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YJIT: Fix raw sample stack lengths in exit traces (#7728)

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yjit-trace-exits appends a synthetic sample for the instruction being
exited, but we didn't increment the size of the stack. Fixing this count
correctly lets us successfully generate a flamegraph from the exits.

I also replaced the line number for instructions with 0, as I don't
think the previous value had meaning.

Co-authored-by: Adam Hess <HParker@github.com>
This commit is contained in:
John Hawthorn 2023-04-18 07:09:16 -07:00 committed by GitHub
parent d8a6db7292
commit 2dff1d4fda
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Notes: git 2023-04-18 14:11:18 +00:00 
Merged-By: maximecb <maximecb@ruby-lang.org>
3 changed files with 6 additions and 7 deletions
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5
yjit.c
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@ -186,8 +186,9 @@ rb_yjit_exit_locations_dict(VALUE *yjit_raw_samples, int *yjit_line_samples, int
int line_num = (int)yjit_line_samples[idx]; int line_num = (int)yjit_line_samples[idx];
idx++; idx++;
rb_ary_push(raw_samples, SIZET2NUM(num)); // + 1 as we append an additional sample for the insn
rb_ary_push(line_samples, INT2NUM(line_num)); rb_ary_push(raw_samples, SIZET2NUM(num + 1));
rb_ary_push(line_samples, INT2NUM(line_num + 1));
// Loop through the length of samples_len and add data to the // Loop through the length of samples_len and add data to the
// frames hash. Also push the current value onto the raw_samples // frames hash. Also push the current value onto the raw_samples

2
yjit.rb
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@ -67,7 +67,7 @@ module RubyVM::YJIT
# [ length, line_1, line_2, line_n, ..., dummy value, count # [ length, line_1, line_2, line_n, ..., dummy value, count
i = 0 i = 0
while i < raw_samples.length while i < raw_samples.length
stack_length = raw_samples[i] + 1 stack_length = raw_samples[i]
i += 1 # consume the stack length i += 1 # consume the stack length
sample_count = raw_samples[i + stack_length] sample_count = raw_samples[i + stack_length]

6
yjit/src/stats.rs
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@ -724,10 +724,8 @@ pub extern "C" fn rb_yjit_record_exit_stack(exit_pc: *const VALUE)
// Push the insn value into the yjit_raw_samples Vec. // Push the insn value into the yjit_raw_samples Vec.
yjit_raw_samples.push(VALUE(insn as usize)); yjit_raw_samples.push(VALUE(insn as usize));
// Push the current line onto the yjit_line_samples Vec. This // We don't know the line
// points to the line in insns.def. yjit_line_samples.push(0);
let line = yjit_line_samples.len() - 1;
yjit_line_samples.push(line as i32);
// Push number of times seen onto the stack, which is 1 // Push number of times seen onto the stack, which is 1
// because it's the first time we've seen it. // because it's the first time we've seen it.