improve bytecode printing w/ padding and AST locations

Summary:
In developing D73038348, it was helpful to have the annotated source locations displayed in the bytecode dumps.

This also computes the maximum length used to display an `IP` value, and padds all such values so that all of the `:` for a particular loop depth are aligned.

Reviewed By: cjhopman

Differential Revision: D73038341

fbshipit-source-id: 914e044a014fb19859f5c1817d94a1a57b2dca38

Author: Jeremy Braun

starlark/src/eval/bc/instrs.rs

@@ -218,6 +218,12 @@ impl BcInstrs {
 
     pub(crate) fn fmt_impl(&self, f: &mut dyn Write, newline: bool) -> fmt::Result {
         let end_arg = self.end_arg();
+        let ip_pad = if newline {
+            let max_ip = self.iter().map(|(_, ip)| ip).max().unwrap_or(BcAddr(0));
+            format!("{}", (max_ip).0).len()
+        } else {
+            0
+        };
 
         let mut loop_ends = Vec::new();
         let mut jump_targets = HashSet::new();
@@ -227,13 +233,21 @@ impl BcInstrs {
             });
         }
         for (ptr, ip) in self.iter() {
-            if ptr != self.start_ptr() && !newline {
-                write!(f, "; ")?;
-            }
-
             if loop_ends.last() == Some(&ip) {
                 loop_ends.pop().unwrap();
             }
+            let loop_pad = loop_ends.len() * 2;
+
+            if newline {
+                if let Some(loc) = self.stmt_locs.stmt_at(ip) {
+                    writeln!(f, "{:loop_pad$} {:ip_pad$}  # {}", "", "", loc.span.span)?;
+                }
+            } else {
+                if ptr != self.start_ptr() {
+                    write!(f, "; ")?;
+                }
+            }
+
             let opcode = ptr.get_opcode();
             if !jump_targets.is_empty() {
                 if jump_targets.contains(&ip) {
@@ -243,11 +257,9 @@ impl BcInstrs {
                 }
             }
             if newline {
-                for _ in &loop_ends {
-                    write!(f, "  ")?;
-                }
+                write!(f, "{:loop_pad$}", "")?;
             }
-            write!(f, "{}: {:?}", ip.0, opcode)?;
+            write!(f, "{:ip_pad$}: {:?}", ip.0, opcode)?;
             if opcode != BcOpcode::End {
                 // `End` args are too verbose and not really instruction args.
                 opcode.fmt_append_arg(ptr, ip, end_arg, f)?;
@@ -402,7 +414,7 @@ mod tests {
                 bc.to_string()
             );
             assert_eq!(
-                "0: Const True ->&abc\n24: Return &abc\n32: End\n",
+                " 0: Const True ->&abc\n24: Return &abc\n32: End\n",
                 bc.dump_debug()
             );
         } else if mem::size_of::<usize>() == 4 {

starlark/src/tests/bc/golden/and_or_false_and_x.golden

@@ -10,5 +10,6 @@ def test(x): return False and x
 
 Max stack size: 0
 Instructions:
-  0: ReturnConst False
+       # instrs.star.bzl:1:14-32
+   0: ReturnConst False
   16: End

starlark/src/tests/bc/golden/and_or_false_or_x.golden

@@ -10,5 +10,6 @@ def test(x): return False or x
 
 Max stack size: 0
 Instructions:
+      # instrs.star.bzl:1:14-31
   0: Return &x
   8: End

starlark/src/tests/bc/golden/and_or_true_and_x.golden

@@ -10,5 +10,6 @@ def test(x): return True and x
 
 Max stack size: 0
 Instructions:
+      # instrs.star.bzl:1:14-31
   0: Return &x
   8: End

starlark/src/tests/bc/golden/and_or_true_or_x.golden

@@ -10,5 +10,6 @@ def test(x): return True or x
 
 Max stack size: 0
 Instructions:
-  0: ReturnConst True
+       # instrs.star.bzl:1:14-30
+   0: ReturnConst True
   16: End

starlark/src/tests/bc/golden/and_or_x_and_false.golden

@@ -10,7 +10,8 @@ def test(x): return x and False
 
 Max stack size: 1
 Instructions:
-   0: IfNotBr &x 48
+       # instrs.star.bzl:1:14-32
+    0: IfNotBr &x 48
    16: Const False ->&1
    40: Br 64
   >48: Mov &x ->&1

starlark/src/tests/bc/golden/and_or_x_and_true.golden

@@ -10,7 +10,8 @@ def test(x): return x and True
 
 Max stack size: 1
 Instructions:
-   0: IfNotBr &x 48
+       # instrs.star.bzl:1:14-31
+    0: IfNotBr &x 48
    16: Const True ->&1
    40: Br 64
   >48: Mov &x ->&1

starlark/src/tests/bc/golden/and_or_x_or_false.golden

@@ -10,7 +10,8 @@ def test(x): return x or False
 
 Max stack size: 1
 Instructions:
-   0: IfNotBr &x 40
+       # instrs.star.bzl:1:14-31
+    0: IfNotBr &x 40
    16: Mov &x ->&1
    32: Br 64
   >40: Const False ->&1

starlark/src/tests/bc/golden/and_or_x_or_true.golden

@@ -10,7 +10,8 @@ def test(x): return x or True
 
 Max stack size: 1
 Instructions:
-   0: IfNotBr &x 40
+       # instrs.star.bzl:1:14-30
+    0: IfNotBr &x 40
    16: Mov &x ->&1
    32: Br 64
   >40: Const True ->&1

starlark/src/tests/bc/golden/call.golden

@@ -19,11 +19,12 @@ def test(a, k):
 
 Max stack size: 6
 Instructions:
-  0: Const 10 ->&3
-  24: Const 20 ->&4
-  48: Const 30 ->&5
-  72: Const 40 ->&6
-  96: Const 50 ->&7
+        # instrs.star.bzl:2:5-10:6
+    0: Const 10 ->&3
+   24: Const 20 ->&4
+   48: Const 30 ->&5
+   72: Const 40 ->&6
+   96: Const 50 ->&7
   120: CallFrozenNative noop {&3..&8 2 p q r *&0 **&1} instrs.star.bzl:2:5-10:6 ->&2
   208: ReturnConst None
   224: End