[pph] Fix checksum of trees coming from external PPH images (issue5554070)

[dnovillo at google dot com (Diego Novillo)]

When we read a tree from the cache of an external PPH file and the
tree is mutated in the current file, we need to re-sign the tree to
reflect the changes.

The problem was, that the signing code was assuming that the tree had
come from the *current* file, so it was trying to sign a cache entry
for the internal cache, which would ICE if the internal cache is
smaller than the external one.

I have not yet been able to produce a small test case for this, but it
fixes several thousand ICEs in our internal code.  I will add a test
case as soon as I get one reduced.



	* pph-in.c (pph_in_tree): Sign EXPR from the cache it was
	taken from.
	* pph-streamer.h (pph_cache_select): Handle PPH_RECORD_START,
	PPH_RECORD_START_MERGE_BODY, PPH_RECORD_START_MERGE_KEY
	and PPH_RECORD_START_MUTATED.

diff --git a/gcc/cp/pph-in.c b/gcc/cp/pph-in.c
index 2dbad83..0b2529f 100644
--- a/gcc/cp/pph-in.c
+++ b/gcc/cp/pph-in.c
@@ -2565,8 +2565,7 @@ pph_in_tree (pph_stream *stream)
       /* When reading a mutated tree, we only need to re-read its
          body, the tree itself is already in the cache for another
          PPH image.  */
-      expr = (tree) pph_cache_find (stream, PPH_RECORD_XREF, image_ix, ix,
-				    PPH_any_tree);
+      expr = (tree) pph_cache_find (stream, marker, image_ix, ix, PPH_any_tree);
     }
   else if (marker == PPH_RECORD_START_MERGE_BODY)
     {
@@ -2600,7 +2599,7 @@ pph_in_tree (pph_stream *stream)
     pph_trace_tree (expr, pph_trace_back,
 	marker == PPH_RECORD_START_MERGE_BODY ? pph_trace_merge_body
 	: marker == PPH_RECORD_START_MUTATED ? pph_trace_mutate
-	: pph_trace_normal );
+	: pph_trace_normal);
 
   /* If needed, sign the recently materialized tree to detect
      mutations.  Note that we only need to compute signatures
@@ -2612,8 +2611,13 @@ pph_in_tree (pph_stream *stream)
     {
       unsigned crc;
       size_t nbytes;
+      pph_cache *cache;
+
+      /* Retrieve the cache to sign based on where we materialized
+	 EXPR from.  */
+      cache = pph_cache_select (stream, marker, image_ix);
       crc = pph_get_signature (expr, &nbytes);
-      pph_cache_sign (&stream->cache, ix, crc, nbytes);
+      pph_cache_sign (cache, ix, crc, nbytes);
     }
 
   return expr;
diff --git a/gcc/cp/pph-streamer.h b/gcc/cp/pph-streamer.h
index b641776..c5db972 100644
--- a/gcc/cp/pph-streamer.h
+++ b/gcc/cp/pph-streamer.h
@@ -293,9 +293,16 @@ void pph_reader_finish (void);
 
 
 /* Return the pickle cache in STREAM corresponding to MARKER.
-   if MARKER is PPH_RECORD_IREF, it returns the cache in STREAM itself.
-   If MARKER is PPH_RECORD_XREF, it returns the cache in
-   STREAM->INCLUDES[INCLUDE_IX].
+   INCLUDE_IX is only used for MARKER values PPH_RECORD_XREF or
+   PPH_RECORD_START_MUTATED.
+
+   If MARKER is one of {PPH_RECORD_IREF, PPH_RECORD_START,
+   PPH_RECORD_START_MERGE_BODY, PPH_RECORD_START_MERGE_KEY}, it
+   returns the cache in STREAM itself.
+
+   If MARKER is one of {PPH_RECORD_XREF, PPH_RECORD_START_MUTATED}, it
+   returns the cache in STREAM->INCLUDES[INCLUDE_IX].
+
    If MARKER is a PREF, it returns the preloaded cache.  */
 static inline pph_cache *
 pph_cache_select (pph_stream *stream, enum pph_record_marker marker,
@@ -304,9 +311,13 @@ pph_cache_select (pph_stream *stream, enum pph_record_marker marker,
   switch (marker)
     {
     case PPH_RECORD_IREF:
+    case PPH_RECORD_START:
+    case PPH_RECORD_START_MERGE_BODY:
+    case PPH_RECORD_START_MERGE_KEY:
       return &stream->cache;
       break;
     case PPH_RECORD_XREF:
+    case PPH_RECORD_START_MUTATED:
       return &VEC_index (pph_stream_ptr, stream->includes, include_ix)->cache;
       break;
     case PPH_RECORD_PREF:

--
This patch is available for review at http://codereview.appspot.com/5554070