On November 13, 2015 5:26:01 PM GMT+01:00, Jeff Law <l...@redhat.com> wrote:
>On 11/13/2015 03:13 AM, Richard Biener wrote:
>
>>> diff --git a/gcc/Makefile.in b/gcc/Makefile.in
>>> index 34d2356..6613e83 100644
>>> --- a/gcc/Makefile.in
>>> +++ b/gcc/Makefile.in
>>> @@ -1474,6 +1474,7 @@ OBJS = \
>>> tree-ssa-loop.o \
>>> tree-ssa-math-opts.o \
>>> tree-ssa-operands.o \
>>> + tree-ssa-path-split.o \
>>
>> gimple-ssa-path-split please.
>Agreed. I'll make that change for Ajit.
>
>
>>
>>> tree-ssa-phionlycprop.o \
>>> tree-ssa-phiopt.o \
>>> tree-ssa-phiprop.o \
>>> diff --git a/gcc/common.opt b/gcc/common.opt
>>> index 757ce85..3e946ca 100644
>>> --- a/gcc/common.opt
>>> +++ b/gcc/common.opt
>>> @@ -2403,6 +2403,10 @@ ftree-vrp
>>> Common Report Var(flag_tree_vrp) Init(0) Optimization
>>> Perform Value Range Propagation on trees.
>>>
>>> +ftree-path-split
>>
>> fsplit-paths
>And this plus related variable name fixes and such.
>
>
>>>
>>> +@item -ftree-path-split
>>> +@opindex ftree-path-split
>>> +Perform Path Splitting on trees. When the two execution paths of a
>>> +if-then-else merge at the loop latch node, try to duplicate the
>>> +merge node into two paths. This is enabled by default at
>@option{-O2}
>>> +and above.
>>> +
>>
>> I think if we go into the detail of the transform we should mention
>the
>> effective result (creating a loop nest with disambiguation figuring
>out
>> which is the "better" inner loop).
>It no longer creates a loop nest. The overall shape of the CFG is
>maintained. ie, we still have a single simple latch for the loop. The
>
>blocks we create are internal to the loop.
>
>I always struggle with the right level at which to document these
>options. I'll take a look at this for Ajit.
>
>BTW Do we have an API for indicating that new blocks have been added to
>
>a loop? If so, then we can likely drop the LOOPS_NEED_FIXUP.
Please. It's called add_to_loop or so.
Richard.
>
>>
>>> @item -fsplit-ivs-in-unroller
>>> @opindex fsplit-ivs-in-unroller
>>> Enables expression of values of induction variables in later
>iterations
>>> diff --git a/gcc/opts.c b/gcc/opts.c
>>> index 9a3fbb3..9a0b27c 100644
>>> --- a/gcc/opts.c
>>> +++ b/gcc/opts.c
>>> @@ -509,6 +509,7 @@ static const struct default_options
>>> default_options_table[] =
>>> { OPT_LEVELS_2_PLUS, OPT_fisolate_erroneous_paths_dereference,
>NULL, 1
>>> },
>>> { OPT_LEVELS_2_PLUS, OPT_fipa_ra, NULL, 1 },
>>> { OPT_LEVELS_2_PLUS, OPT_flra_remat, NULL, 1 },
>>> + { OPT_LEVELS_2_PLUS, OPT_ftree_path_split, NULL, 1 },
>>
>> Is this transform a good idea for -Os?
>In general, no because of the block duplication.
>
>jeff
