Re: debug-early branch merged into mainline

[Aldy Hernandez <aldyh@redhat.com>]

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On 06/07/2015 02:33 PM, Richard Biener wrote:
> On June 7, 2015 6:00:05 PM GMT+02:00, Aldy Hernandez <aldyh@redhat.com> wrote:
>> On 06/07/2015 11:25 AM, Richard Biener wrote:
>>> On June 7, 2015 5:03:30 PM GMT+02:00, Aldy Hernandez
>> <aldyh@redhat.com> wrote:
>>>> On 06/06/2015 05:49 AM, Andreas Schwab wrote:
>>>>> Bootstrap fails on aarch64:
>>>>>
>>>>> Comparing stages 2 and 3
>>>>> warning: gcc/cc1objplus-checksum.o differs
>>>>> warning: gcc/cc1obj-checksum.o differs
>>>>> warning: gcc/cc1plus-checksum.o differs
>>>>> warning: gcc/cc1-checksum.o differs
>>>>> Bootstrap comparison failure!
>>>>> gcc/ira-costs.o differs
>>>>> gcc/tree-sra.o differs
>>>>> gcc/tree-parloops.o differs
>>>>> gcc/tree-vect-data-refs.o differs
>>>>> gcc/java/jcf-io.o differs
>>>>> gcc/ipa-inline-analysis.o differs
>>>>
>>>> The bootstrap comparison failure on ppc64le, aarch64, and possibly
>>>> others is due to the order of some sections being in a different
>> order
>>>> with and without debugging.
>>>>
>>>> Stage2 is being compiled with no debugging due to -gtoggle, and
>> stage3
>>>> is being compiled with debugging.
>>>>
>>>> For ira-costs.o on ppc64le we have:
>>>>
>>>> -Disassembly of section
>>>>
>> .rodata._ZN10hash_tableI19cost_classes_hasher11xcallocatorE6expandEv.str1.8:
>>>> +Disassembly of section
>>>>
>> .rodata._ZN10hash_tableI19cost_classes_hasher11xcallocatorE26find_empty_slot_for_expandEj.str1.8:
>>>>
>>>> ...
>>>>
>>>> -Disassembly of section
>>>>
>> .rodata._ZN10hash_tableI19cost_classes_hasher11xcallocatorE26find_empty_slot_for_expandEj.str1.8:
>>>> +Disassembly of section
>>>>
>> .rodata._ZN10hash_tableI19cost_classes_hasher11xcallocatorE6expandEv.str1.8:
>>>>
>>>> There is no semantic difference between the objects, just the
>> ordering.
>>>>
>>>> I assume it's the same problem for the rest of the objects and
>>>> architectures.
>>>>
>>>> I will look into this, unless someone beats me to it, or has an idea
>>>> right off the bat.
>>>
>>> Check whether the symbol table walkers are walking hash tables.  I
>> assume the above are emitted via the symbol removal handling for debug
>> stuff?
>>
>> Ughh, indeed.  These sections are being outputted from
>> output_object_blocks which traverses a hash table:
>>
>> void
>> output_object_blocks (void)
>> {
>>   object_block_htab->traverse<void *, output_object_block_htab> (NULL);
>> }
>>
>> Perhaps we should sort them by some deterministic field and then call
>> output_object_block() on each member of the resulting list?
>
> Yes, that would be the usual fix. Maybe sth has an UID already, is the 'object' a decl by chance?

The attached patch fixes the bootstrap failure on ppc64le, and 
theoretically the aarch64 problem as well, but I haven't checked.

Tested on ppc64le linux by bootstrapping, and regtesting C/C++ against 
pre debug-early merge sources.  Also tested by a full bootstrap and 
regtest on x86-64 Linux.

OK for mainline?

Aldy

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	* varasm.c (output_object_block_htab): Push each object_block into
	a vector instead of calling output_object_block.
	(output_object_block_compare): New.
	(output_object_blocks): Sort object_blocks and then output them.

diff --git a/gcc/varasm.c b/gcc/varasm.c
index 18f3eac..008360e 100644
--- a/gcc/varasm.c
+++ b/gcc/varasm.c
@@ -7420,22 +7420,57 @@ output_object_block (struct object_block *block)
     }
 }
 
-/* A htab_traverse callback used to call output_object_block for
-   each member of object_block_htab.  */
+/* An htab_traverse callback used to copy object_blocks into a vector.  */
 
 int
-output_object_block_htab (object_block **slot, void *)
+output_object_block_htab (object_block **slot, void *data)
 {
-  output_object_block (*slot);
+  vec<object_block *, va_heap> *v = (vec<object_block *, va_heap> *) data;
+  v->safe_push (*slot);
   return 1;
 }
 
+/* A callback for qsort to compare object_blocks.  We only care about
+   named sections.  */
+
+static int
+output_object_block_compare (const void *x, const void *y)
+{
+  object_block *p1 = *(object_block * const*)x;
+  object_block *p2 = *(object_block * const*)y;
+
+  if (p1->sect->common.flags & SECTION_NAMED
+      && !(p2->sect->common.flags & SECTION_NAMED))
+    return 1;
+
+  if (!(p1->sect->common.flags & SECTION_NAMED)
+      && p2->sect->common.flags & SECTION_NAMED)
+    return -1;
+
+  if (p1->sect->common.flags & SECTION_NAMED
+      && p2->sect->common.flags & SECTION_NAMED)
+    return strcmp (p1->sect->named.name,
+		   p2->sect->named.name);
+
+  return 0;
+}
+
 /* Output the definitions of all object_blocks.  */
 
 void
 output_object_blocks (void)
 {
-  object_block_htab->traverse<void *, output_object_block_htab> (NULL);
+  vec<object_block *, va_heap> v = vNULL;
+  object_block_htab->traverse<void *, output_object_block_htab> (&v);
+
+  /* Sort them in order to output them in a deterministic manner,
+     otherwise we may get .rodata sections in different orders with
+     and without -g.  */
+  v.qsort (output_object_block_compare);
+  unsigned i;
+  object_block *obj;
+  FOR_EACH_VEC_ELT (v, i, obj)
+    output_object_block (obj);
 }
 
 /* This function provides a possible implementation of the