* module/language/cps/slot-allocation.scm (lookup-dead-slot-map)
(allocate-slots): For each non-tail call in a function, compute the
set of slots that are dead after the function has begun the call.
* module/language/cps/compile-bytecode.scm (compile-fun): Emit the
`dead-slot-map' macro instruction for non-tail calls.
* module/system/vm/assembler.scm (<asm>): Add `dead-slot-maps' member.
(dead-slot-map): New macro-instruction.
(link-frame-maps, link-dynamic-section, link-objects): Write dead
slots information into .guile.frame-maps sections of ELF files.
* module/system/vm/elf.scm (DT_GUILE_FRAME_MAPS): New definition.
* libguile/loader.h:
* libguile/loader.c (DT_GUILE_FRAME_MAPS, process_dynamic_segment):
(load_thunk_from_memory, register_elf): Arrange to parse
DT_GUILE_FRAME_MAPS out of the dynamic section.
(find_mapped_elf_image_unlocked, find_mapped_elf_image): New helpers.
(scm_find_mapped_elf_image): Refactor.
(scm_find_dead_slot_map_unlocked): New interface.
* libguile/vm.c (scm_i_vm_mark_stack): Mark the hottest frame
conservatively, as before. Otherwise use the dead slots map, if
available, to avoid marking data that isn't live.
* module/language/cps/compile-bytecode.scm (compile-fun): Now that all
$call expressions continue to $ktail or $ktrunc, remove the $kargs
case, and make receive-values bail if too many values are returned.
* module/language/cps.scm:
* module/language/cps/closure-conversion.scm:
* module/language/cps/compile-bytecode.scm:
* module/language/cps/dfg.scm:
* module/language/cps/slot-allocation.scm:
* module/language/cps/verify.scm:
* module/language/tree-il/compile-cps.scm: Remove "pop" member from
$prompt data type, as it is no longer used.
* module/language/cps/dfg.scm (constant-needs-allocation?): Use of a
constant in a $values expression of any arity does not cause slot
allocation.
* module/language/cps/compile-bytecode.scm (compile-fun): Allow $values
with a constant value to be compiled in test context. Really we
should fold these in a previous pass!
* module/language/cps/slot-allocation.scm (allocate-slots): Don't
allocate slots to unused results of function calls. This can allow us
to avoid consing a rest list for call-with-values with an ignored rest
parameter, and can improve the parallel move code.
* module/language/cps/compile-bytecode.scm (compile-fun): Adapt to avoid
emitting bind-rest in values context if the rest arg is unused.
