tree-optimization/107617 - big-endian .LEN_STORE VN

The following fixes a mistake in interpreting .LEN_STORE definitions
during value-numbering when in big-endian mode.  We cannot offset
the encoding of the RHS but instead encode to an offsetted position
which is then treated correctly by the endian aware copying code.

	PR tree-optimization/107617
	* tree-ssa-sccvn.cc (vn_walk_cb_data::push_partial_def):
	Handle negative pd.rhs_off.
	(vn_reference_lookup_3): Properly provide pd.rhs_off
	for .LEN_STORE on big-endian targets.

diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc
index b9f289b..fa2f65d 100644 (file)
--- a/gcc/tree-ssa-sccvn.cc
+++ b/gcc/tree-ssa-sccvn.cc
@@ -2090,7 +2090,7 @@ vn_walk_cb_data::push_partial_def (pd_data pd,
            len = ROUND_UP (pd.size, BITS_PER_UNIT) / BITS_PER_UNIT;
          memset (this_buffer, 0, len);
        }
-      else
+      else if (pd.rhs_off >= 0)
        {
          len = native_encode_expr (pd.rhs, this_buffer, bufsize,
                                    (MAX (0, -pd.offset)
@@ -2105,6 +2105,24 @@ vn_walk_cb_data::push_partial_def (pd_data pd,
              return (void *)-1;
            }
        }
+      else /* negative pd.rhs_off indicates we want to chop off first bits */
+       {
+         if (-pd.rhs_off >= bufsize)
+           return (void *)-1;
+         len = native_encode_expr (pd.rhs,
+                                   this_buffer + -pd.rhs_off / BITS_PER_UNIT,
+                                   bufsize - -pd.rhs_off / BITS_PER_UNIT,
+                                   MAX (0, -pd.offset) / BITS_PER_UNIT);
+         if (len <= 0
+             || len < (ROUND_UP (pd.size, BITS_PER_UNIT) / BITS_PER_UNIT
+                       - MAX (0, -pd.offset) / BITS_PER_UNIT))
+           {
+             if (dump_file && (dump_flags & TDF_DETAILS))
+               fprintf (dump_file, "Failed to encode %u "
+                        "partial definitions\n", ndefs);
+             return (void *)-1;
+           }
+       }
 
       unsigned char *p = buffer;
       HOST_WIDE_INT size = pd.size;
@@ -3349,10 +3367,13 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_,
                }
              else if (fn == IFN_LEN_STORE)
                {
-                 pd.rhs_off = 0;
                  pd.offset = offset2i;
                  pd.size = (tree_to_uhwi (len)
                             + -tree_to_shwi (bias)) * BITS_PER_UNIT;
+                 if (BYTES_BIG_ENDIAN)
+                   pd.rhs_off = pd.size - tree_to_uhwi (TYPE_SIZE (vectype));
+                 else
+                   pd.rhs_off = 0;
                  if (ranges_known_overlap_p (offset, maxsize,
                                              pd.offset, pd.size))
                    return data->push_partial_def (pd, set, set,