refactor(tvix/eval): implement much clearer disassembler output r/4752

With this change the runtime trace contains much more exact
information about the context of the computation (entering/exiting
calls etc.)

This is in large part due to moving the tracer to be a field on the VM
itself, which enables consistent ordering of traces across the
execution, and tracing an execution with its *input* instead
of *output* stack.

Change-Id: Ibe525e6e7d869756501e52bef1a441619ce7332c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6419
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI

1 files changed, 5 insertions, 3 deletions

diff --git a/tvix/eval/src/disassembler.rs b/tvix/eval/src/disassembler.rs
index e3cc1f16e706..a555f9179102 100644
--- a/tvix/eval/src/disassembler.rs
+++ b/tvix/eval/src/disassembler.rs
@@ -15,9 +15,7 @@ pub struct Tracer(TabWriter<Stderr>);
 
 impl Tracer {
     pub fn new() -> Self {
-        let mut tw = TabWriter::new(std::io::stderr());
-        write!(&mut tw, "=== runtime trace ===\n").ok();
-        Tracer(tw)
+        Tracer(TabWriter::new(std::io::stderr()))
     }
 
     pub fn trace(&mut self, op: &OpCode, ip: usize, stack: &[Value]) {
@@ -29,6 +27,10 @@ impl Tracer {
 
         write!(&mut self.0, "]\n").ok();
     }
+
+    pub fn literal(&mut self, line: &str) {
+        let _ = write!(&mut self.0, "{}\n", line);
+    }
 }
 
 impl Drop for Tracer {