On Wed, Mar 9, 2016 at 6:54 PM, Alan Lawrence
<alan.lawre...@foss.arm.com> wrote:
> On 07/03/16 11:02, Alan Lawrence wrote:
>>
>> On 04/03/16 13:27, Richard Biener wrote:
>>>
>>> I think to make it work with LTO you need to mark it 'Optimization'.
>>> Also it's about
>>> arrays so maybe
>>>
>>> 'Assume common declarations may be overridden with ones with a larger
>>> trailing array'
>>>
>>> also if we document it here we should eventually document it in
>>> invoke.texi.
>>>
>>> Not sure if "unknown commons" is a good term, maybe "unconstrained
>>> commons" instead?
>>
>>
>> All done; I doubt there is really a good word, unconstrained seems as good
>> as
>> any. I've reused much the same wording in invoke.texi, unless you think
>> there
>> is more to add.
>>
>> On 04/03/16 13:33, Jakub Jelinek wrote:
>>>
>>> Also, isn't the *.opt description line supposed to end with a full stop?
>>
>>
>> Ah, yes, thanks.
>>
>> Is this version OK for trunk?
>>
>> gcc/ChangeLog:
>>
>> DATE Alan Lawrence <alan.lawre...@arm.com>
>> Jakub Jelinek <ja...@redhat.com>
>>
>> * common.opt (funconstrained-commons,
>> flag_unconstrained_commons): New.
>> * tree.c (array_at_struct_end_p): Do not limit to size of decl
>> for
>> DECL_COMMONS if flag_unconstrained_commons is set.
>> * tree-dfa.c (get_ref_base_and_extent): Likewise.
>
>
> And add to that
> * doc/invoke.texi (Optimize Options): Add -funconstrained-commons.
> (funconstrained-commons): Document.
Ok.
Richard.
> Thanks,
> Alan
>
>>
>> gcc/testsuite/ChangeLog:
>>
>> * gfortran.dg/unconstrained_commons.f: New.
>> ---
>> gcc/common.opt | 5 +++++
>> gcc/doc/invoke.texi | 8 +++++++-
>> gcc/testsuite/gfortran.dg/unconstrained_commons.f | 20
>> ++++++++++++++++++++
>> gcc/tree-dfa.c | 15 ++++++++++++++-
>> gcc/tree.c | 6 ++++--
>> 5 files changed, 50 insertions(+), 4 deletions(-)
>> create mode 100644 gcc/testsuite/gfortran.dg/unconstrained_commons.f
>>
>> diff --git a/gcc/common.opt b/gcc/common.opt
>> index 520fa9c..bbf79ef 100644
>> --- a/gcc/common.opt
>> +++ b/gcc/common.opt
>> @@ -2451,6 +2451,11 @@ fsplit-paths
>> Common Report Var(flag_split_paths) Init(0) Optimization
>> Split paths leading to loop backedges.
>>
>> +funconstrained-commons
>> +Common Var(flag_unconstrained_commons) Optimization
>> +Assume common declarations may be overridden with ones with a larger
>> +trailing array.
>> +
>> funit-at-a-time
>> Common Report Var(flag_unit_at_a_time) Init(1)
>> Compile whole compilation unit at a time.
>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
>> index 0a2a6f4..68933a1 100644
>> --- a/gcc/doc/invoke.texi
>> +++ b/gcc/doc/invoke.texi
>> @@ -407,7 +407,7 @@ Objective-C and Objective-C++ Dialects}.
>> -ftree-parallelize-loops=@var{n} -ftree-pre -ftree-partial-pre
>> -ftree-pta @gol
>> -ftree-reassoc -ftree-sink -ftree-slsr -ftree-sra @gol
>> -ftree-switch-conversion -ftree-tail-merge -ftree-ter @gol
>> --ftree-vectorize -ftree-vrp @gol
>> +-ftree-vectorize -ftree-vrp -funconstrained-commons @gol
>> -funit-at-a-time -funroll-all-loops -funroll-loops @gol
>> -funsafe-loop-optimizations -funsafe-math-optimizations -funswitch-loops
>> @gol
>> -fipa-ra -fvariable-expansion-in-unroller -fvect-cost-model -fvpt @gol
>> @@ -6659,6 +6659,12 @@ the loop optimizer itself cannot prove that these
>> assumptions are valid.
>> If you use @option{-Wunsafe-loop-optimizations}, the compiler warns you
>> if it finds this kind of loop.
>>
>> +@item -funconstrained-commons
>> +@opindex funconstrained-commons
>> +This option tells the compiler that variables declared in common blocks
>> +(e.g. Fortran) may later be overridden with longer trailing arrays. This
>> +prevents certain optimizations that depend on knowing the array bounds.
>> +
>> @item -fcrossjumping
>> @opindex fcrossjumping
>> Perform cross-jumping transformation.
>> diff --git a/gcc/testsuite/gfortran.dg/unconstrained_commons.f
>> b/gcc/testsuite/gfortran.dg/unconstrained_commons.f
>> new file mode 100644
>> index 0000000..f9fc471
>> --- /dev/null
>> +++ b/gcc/testsuite/gfortran.dg/unconstrained_commons.f
>> @@ -0,0 +1,20 @@
>> +! { dg-do compile }
>> +! { dg-options "-O3 -funconstrained-commons -fdump-tree-dom2-details" }
>> +
>> +! Test for PR69368: a single-element array in a common block, which will
>> be
>> +! overridden with a larger size at link time (contrary to language spec).
>> +! Dominator opts considers accesses to differently-computed elements of X
>> as
>> +! equivalent, unless -funconstrained-commons is passed in.
>> + SUBROUTINE FOO
>> + IMPLICIT DOUBLE PRECISION (X)
>> + INTEGER J
>> + COMMON /MYCOMMON / X(1)
>> + DO 10 J=1,1024
>> + X(J+1)=X(J+7)
>> + 10 CONTINUE
>> + RETURN
>> + END
>> +! { dg-final { scan-tree-dump-not "FIND" "dom2" } }
>> +! We should retain both a read and write of mycommon.x.
>> +! { dg-final { scan-tree-dump-times " _\[0-9\]+ =
>> mycommon\\.x\\\[_\[0-9\]+\\\];" 1 "dom2" } }
>> +! { dg-final { scan-tree-dump-times " mycommon\\.x\\\[_\[0-9\]+\\\] =
>> _\[0-9\]+;" 1 "dom2" } }
>> diff --git a/gcc/tree-dfa.c b/gcc/tree-dfa.c
>> index 0e98056..f133abc 100644
>> --- a/gcc/tree-dfa.c
>> +++ b/gcc/tree-dfa.c
>> @@ -612,9 +612,22 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT
>> *poffset,
>>
>> if (DECL_P (exp))
>> {
>> + if (flag_unconstrained_commons
>> + && TREE_CODE (exp) == VAR_DECL && DECL_COMMON (exp))
>> + {
>> + tree sz_tree = TYPE_SIZE (TREE_TYPE (exp));
>> + /* If size is unknown, or we have read to the end, assume there
>> + may be more to the structure than we are told. */
>> + if (TREE_CODE (TREE_TYPE (exp)) == ARRAY_TYPE
>> + || (seen_variable_array_ref
>> + && (sz_tree == NULL_TREE
>> + || TREE_CODE (sz_tree) != INTEGER_CST
>> + || (bit_offset + maxsize == wi::to_offset
>> (sz_tree)))))
>> + maxsize = -1;
>> + }
>> /* If maxsize is unknown adjust it according to the size of the
>> base decl. */
>> - if (maxsize == -1
>> + else if (maxsize == -1
>> && DECL_SIZE (exp)
>> && TREE_CODE (DECL_SIZE (exp)) == INTEGER_CST)
>> maxsize = wi::to_offset (DECL_SIZE (exp)) - bit_offset;
>> diff --git a/gcc/tree.c b/gcc/tree.c
>> index 07cb9d9..9179b37 100644
>> --- a/gcc/tree.c
>> +++ b/gcc/tree.c
>> @@ -12957,8 +12957,10 @@ array_at_struct_end_p (tree ref)
>> }
>>
>> /* If the reference is based on a declared entity, the size of the
>> array
>> - is constrained by its given domain. */
>> - if (DECL_P (ref))
>> + is constrained by its given domain. (Do not trust commons
>> PR/69368). */
>> + if (DECL_P (ref)
>> + && !(flag_unconstrained_commons
>> + && TREE_CODE (ref) == VAR_DECL && DECL_COMMON (ref)))
>> return false;
>>
>> return true;
>>
>
