http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54779
Bug #: 54779
Summary: split FRAME variables back into pieces
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: middle-end
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: ebotca...@gcc.gnu.org
CC: jamb...@gcc.gnu.org
Created attachment 28323
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28323
Original implementation
When nested functions access local variables of their parent, the compiler
creates a special FRAME local variable in the parent, which represents the
non-local frame, and puts into it all the variables accessed non-locally.
If these nested functions are later inlined into their parent, these FRAME
variables generally remain unmodified and this has various drawbacks:
1) the frame of the parent is unnecessarily large,
2) scalarization of aggregates put into the FRAME variables is hindered,
3) debug info for scalars put into the FRAME variables is poor since VTA only
works on GIMPLE registers.
The attached patch makes it so that the compiler splits FRAME variables back
into pieces when all the nested functions have been inlined. The
transformation
is implemented as a sub-pass of execute_update_addresses_taken. It also comes
with a testcase. Prerequisite is revision 191970.
* gimple.c (gimple_ior_addresses_taken_1): Handle non-local frame
structures specially.
* tree-ssa.c (lookup_decl_for_field): New static function.
(split_nonlocal_frames_op): Likewise.
(execute_update_addresses_taken): Break up non-local frame structures
into variables when possible.
