Speed up --yjit-trace-exits code (#6106)

In a small script the speed of this feature isn't really noticeable but
on Rails it's very noticeable how slow this can be. This PR aims to
speed up two parts of the functionality.

1) The Rust exit recording code

Instead of adding all samples as we see them to the yjit_raw_samples and
yjit_line_samples, we can increment the counter on the ones we've seen
before. This will be faster on traces where we are hitting the same
stack often. In a crude measurement of booting just the active record
base test (`test/cases/base_test.rb`) we found that this improved the
speed by 1 second.

This also results in a smaller marshal dump file which sped up the test
boot time by 4 seconds with trace exits on.

2) The Ruby parsing code

Previously we were allocating new arrays using `shift` and
`each_with_index`. This change avoids allocating new arrays by using an
index. This change saves us the most amount of time, gaining 11 seconds.

Before this change the test boot time took 62 seconds, after it took 47
seconds. This is still too long but it's a step closer to faster
functionality. Next we're going to tackle allowing you to collect trace
exits for a specific instruction. There is also some potential slowness
in the GC code that I'd like to take a second look at.

Co-authored-by: Aaron Patterson <[email protected]>

Co-authored-by: Aaron Patterson <[email protected]>

1 files changed, 4 insertions, 0 deletions

diff --git a/yjit.c b/yjit.c
index 108a376282..daf608b106 100644
--- a/yjit.c
+++ b/yjit.c
@@ -107,6 +107,10 @@ rb_yjit_add_frame(VALUE hash, VALUE frame)
 
         rb_hash_aset(frame_info, ID2SYM(rb_intern("name")), name);
         rb_hash_aset(frame_info, ID2SYM(rb_intern("file")), file);
+        rb_hash_aset(frame_info, ID2SYM(rb_intern("samples")), INT2NUM(0));
+        rb_hash_aset(frame_info, ID2SYM(rb_intern("total_samples")), INT2NUM(0));
+        rb_hash_aset(frame_info, ID2SYM(rb_intern("edges")), rb_hash_new());
+        rb_hash_aset(frame_info, ID2SYM(rb_intern("lines")), rb_hash_new());
 
         if (line != INT2FIX(0)) {
             rb_hash_aset(frame_info, ID2SYM(rb_intern("line")), line);