Hi,
the attached Ada testcase triggers an internal error in LTO mode:
eric@polaris:~/build/gcc/native> gcc/gnat1 -quiet lto17.adb -flto
+===========================GNAT BUG DETECTED==============================+
| 6.0.0 20150629 (experimental) [trunk revision 225111] (x86_64-suse-linux)
GCC error:|
| in hash_scc, at lto-streamer-out.c:1445
This is the assertion verifying that you walk the same SCC using DFS after
starting from another element of the SCC in hash_scc. It fails here because
this second DFS is not performed with the same THIS_REF_P parameter as the
initial one, so there is no guaranteee that this will yield the same result
because DFS_write_tree will behave differently.
Fixed by passing the THIS_REF_P and REF_P parameters for FIRST to hash_scc.
Tested on x86_64-suse-linux, OK for the mainline?
2015-06-30 Eric Botcazou <ebotca...@adacore.com>
* lto-streamer-out.c (class DFS): Adjust hash_scc method.
(DFS::DFS): Pass this_ref_p and ref_p to hash_scc.
(hash_scc): Add this_ref_p and ref_p parameters and pass them
to the inner DFS walk.
2015-06-30 Eric Botcazou <ebotca...@adacore.com>
* gnat.dg/lto17.ad[sb]: New test.
--
Eric BotcazouIndex: lto-streamer-out.c
===================================================================
--- lto-streamer-out.c (revision 225111)
+++ lto-streamer-out.c (working copy)
@@ -411,9 +411,9 @@ lto_write_tree (struct output_block *ob,
streamer_write_zero (ob);
}
-/* Emit the physical representation of tree node EXPR to output block
- OB. If THIS_REF_P is true, the leaves of EXPR are emitted as references
- via lto_output_tree_ref. REF_P is used for streaming siblings of EXPR. */
+/* Emit the physical representation of tree node EXPR to output block OB,
+ If THIS_REF_P is true, the leaves of EXPR are emitted as references via
+ lto_output_tree_ref. REF_P is used for streaming siblings of EXPR. */
static void
lto_output_tree_1 (struct output_block *ob, tree expr, hashval_t hash,
@@ -490,13 +490,20 @@ private:
tree expr, bool ref_p, bool this_ref_p);
hashval_t
- hash_scc (struct output_block *ob, unsigned first, unsigned size);
+ hash_scc (struct output_block *ob, unsigned first, unsigned size,
+ bool ref_p, bool this_ref_p);
hash_map<tree, sccs *> sccstate;
vec<worklist> worklist_vec;
struct obstack sccstate_obstack;
};
+/* Emit the physical representation of tree node EXPR to output block OB,
+ using depth-first search on the subgraph. If THIS_REF_P is true, the
+ leaves of EXPR are emitted as references via lto_output_tree_ref.
+ REF_P is used for streaming siblings of EXPR. If SINGLE_P is true,
+ this is for a rewalk of a single leaf SCC. */
+
DFS::DFS (struct output_block *ob, tree expr, bool ref_p, bool this_ref_p,
bool single_p)
{
@@ -564,7 +571,7 @@ DFS::DFS (struct output_block *ob, tree
unsigned first, size;
tree x;
- /* If we are re-walking a single leaf-SCC just pop it,
+ /* If we are re-walking a single leaf SCC just pop it,
let earlier worklist item access the sccstack. */
if (single_p)
{
@@ -587,7 +594,7 @@ DFS::DFS (struct output_block *ob, tree
unsigned scc_entry_len = 0;
if (!flag_wpa)
{
- scc_hash = hash_scc (ob, first, size);
+ scc_hash = hash_scc (ob, first, size, ref_p, this_ref_p);
/* Put the entries with the least number of collisions first. */
unsigned entry_start = 0;
@@ -1362,10 +1369,12 @@ DFS::scc_entry_compare (const void *p1_,
return 0;
}
-/* Return a hash value for the SCC on the SCC stack from FIRST with SIZE. */
+/* Return a hash value for the SCC on the SCC stack from FIRST with SIZE.
+ THIS_REF_P and REF_P are as passed to lto_output_tree for FIRST. */
hashval_t
-DFS::hash_scc (struct output_block *ob, unsigned first, unsigned size)
+DFS::hash_scc (struct output_block *ob, unsigned first, unsigned size,
+ bool ref_p, bool this_ref_p)
{
unsigned int last_classes = 0, iterations = 0;
@@ -1441,7 +1450,8 @@ DFS::hash_scc (struct output_block *ob,
for (unsigned i = 0; i < size; ++i)
map.put (sccstack[first+i].t, sccstack[first+i].hash);
- DFS again (ob, sccstack[first+firstunique].t, false, false, true);
+ DFS again (ob, sccstack[first+firstunique].t, ref_p, this_ref_p,
+ true);
gcc_assert (again.sccstack.length () == size);
memcpy (sccstack.address () + first,
@@ -1539,9 +1549,9 @@ DFS::DFS_write_tree (struct output_block
}
-/* Emit the physical representation of tree node EXPR to output block
- OB. If THIS_REF_P is true, the leaves of EXPR are emitted as references
- via lto_output_tree_ref. REF_P is used for streaming siblings of EXPR. */
+/* Emit the physical representation of tree node EXPR to output block OB.
+ If THIS_REF_P is true, the leaves of EXPR are emitted as references via
+ lto_output_tree_ref. REF_P is used for streaming siblings of EXPR. */
void
lto_output_tree (struct output_block *ob, tree expr,-- { dg-do compile }
-- { dg-options "-flto" }
-- { dg-require-effective-target lto }
package body Lto17 is
function To_Chunk_List(C : Chunk) return Chunk_List is
begin
return new Chunk_List_Element'(C.Size, C, null);
end;
end Lto17;package Lto17 is
type Chunk_List_Element;
type Chunk_List is access Chunk_List_Element;
type Arr is array (Natural range <>) of Integer;
type Chunk(Size : Natural) is record
Data : Arr(1 .. Size);
Where : Natural;
end record;
type Chunk_List_Element(Size : Natural) is record
Chnk : Chunk(Size);
Link : Chunk_List;
end record;
function To_Chunk_List(C : Chunk) return Chunk_List;
end Lto17;
