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

[Thomas Preud'homme]

When analyzing a bitwise AND with a constant as part of a bitwise OR,
the bswap pass stores the constant in a int64_t variable without checking
if it fits. As a result, we get ICE when the constant is an __int128 value.
This affects GCC trunk but also GCC 4.9 and 4.8 (and possibly earlier
version as well).


ChangeLog are changed as follows:

*** gcc/ChangeLog ***

2014-06-05  Thomas Preud'homme  <thomas.preudho...@arm.com>

        PR tree-optimization/61375
        * tree-ssa-math-opts.c (init_symbolic_number): Cancel optimization if
        symbolic number cannot be represented in an unsigned HOST_WIDE_INT.
        (find_bswap_or_nop_1): Likewise.

*** gcc/testsuite/ChangeLog ***

2014-06-05  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..58df57a
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr61375.c
@@ -0,0 +1,34 @@
+#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 (PR210931).  */
+
+__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 658b341..95b3f25 100644
--- a/gcc/tree-ssa-math-opts.c
+++ b/gcc/tree-ssa-math-opts.c
@@ -1717,6 +1717,8 @@ init_symbolic_number (struct symbolic_number *n, tree src)
   if (n->size % BITS_PER_UNIT != 0)
     return false;
   n->size /= BITS_PER_UNIT;
+  if (n->size > (int)sizeof (unsigned HOST_WIDE_INT))
+    return false;
   n->range = n->size;
   n->n = CMPNOP;
 
@@ -1883,6 +1885,8 @@ find_bswap_or_nop_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)sizeof (unsigned HOST_WIDE_INT) * 8)
+             return NULL_TREE;
 
            if (type_size / BITS_PER_UNIT < (int)(sizeof (int64_t)))
              {

Is this OK for trunk? What about backports for 4.8 and 4.9? Would a
reworked patch for these versions be accepted? The change would
be trivial: the code in init_symbolic_number now was moved from
some other place.

Best regards,

Thomas