From 5f6911f1f1fcae058bf77720f04e1166bafca8e3 Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Mon, 29 Nov 2021 13:57:05 -0800
Subject: Handle try in Flatten pass (#2567)

This adds handling of try in the Flatten pass.
---
 src/ir/eh-utils.cpp    |  4 ++++
 src/passes/Flatten.cpp | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+)

(limited to 'src')

diff --git a/src/ir/eh-utils.cpp b/src/ir/eh-utils.cpp
index ed7ec1e0a..31ddfe306 100644
--- a/src/ir/eh-utils.cpp
+++ b/src/ir/eh-utils.cpp
@@ -108,6 +108,10 @@ bool isPopValid(Expression* catchBody) {
 }
 
 void handleBlockNestedPops(Function* func, Module& wasm) {
+  if (!wasm.features.hasExceptionHandling()) {
+    return;
+  }
+
   Builder builder(wasm);
   FindAll<Try> trys(func->body);
   for (auto* try_ : trys.list) {
diff --git a/src/passes/Flatten.cpp b/src/passes/Flatten.cpp
index 298b6241e..be43e57f2 100644
--- a/src/passes/Flatten.cpp
+++ b/src/passes/Flatten.cpp
@@ -41,6 +41,7 @@
 
 #include <ir/branch-utils.h>
 #include <ir/effects.h>
+#include <ir/eh-utils.h>
 #include <ir/flat.h>
 #include <ir/properties.h>
 #include <ir/type-updating.h>
@@ -192,6 +193,37 @@ struct Flatten
         loop->finalize();
         replaceCurrent(rep);
 
+      } else if (auto* tryy = curr->dynCast<Try>()) {
+        // remove a try value
+        Expression* rep = tryy;
+        auto* originalBody = tryy->body;
+        std::vector<Expression*> originalCatchBodies(tryy->catchBodies.begin(),
+                                                     tryy->catchBodies.end());
+        auto type = tryy->type;
+        if (type.isConcrete()) {
+          Index temp = builder.addVar(getFunction(), type);
+          if (tryy->body->type.isConcrete()) {
+            tryy->body = builder.makeLocalSet(temp, tryy->body);
+          }
+          for (Index i = 0; i < tryy->catchBodies.size(); i++) {
+            if (tryy->catchBodies[i]->type.isConcrete()) {
+              tryy->catchBodies[i] =
+                builder.makeLocalSet(temp, tryy->catchBodies[i]);
+            }
+          }
+          // and we leave just a get of the value
+          rep = builder.makeLocalGet(temp, type);
+          // the whole try is now a prelude
+          ourPreludes.push_back(tryy);
+        }
+        tryy->body = getPreludesWithExpression(originalBody, tryy->body);
+        for (Index i = 0; i < tryy->catchBodies.size(); i++) {
+          tryy->catchBodies[i] = getPreludesWithExpression(
+            originalCatchBodies[i], tryy->catchBodies[i]);
+        }
+        tryy->finalize();
+        replaceCurrent(rep);
+
       } else {
         WASM_UNREACHABLE("unexpected expr type");
       }
@@ -347,6 +379,10 @@ struct Flatten
                 << type;
       }
     }
+
+    // Flatten can generate blocks within 'catch', making pops invalid. Fix them
+    // up.
+    EHUtils::handleBlockNestedPops(curr, *getModule());
   }
 
 private:
-- 
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