[Patch, Fortran] CAF dep (3/3): coarrays - pass may_require_tmp informtion for CAF_get/send/sendget to the library

[Tobias Burnus]

This patch is based on 1/2 and 2/2 on the series. When the patch is 
approved, OpenCoarrays needs to be adapted; however, as surplus 
arguments of the callee are ignored, no immediate action is required. 
(And some delay avoids issues with compilers being older than the library.)

The issue comes up in the context of having a coarray access on the same 
image, e.g. "a[this_image()] = a", where alias questions play a role. 
While one can leave the general handling to the library - such as 
switching to memmove in case of local memory access, this patch tries to 
help the library to decide whether it has to create a temporary variable 
or not. For that reason, it passes an may_require_temporary argument to 
the library.

may_require_temporary is false if the source and target variables are 
disjunct, or if they are such overlapping that walking them in element 
order will not require a temporary (special case: identical). If the 
compiler cannot tell at compile time, the value is always one. Of 
course, if the memory access is for a different image than the current 
image (or for sendget: when the two image indexes are for different 
images), the library can ignore the argument "may_require_temporary" and 
use the normal remote memory access.

Build and regtested on x86-64-gnu-linux.
OK for the trunk?

Tobias

PS: I image code like the following in the library:

if (image_index == this_image)
   {
     if (contiguous LHS and RHS):
       use memmove
       // With special case: LHS and RHS identical
     if (!may_require_temporary)
       for-loop assigning
         LHS = RHS in element order
     else
       {
         tmp = malloc()
         if (RHS contiguous or scalar)
           tmp = memcpy(RHS)
         else
           for loop assigning RHS to tmp
         if (LHS contiguous)
           LHS = memcpy(tmp)
         else
           for loop assigning tmp to LHS
       }
   } else {
do normal remote-image assignment
   }
-------------- next part --------------
A non-text attachment was scrubbed...
Name: caf-dep.diff
Type: text/x-patch
Size: 25305 bytes
Desc: not available
URL: <http://gcc.gnu.org/pipermail/fortran/attachments/20140828/4e51697f/attachment.bin>