From 3ff8867e5785bf7ea74bd60b4cdeacf040da7c8c Mon Sep 17 00:00:00 2001
From: Dan Gohman <sunfish@mozilla.com>
Date: Fri, 26 Oct 2018 06:20:08 -0700
Subject: [PATCH] Split the default edge of a br_table.

When splitting critical edges for a br_table to handle arguments being
passed, split the default edge along with the normal table edges.
---
 cranelift/wasmtests/br_table.wat | 30 ++++++++++++++++++++++++++++++
 lib/wasm/src/code_translator.rs  | 17 +++++++++--------
 2 files changed, 39 insertions(+), 8 deletions(-)
 create mode 100644 cranelift/wasmtests/br_table.wat

diff --git a/cranelift/wasmtests/br_table.wat b/cranelift/wasmtests/br_table.wat
new file mode 100644
index 0000000000..75444fa49c
--- /dev/null
+++ b/cranelift/wasmtests/br_table.wat
@@ -0,0 +1,30 @@
+(module
+  (func (result i32)
+    (block (result i32)
+      (block (result i32)
+        (block (result i32)
+          (br_table 0 1 2 3 (i32.const 42) (i32.const 0))
+        )
+      )
+    )
+  )
+  (func (result i32)
+    (block (result i32)
+      (block (result i32)
+        (block (result i32)
+          (br_table 3 2 1 0 (i32.const 42) (i32.const 0))
+        )
+      )
+    )
+  )
+  (func (result i32)
+    (block (result i32)
+      (br_table 0 0 1 1 (i32.const 42) (i32.const 0))
+    )
+  )
+  (func (result i32)
+    (block (result i32)
+      (br_table 1 1 0 0 (i32.const 42) (i32.const 0))
+    )
+  )
+)
diff --git a/lib/wasm/src/code_translator.rs b/lib/wasm/src/code_translator.rs
index e7a62b65fe..8d5fee979a 100644
--- a/lib/wasm/src/code_translator.rs
+++ b/lib/wasm/src/code_translator.rs
@@ -307,15 +307,16 @@ pub fn translate_operator<FE: FuncEnvironment + ?Sized>(
                     };
                     data.push_entry(branch_ebb);
                 }
-                let jt = builder.create_jump_table(data);
-                let default_ebb = {
-                    let i = state.control_stack.len() - 1 - (default as usize);
-                    let frame = &mut state.control_stack[i];
-                    frame.set_branched_to_exit();
-                    frame.br_destination()
+                let default_branch_ebb = match dest_ebb_map.entry(default as usize) {
+                    hash_map::Entry::Occupied(entry) => *entry.get(),
+                    hash_map::Entry::Vacant(entry) => {
+                        let ebb = builder.create_ebb();
+                        dest_ebb_sequence.push((default as usize, ebb));
+                        *entry.insert(ebb)
+                    }
                 };
-                dest_ebb_sequence.push((default as usize, default_ebb));
-                builder.ins().br_table(val, default_ebb, jt);
+                let jt = builder.create_jump_table(data);
+                builder.ins().br_table(val, default_branch_ebb, jt);
                 for (depth, dest_ebb) in dest_ebb_sequence {
                     builder.switch_to_block(dest_ebb);
                     builder.seal_block(dest_ebb);