entries?

2014-06-24  Thomas Preud'homme  <thomas.preudho...@arm.com>

        PR tree-optimization/61375
        * tree-ssa-math-opts.c (find_bswap_or_nop_1): Cancel optimization if
        symbolic number cannot be represented in an unsigned HOST_WIDE_INT.
        (execute_optimize_bswap): Cancel optimization if CHAR_BIT != 8.

2014-06-24  Thomas Preud'homme  <thomas.preudho...@arm.com>

        PR tree-optimization/61375
        * gcc.c-torture/execute/pr61375-1.c: New test.


diff --git a/gcc/testsuite/gcc.c-torture/execute/pr61375.c 
b/gcc/testsuite/gcc.c-torture/execute/pr61375.c
new file mode 100644
index 0000000..6fb4693
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr61375.c
@@ -0,0 +1,35 @@
+#ifdef __UINT64_TYPE__
+typedef __UINT64_TYPE__ uint64_t;
+#else
+typedef unsigned long long uint64_t;
+#endif
+
+#ifndef __SIZEOF_INT128__
+#define __int128 long long
+#endif
+
+/* Some version of bswap optimization would ICE when analyzing a mask constant
+   too big for an HOST_WIDE_INT (PR61375).  */
+
+__attribute__ ((noinline, noclone)) uint64_t
+uint128_central_bitsi_ior (unsigned __int128 in1, uint64_t in2)
+{
+  __int128 mask = (__int128)0xffff << 56;
+  return ((in1 & mask) >> 56) | in2;
+}
+
+int
+main (int argc)
+{
+  __int128 in = 1;
+#ifdef __SIZEOF_INT128__
+  in <<= 64;
+#endif
+  if (sizeof (uint64_t) * __CHAR_BIT__ != 64)
+    return 0;
+  if (sizeof (unsigned __int128) * __CHAR_BIT__ != 128)
+    return 0;
+  if (uint128_central_bitsi_ior (in, 2) != 0x102)
+    __builtin_abort ();
+  return 0;
+}
diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c
index 9ff857c..045bf48 100644
--- a/gcc/tree-ssa-math-opts.c
+++ b/gcc/tree-ssa-math-opts.c
@@ -1740,6 +1740,8 @@ find_bswap_1 (gimple stmt, struct symbolic_number *n, int 
limit)
          n->size = TYPE_PRECISION (TREE_TYPE (rhs1));
          if (n->size % BITS_PER_UNIT != 0)
            return NULL_TREE;
+         if (n->size > HOST_BITS_PER_WIDEST_INT)
+           return NULL_TREE;
          n->size /= BITS_PER_UNIT;
          n->n = (sizeof (HOST_WIDEST_INT) < 8 ? 0 :
                  (unsigned HOST_WIDEST_INT)0x08070605 << 32 | 0x04030201);
@@ -1781,6 +1783,8 @@ find_bswap_1 (gimple stmt, struct symbolic_number *n, int 
limit)
            type_size = TYPE_PRECISION (gimple_expr_type (stmt));
            if (type_size % BITS_PER_UNIT != 0)
              return NULL_TREE;
+           if (type_size > (int) HOST_BITS_PER_WIDEST_INT)
+             return NULL_TREE;
 
            if (type_size / BITS_PER_UNIT < (int)(sizeof (HOST_WIDEST_INT)))
              {
@@ -1911,7 +1915,7 @@ execute_optimize_bswap (void)
   bool changed = false;
   tree bswap16_type = NULL_TREE, bswap32_type = NULL_TREE, bswap64_type = 
NULL_TREE;
 
-  if (BITS_PER_UNIT != 8)
+  if (BITS_PER_UNIT != 8 || CHAR_BIT != 8)
     return 0;
 
   if (sizeof (HOST_WIDEST_INT) < 8)

Is this ok for 4.8 and 4.9 branches?

Best regards,

Thomas