From dc511bf288450b2ca571292b7cc0e2a081d5ef78 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 23 Feb 2021 13:11:57 -0800
Subject: [PATCH 1/3] fix

---
 src/wasm-stack.h                              |  2 ++
 src/wasm/wasm-stack.cpp                       |  5 +++
 ...nerate-stack-ir_roundtrip_all-features.txt | 32 +++++++++++++++++++
 ...erate-stack-ir_roundtrip_all-features.wast | 27 ++++++++++++++++
 4 files changed, 66 insertions(+)
 create mode 100644 test/passes/generate-stack-ir_roundtrip_all-features.txt
 create mode 100644 test/passes/generate-stack-ir_roundtrip_all-features.wast

diff --git a/src/wasm-stack.h b/src/wasm-stack.h
index 7f94573fa5f..5af9adbce4f 100644
--- a/src/wasm-stack.h
+++ b/src/wasm-stack.h
@@ -350,6 +350,8 @@ template<typename SubType> void BinaryenIRWriter<SubType>::visitTry(Try* curr) {
   }
   if (curr->isDelegate()) {
     emitDelegate(curr);
+    // Note that when we emit a delegate we do not need to also emit a scope
+    // ending, as the delegate ends the scope.
   } else {
     emitScopeEnd(curr);
   }
diff --git a/src/wasm/wasm-stack.cpp b/src/wasm/wasm-stack.cpp
index b6c0392ca04..4c4e4e9d1a3 100644
--- a/src/wasm/wasm-stack.cpp
+++ b/src/wasm/wasm-stack.cpp
@@ -1925,6 +1925,9 @@ void BinaryInstWriter::emitCatchAll(Try* curr) {
 }
 
 void BinaryInstWriter::emitDelegate(Try* curr) {
+  // The delegate ends the scope in effect, and pops the try's name. Note that
+  // the getBreakIndex is intentionally after that pop, as the delegate cannot
+  // target its own try.
   assert(!breakStack.empty());
   breakStack.pop_back();
   o << int8_t(BinaryConsts::Delegate)
@@ -2333,6 +2336,8 @@ void StackIRToBinaryWriter::write() {
       }
       case StackInst::Delegate: {
         writer.emitDelegate(inst->origin->cast<Try>());
+        // Delegates end the try, like a TryEnd.
+        catchIndexStack.pop_back();
         break;
       }
       default:
diff --git a/test/passes/generate-stack-ir_roundtrip_all-features.txt b/test/passes/generate-stack-ir_roundtrip_all-features.txt
new file mode 100644
index 00000000000..3d06adff189
--- /dev/null
+++ b/test/passes/generate-stack-ir_roundtrip_all-features.txt
@@ -0,0 +1,32 @@
+(module
+ (type $none_=>_none (func))
+ (type $i32_=>_none (func (param i32)))
+ (event $event$0 (attr 0) (param i32))
+ (func $delegate-child
+  (try $label$9
+   (do
+    (try $label$7
+     (do
+      (nop)
+     )
+     (catch $event$0
+      (drop
+       (pop i32)
+      )
+      (try $label$6
+       (do
+        (nop)
+       )
+       (delegate 2)
+      )
+     )
+    )
+   )
+   (catch $event$0
+    (drop
+     (pop i32)
+    )
+   )
+  )
+ )
+)
diff --git a/test/passes/generate-stack-ir_roundtrip_all-features.wast b/test/passes/generate-stack-ir_roundtrip_all-features.wast
new file mode 100644
index 00000000000..1230e3cf17d
--- /dev/null
+++ b/test/passes/generate-stack-ir_roundtrip_all-features.wast
@@ -0,0 +1,27 @@
+(module
+ (event $event (attr 0) (param i32))
+ (func $delegate-child
+  (try
+   (do
+    (try
+     (do)
+     (catch $event
+      (drop
+       (pop i32)
+      )
+      (try
+       (do)
+       (delegate 2)
+      )
+     )
+    )
+   )
+   (catch $event
+    (drop
+     (pop i32)
+    )
+   )
+  )
+ )
+)
+

From d7b1576eaa7276a95aa6dd6426125a448c426132 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 23 Feb 2021 13:14:10 -0800
Subject: [PATCH 2/3] comment

---
 test/passes/generate-stack-ir_roundtrip_all-features.wast | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/test/passes/generate-stack-ir_roundtrip_all-features.wast b/test/passes/generate-stack-ir_roundtrip_all-features.wast
index 1230e3cf17d..8a04eabf8a3 100644
--- a/test/passes/generate-stack-ir_roundtrip_all-features.wast
+++ b/test/passes/generate-stack-ir_roundtrip_all-features.wast
@@ -11,6 +11,10 @@
       )
       (try
        (do)
+       ;; the binary writer must properly handle this delegate which is the
+       ;; child of other try's, and not get confused by their information on the
+       ;; stack (this is a regression test for us properly ending the scope with
+       ;; a delegate and popping the stack of break targets).
        (delegate 2)
       )
      )

From 2fdcefadd99358cb084081cf6d90d3d6231fac6b Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 23 Feb 2021 13:15:52 -0800
Subject: [PATCH 3/3] fix comment

---
 test/passes/generate-stack-ir_roundtrip_all-features.wast | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/passes/generate-stack-ir_roundtrip_all-features.wast b/test/passes/generate-stack-ir_roundtrip_all-features.wast
index 8a04eabf8a3..dc6c68d672a 100644
--- a/test/passes/generate-stack-ir_roundtrip_all-features.wast
+++ b/test/passes/generate-stack-ir_roundtrip_all-features.wast
@@ -14,7 +14,7 @@
        ;; the binary writer must properly handle this delegate which is the
        ;; child of other try's, and not get confused by their information on the
        ;; stack (this is a regression test for us properly ending the scope with
-       ;; a delegate and popping the stack of break targets).
+       ;; a delegate and popping the relevant stack).
        (delegate 2)
       )
      )