From 8560f431f38ad2b359c2caa8652a93e174f0695a Mon Sep 17 00:00:00 2001
From: Yury Delendik <ydelendik@mozilla.com>
Date: Thu, 28 Feb 2019 12:42:48 -0600
Subject: [PATCH] Extend .debug_line info to the generated code range.

---
 lib/debug/src/address_transform.rs | 17 ++++++++++++++---
 lib/debug/src/transform.rs         | 27 ++++++++++++++++-----------
 2 files changed, 30 insertions(+), 14 deletions(-)

diff --git a/lib/debug/src/address_transform.rs b/lib/debug/src/address_transform.rs
index f8eff81d0dfc..8f19ecddf1b1 100644
--- a/lib/debug/src/address_transform.rs
+++ b/lib/debug/src/address_transform.rs
@@ -17,10 +17,17 @@ pub struct AddressMap {
     pub wasm: WasmAddress,
 }
 
+#[derive(Debug)]
+pub struct FunctionMap {
+    pub offset: GeneratedAddress,
+    pub len: GeneratedAddress,
+    pub addresses: Box<[AddressMap]>,
+}
+
 #[derive(Debug)]
 pub struct AddressTransform {
     lookup: BTreeMap<WasmAddress, (SymbolIndex, GeneratedAddress, GeneratedAddress)>,
-    map: PrimaryMap<DefinedFuncIndex, Box<[AddressMap]>>,
+    map: PrimaryMap<DefinedFuncIndex, FunctionMap>,
     func_ranges: Vec<(usize, usize)>,
 }
 
@@ -63,7 +70,11 @@ impl AddressTransform {
             let last_addr = ft.body_offset + ft.body_len;
             lookup.insert(fn_offset + fn_size, (index, last_addr, last_addr));
             fn_map.sort_by(|a, b| a.generated.cmp(&b.generated));
-            map.push(fn_map.into_boxed_slice());
+            map.push(FunctionMap {
+                offset: ft.body_offset,
+                len: ft.body_len,
+                addresses: fn_map.into_boxed_slice(),
+            });
         }
         AddressTransform {
             lookup,
@@ -118,7 +129,7 @@ impl AddressTransform {
         self.diff(addr1, addr1 + u)
     }
 
-    pub fn map(&self) -> &PrimaryMap<DefinedFuncIndex, Box<[AddressMap]>> {
+    pub fn map(&self) -> &PrimaryMap<DefinedFuncIndex, FunctionMap> {
         &self.map
     }
 
diff --git a/lib/debug/src/transform.rs b/lib/debug/src/transform.rs
index ff2a9d48111e..114dac3b1d65 100644
--- a/lib/debug/src/transform.rs
+++ b/lib/debug/src/transform.rs
@@ -368,14 +368,12 @@ where
         }
 
         for (i, map) in addr_tr.map() {
-            if map.len() == 0 {
-                continue;
-            }
             let symbol = i.index();
-            let base_addr = map[0].generated; // Assume it where function symbol starts at
+            let base_addr = map.offset;
             out_program.begin_sequence(Some(write::Address::Relative { symbol, addend: 0 }));
-            let mut last_address = base_addr as u64;
-            for addr_map in map.iter() {
+            // TODO track and place function declaration line here
+            let mut last_address = None;
+            for addr_map in map.addresses.iter() {
                 let mut saved_row = saved_rows.get(&addr_map.wasm);
                 if saved_row.is_none() {
                     // No direct match -- repeat search with range.
@@ -399,8 +397,15 @@ where
                 }) = saved_row
                 {
                     // Ignore duplicates
-                    if *address != last_address {
-                        out_program.row().address_offset = (addr_map.generated - base_addr) as u64;
+                    if Some(*address) != last_address {
+                        let address_offset = if last_address.is_none() {
+                            // Extend first entry to the function declaration
+                            // TODO use the function declaration line instead
+                            0
+                        } else {
+                            (addr_map.generated - base_addr) as u64
+                        };
+                        out_program.row().address_offset = address_offset;
                         out_program.row().op_index = *op_index;
                         out_program.row().file = files[(file_index - 1) as usize];
                         out_program.row().line = *line;
@@ -412,12 +417,12 @@ where
                         out_program.row().epilogue_begin = *epilogue_begin;
                         out_program.row().isa = *isa;
                         out_program.generate_row();
-                        last_address = *address;
+                        last_address = Some(*address);
                     }
                 }
             }
-            let last_addr = (map[map.len() - 1].generated - base_addr) as u64;
-            out_program.end_sequence(last_addr);
+            let end_addr = (map.offset + map.len - 1) as u64;
+            out_program.end_sequence(end_addr);
         }
         Ok((out_program, offset, files))
     } else {