[RFA] Rewrite data cache to use splay tree

[Jacob Potter <jdpotter at google dot com>]

Here's the first part of the dcache rewrite and stack caching changes
I've been working on. This patch re-implements the cache using a splay
tree, along with a linked list for an oldest-first replacement policy.
It also makes the cache write-through, rather than the old
partially-implemented writeback functionality.

I couldn't find a good place to store separate cache structures for
different inferiors; I think the answer is to just clear the cache
when current_target is changed, which I'll do in the second patch.

- Jacob

2009-07-07  Jacob Potter  <jdpotter@google.com>

        * dcache.c (ENTRY_INVALID, ENTRY_VALID, ENTRY_DIRTY): Delete.
        (state_chars): Delete.
        (struct dcache_block): Clean up; remove state and anydirty fields.
        (struct dcache_struct): Redefine as a splay tree and linked list.
        (dcache_writeback): Remove declaration.
        (dcache_invalidate, dcache_hit): Rewrite for new cache structure.
        (dcache_write_line): Delete.
        (dcache_read_line, dcache_alloc): Rewrite for new cache structure.
        (dcache_writeback): Delete.
        (dcache_peek_byte): Clean up; remove "invalid" state check.
        (dcache_poke_byte): Rewrite for new cache structure; clarify comment.
        (dcache_splay_tree_compare): New function.
        (dcache_init, dcache_free): Rewrite for new cache structure.
        (dcache_xfer_memory): Rewrite for new write-through cache structure.
        (dcache_update, dcache_print_line): New functions.
        (dcache_info): Rewrite for new cache structure.
        (_initialize_dcache): Rewrite for new cache structure.
        * dcache.h (dcache_xfer_memory): Update definition.
        (dcache_update, dcache_stack_enabled_p): Declare.
        * target.c (memory_xfer_partial): Update calls to dcache_xfer_memory.

Attachment: part1-dcache-rewrite.patch.txt
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