[PATCH 2/7] jit: fix verify_correct_nesting() and add verify_no_recursion()

[Tomek Grabiec]

verify_no_recursion() checks whether all call sites of given subroutine
all outside its body. It's a requirement for inlining to be possible.

Signed-off-by: Tomek Grabiec <tgrab...@gmail.com>
---
 jit/subroutine.c |   34 ++++++++++++++++++++++++++++++----
 1 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/jit/subroutine.c b/jit/subroutine.c
index e831d17..4026104 100644
--- a/jit/subroutine.c
+++ b/jit/subroutine.c
@@ -843,6 +843,16 @@ update_and_copy_exception_handlers(struct inlining_context 
*ctx,
        return 0;
 }
 
+static int verify_no_recursion(struct subroutine *sub)
+{
+       for (int i = 0; i < sub->nr_call_sites; i++)
+               if (sub->call_sites[i] > sub->start_pc &&
+                   sub->call_sites[i] < sub->end_pc)
+                       return warn("subroutine recursion"), -EINVAL;
+
+       return 0;
+}
+
 static int do_inline_subroutine(struct inlining_context *ctx,
                                struct subroutine *sub)
 {
@@ -866,6 +876,10 @@ static int do_inline_subroutine(struct inlining_context 
*ctx,
        if (err)
                goto error_update_bytecode_offsets;
 
+       err = verify_no_recursion(sub);
+       if (err)
+               goto error_update_bytecode_offsets;
+
        unsigned long body_size = subroutine_get_body_size(sub);
        unsigned long sub_size = subroutine_get_size(sub);
        unsigned long new_code_length = ctx->code.code_length - sub_size +
@@ -873,7 +887,7 @@ static int do_inline_subroutine(struct inlining_context 
*ctx,
                sub->call_sites_total_size;
 
        if (code_state_init_empty(&new_code, new_code_length))
-               goto error_new_code;
+               goto error_update_bytecode_offsets;
 
        subroutine_sort_call_sites(sub);
 
@@ -935,7 +949,6 @@ static int do_inline_subroutine(struct inlining_context 
*ctx,
 
  error:
        code_state_deinit(&new_code);
- error_new_code:
  error_update_bytecode_offsets:
        pc_map_deinit(&pc_map);
 
@@ -1088,13 +1101,26 @@ static int split_exception_handlers(struct 
inlining_context *ctx)
 static int verify_correct_nesting(struct inlining_context *ctx)
 {
        struct subroutine *this;
+       int *coverage;
+
+       coverage = zalloc(ctx->code.code_length * sizeof(int));
+       if (!coverage)
+               return -ENOMEM;
 
        list_for_each_entry(this, &ctx->subroutine_list, subroutine_list_node) {
-               for (int i = 0; i < this->nr_dependants; i++)
-                       if (this->end_pc > this->dependants[i]->end_pc)
+               int color = coverage[this->start_pc];
+
+               for (unsigned long i = this->start_pc; i < this->end_pc; i++) {
+                       if (coverage[i] != color) {
+                               free(coverage);
                                return warn("overlaping subroutines"), -EINVAL;
+                       }
+
+                       coverage[i]++;
+               }
        }
 
+       free(coverage);
        return 0;
 }
 
-- 
1.6.0.6


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