Fix bswap optimization on big-endian (PR69714, 67781).

	PR tree-optimization/69714
	* tree-ssa-math-opts.c (find_bswap_or_nop): Revert previous change.
	Return NULL if we have irrelevant high bytes on BIG_ENDIAN.

testsuite/
	PR tree-optimization/69714
	* gcc.dg/torture/pr69714.c: New test.

From-SVN: r233452

1 files changed, 17 insertions, 29 deletions

diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c
index 3aa4a07..2215b4d 100644
--- a/gcc/tree-ssa-math-opts.c
+++ b/gcc/tree-ssa-math-opts.c
@@ -2449,11 +2449,9 @@ find_bswap_or_nop_1 (gimple *stmt, struct symbolic_number *n, int limit)
 static gimple *
 find_bswap_or_nop (gimple *stmt, struct symbolic_number *n, bool *bswap)
 {
-  unsigned rsize;
-  uint64_t tmpn, mask;
-/* The number which the find_bswap_or_nop_1 result should match in order
-   to have a full byte swap.  The number is shifted to the right
-   according to the size of the symbolic number before using it.  */
+  /* The number which the find_bswap_or_nop_1 result should match in order
+     to have a full byte swap.  The number is shifted to the right
+     according to the size of the symbolic number before using it.  */
   uint64_t cmpxchg = CMPXCHG;
   uint64_t cmpnop = CMPNOP;
 
@@ -2474,38 +2472,28 @@ find_bswap_or_nop (gimple *stmt, struct symbolic_number *n, bool *bswap)
 
   /* Find real size of result (highest non-zero byte).  */
   if (n->base_addr)
-    for (tmpn = n->n, rsize = 0; tmpn; tmpn >>= BITS_PER_MARKER, rsize++);
-  else
-    rsize = n->range;
+    {
+      unsigned HOST_WIDE_INT rsize;
+      uint64_t tmpn;
 
-  /* Zero out the bits corresponding to untouched bytes in original gimple
-     expression.  */
+      for (tmpn = n->n, rsize = 0; tmpn; tmpn >>= BITS_PER_MARKER, rsize++);
+      if (BYTES_BIG_ENDIAN && n->range != rsize)
+	/* This implies an offset, which is currently not handled by
+	   bswap_replace.  */
+	return NULL;
+      n->range = rsize;
+    }
+
+  /* Zero out the extra bits of N and CMP*.  */
   if (n->range < (int) sizeof (int64_t))
     {
+      uint64_t mask;
+
       mask = ((uint64_t) 1 << (n->range * BITS_PER_MARKER)) - 1;
       cmpxchg >>= (64 / BITS_PER_MARKER - n->range) * BITS_PER_MARKER;
       cmpnop &= mask;
     }
 
-  /* Zero out the bits corresponding to unused bytes in the result of the
-     gimple expression.  */
-  if (rsize < n->range)
-    {
-      if (BYTES_BIG_ENDIAN)
-	{
-	  mask = ((uint64_t) 1 << (rsize * BITS_PER_MARKER)) - 1;
-	  cmpxchg &= mask;
-	  cmpnop >>= (n->range - rsize) * BITS_PER_MARKER;
-	}
-      else
-	{
-	  mask = ((uint64_t) 1 << (rsize * BITS_PER_MARKER)) - 1;
-	  cmpxchg >>= (n->range - rsize) * BITS_PER_MARKER;
-	  cmpnop &= mask;
-	}
-      n->range = rsize;
-    }
-
   /* A complete byte swap should make the symbolic number to start with
      the largest digit in the highest order byte. Unchanged symbolic
      number indicates a read with same endianness as target architecture.  */