* [patch] Fix ICE during SCC hashing in LTO mode
@ 2015-06-30 10:21 Eric Botcazou
2015-06-30 11:11 ` Richard Biener
0 siblings, 1 reply; 5+ messages in thread
From: Eric Botcazou @ 2015-06-30 10:21 UTC (permalink / raw)
To: gcc-patches
[-- Attachment #1: Type: text/plain, Size: 1196 bytes --]
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 <ebotcazou@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 <ebotcazou@adacore.com>
* gnat.dg/lto17.ad[sb]: New test.
--
Eric Botcazou
[-- Attachment #2: p.diff --]
[-- Type: text/x-patch, Size: 3853 bytes --]
Index: 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,
[-- Attachment #3: lto17.adb --]
[-- Type: text/x-adasrc, Size: 251 bytes --]
-- { 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;
[-- Attachment #4: lto17.ads --]
[-- Type: text/x-adasrc, Size: 445 bytes --]
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;
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [patch] Fix ICE during SCC hashing in LTO mode
2015-06-30 10:21 [patch] Fix ICE during SCC hashing in LTO mode Eric Botcazou
@ 2015-06-30 11:11 ` Richard Biener
2015-06-30 21:17 ` Eric Botcazou
0 siblings, 1 reply; 5+ messages in thread
From: Richard Biener @ 2015-06-30 11:11 UTC (permalink / raw)
To: Eric Botcazou; +Cc: GCC Patches
On Tue, Jun 30, 2015 at 12:10 PM, Eric Botcazou <ebotcazou@adacore.com> wrote:
> 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?
Ok (I suppose this also affects the GCC 5 branch?)
Thanks,
Richard.
>
> 2015-06-30 Eric Botcazou <ebotcazou@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 <ebotcazou@adacore.com>
>
> * gnat.dg/lto17.ad[sb]: New test.
>
>
> --
> Eric Botcazou
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [patch] Fix ICE during SCC hashing in LTO mode
2015-06-30 11:11 ` Richard Biener
@ 2015-06-30 21:17 ` Eric Botcazou
2015-07-01 7:45 ` Richard Biener
0 siblings, 1 reply; 5+ messages in thread
From: Eric Botcazou @ 2015-06-30 21:17 UTC (permalink / raw)
To: Richard Biener; +Cc: gcc-patches
> Ok (I suppose this also affects the GCC 5 branch?)
Thanks. Yes, it does, but I'm not sure if we need to backport it immediately.
--
Eric Botcazou
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [patch] Fix ICE during SCC hashing in LTO mode
2015-06-30 21:17 ` Eric Botcazou
@ 2015-07-01 7:45 ` Richard Biener
2015-07-01 7:50 ` Eric Botcazou
0 siblings, 1 reply; 5+ messages in thread
From: Richard Biener @ 2015-07-01 7:45 UTC (permalink / raw)
To: Eric Botcazou; +Cc: GCC Patches
On Tue, Jun 30, 2015 at 11:03 PM, Eric Botcazou <ebotcazou@adacore.com> wrote:
>> Ok (I suppose this also affects the GCC 5 branch?)
>
> Thanks. Yes, it does, but I'm not sure if we need to backport it immediately.
Given there is no PR to track this I'll count on you remembering to
backport it then ;)
If you'd want it in 5.2 then you'd need to backport it by this Friday morning.
Richard.
> --
> Eric Botcazou
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [patch] Fix ICE during SCC hashing in LTO mode
2015-07-01 7:45 ` Richard Biener
@ 2015-07-01 7:50 ` Eric Botcazou
0 siblings, 0 replies; 5+ messages in thread
From: Eric Botcazou @ 2015-07-01 7:50 UTC (permalink / raw)
To: Richard Biener; +Cc: gcc-patches
> Given there is no PR to track this I'll count on you remembering to
> backport it then ;)
OK.
> If you'd want it in 5.2 then you'd need to backport it by this Friday
> morning.
No thanks. :-)
--
Eric Botcazou
^ permalink raw reply [flat|nested] 5+ messages in thread
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2015-06-30 10:21 [patch] Fix ICE during SCC hashing in LTO mode Eric Botcazou
2015-06-30 11:11 ` Richard Biener
2015-06-30 21:17 ` Eric Botcazou
2015-07-01 7:45 ` Richard Biener
2015-07-01 7:50 ` Eric Botcazou
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