On Tue, 2009-08-18 at 21:21 +0200, Tomek Grabiec wrote:
> Like I said on IRC, this will not work for empty basic blocks, because
> spill_at_insn will belong to the preceding
> basic block. This causes that instructions will be added to different
> (preceding) basic block and might not be executed on some
> execution paths.
I think the following patch _is_ correct but it breaks "make regression"
so I think we're silently spilling/reloading empty basic blocks.
Pekka
>From 999622798d073ae892c316e6f69fde7697233e4d Mon Sep 17 00:00:00 2001
From: Pekka Enberg <penb...@cs.helsinki.fi>
Date: Tue, 18 Aug 2009 21:12:22 +0300
Subject: [PATCH] spill-reload: Use radix_tree_lookup() in bb_last_insn()
Lets use radix_tree_lookup() and get rid of the nasty loop in
bb_last_insn().
Cc: Arthur HUILLET <arthur.huil...@free.fr>
Cc: Tomek Grabiec <tgrab...@gmail.com>
Signed-off-by: Pekka Enberg <penb...@cs.helsinki.fi>
---
include/jit/basic-block.h | 5 +++++
jit/basic-block.c | 23 ++++++++---------------
jit/spill-reload.c | 3 ++-
3 files changed, 15 insertions(+), 16 deletions(-)
diff --git a/include/jit/basic-block.h b/include/jit/basic-block.h
index e50f6c6..e1d8c86 100644
--- a/include/jit/basic-block.h
+++ b/include/jit/basic-block.h
@@ -74,6 +74,11 @@ static inline struct basic_block *bb_entry(struct list_head
*head)
return list_entry(head, struct basic_block, bb_list_node);
}
+static inline bool bb_is_empty(struct basic_block *bb)
+{
+ return list_is_empty(&bb->stmt_list);
+}
+
struct basic_block *alloc_basic_block(struct compilation_unit *, unsigned
long, unsigned long);
struct basic_block *get_basic_block(struct compilation_unit *, unsigned long,
unsigned long);
void free_basic_block(struct basic_block *);
diff --git a/jit/basic-block.c b/jit/basic-block.c
index 6de5c3f..0f40bcc 100644
--- a/jit/basic-block.c
+++ b/jit/basic-block.c
@@ -176,21 +176,14 @@ struct insn *bb_first_insn(struct basic_block *bb)
struct insn *bb_last_insn(struct basic_block *bb)
{
- struct insn *this = list_entry(bb->insn_list.prev, struct insn,
insn_list_node);
-
- /*
- * We want to return the last "real" instruction of the basic block.
Taking the
- * last of the insn_list will not work in case a live interval has been
spilled
- * right after the final jump of the basic block.
- * This is a side effect of the linear scan algorithm.
- *
- * As a result, we browse instructions starting from the last, in order
to find the one
- * that has a LIR position matching the position for the end of the
block.
- */
- while (this->lir_pos != bb->end_insn - 1) {
- this = list_entry(this->insn_list_node.prev, struct insn,
insn_list_node);
- }
- return this;
+ unsigned long pos = bb->end_insn - 1;
+
+ if (bb_is_empty(bb))
+ return NULL;
+
+ assert(pos >= bb->start_insn);
+
+ return radix_tree_lookup(bb->b_parent->lir_insn_map, pos);
}
static int __bb_add_neighbor(void *new, void **array, unsigned long *nb)
diff --git a/jit/spill-reload.c b/jit/spill-reload.c
index 5ced80e..a8806f1 100644
--- a/jit/spill-reload.c
+++ b/jit/spill-reload.c
@@ -183,7 +183,8 @@ static void insert_mov_insns(struct compilation_unit *cu,
struct insn *spill_at_insn;
int i;
- spill_at_insn = bb_last_insn(from_bb);
+ spill_at_insn = bb_last_insn(from_bb);
+ assert(spill_at_insn != NULL);
/* Spill all intervals that have to be resolved */
for (i = 0; i < nr_mapped; i++) {
--
1.5.6.3
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