10 files changed, 116 insertions, 5 deletions
diff --git a/build-js.sh b/build-js.sh
index 808329386..f9553e3e4 100755
--- a/build-js.sh
+++ b/build-js.sh
@@ -115,6 +115,7 @@ echo "building shared bitcode"
   $BINARYEN_SRC/passes/Metrics.cpp \
   $BINARYEN_SRC/passes/MinifyImportsAndExports.cpp \
   $BINARYEN_SRC/passes/NameList.cpp \
+  $BINARYEN_SRC/passes/NoExitRuntime.cpp \
   $BINARYEN_SRC/passes/OptimizeInstructions.cpp \
   $BINARYEN_SRC/passes/PickLoadSigns.cpp \
   $BINARYEN_SRC/passes/PostEmscripten.cpp \
diff --git a/src/passes/CMakeLists.txt b/src/passes/CMakeLists.txt
index b4e396750..0ad9dbf05 100644
--- a/src/passes/CMakeLists.txt
+++ b/src/passes/CMakeLists.txt
@@ -30,6 +30,7 @@ SET(passes_SOURCES
   Metrics.cpp
   MinifyImportsAndExports.cpp
   NameList.cpp
+  NoExitRuntime.cpp
   OptimizeInstructions.cpp
   PickLoadSigns.cpp
   PostEmscripten.cpp
diff --git a/src/passes/Inlining.cpp b/src/passes/Inlining.cpp
index ebc33bf97..35afc5776 100644
--- a/src/passes/Inlining.cpp
+++ b/src/passes/Inlining.cpp
@@ -349,11 +349,11 @@ struct Inlining : public Pass {
   }
 };
 
-Pass *createInliningPass() {
+Pass* createInliningPass() {
   return new Inlining();
 }
 
-Pass *createInliningOptimizingPass() {
+Pass* createInliningOptimizingPass() {
   auto* ret = new Inlining();
   ret->optimize = true;
   return ret;
diff --git a/src/passes/MergeBlocks.cpp b/src/passes/MergeBlocks.cpp
index 57f8b7e41..38e9fc6a2 100644
--- a/src/passes/MergeBlocks.cpp
+++ b/src/passes/MergeBlocks.cpp
@@ -373,7 +373,7 @@ struct MergeBlocks : public WalkerPass<PostWalker<MergeBlocks>> {
 
   Pass* create() override { return new MergeBlocks; }
 
-  void visitBlock(Block *curr) {
+  void visitBlock(Block* curr) {
     optimizeBlock(curr, getModule(), getPassOptions());
   }
 
diff --git a/src/passes/Metrics.cpp b/src/passes/Metrics.cpp
index 5176f8762..b794ea32d 100644
--- a/src/passes/Metrics.cpp
+++ b/src/passes/Metrics.cpp
@@ -194,11 +194,11 @@ struct Metrics : public WalkerPass<PostWalker<Metrics, UnifiedExpressionVisitor<
   }
 };
 
-Pass *createMetricsPass() {
+Pass* createMetricsPass() {
   return new Metrics(false);
 }
 
-Pass *createFunctionMetricsPass() {
+Pass* createFunctionMetricsPass() {
   return new Metrics(true);
 }
 
diff --git a/src/passes/NoExitRuntime.cpp b/src/passes/NoExitRuntime.cpp
new file mode 100644
index 000000000..d76bb34ba
--- /dev/null
+++ b/src/passes/NoExitRuntime.cpp
@@ -0,0 +1,60 @@
+/*
+ * Copyright 2016 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//
+// Assumes the program will never exit the runtime (as in the emscripten
+// NO_EXIT_RUNTIME option). That means that atexit()s do not need to be
+// run.
+//
+
+#include <pass.h>
+#include <wasm.h>
+#include <wasm-builder.h>
+#include <asmjs/shared-constants.h>
+
+using namespace std;
+
+namespace wasm {
+
+struct NoExitRuntime : public WalkerPass<PostWalker<NoExitRuntime>> {
+  bool isFunctionParallel() override { return true; }
+
+  Pass* create() override { return new NoExitRuntime; }
+
+  void visitCall(Call* curr) {
+    auto* import = getModule()->getFunctionOrNull(curr->target);
+    if (!import || !import->imported() || import->module != ENV) return;
+    // Remove all possible manifestations of atexit, across asm2wasm and llvm wasm backend.
+    for (auto* name : {
+      "___cxa_atexit",
+      "_atexit",
+      "__cxa_atexit",
+      "atexit",
+    }) {
+      if (strcmp(name, import->base.str) == 0) {
+        replaceCurrent(
+          Builder(*getModule()).replaceWithIdenticalType(curr)
+        );
+      }
+    }
+  }
+};
+
+Pass* createNoExitRuntimePass() {
+  return new NoExitRuntime();
+}
+
+} // namespace wasm
diff --git a/src/passes/pass.cpp b/src/passes/pass.cpp
index c42a3d144..f250b7de6 100644
--- a/src/passes/pass.cpp
+++ b/src/passes/pass.cpp
@@ -98,6 +98,7 @@ void PassRegistry::registerPasses() {
   registerPass("minify-imports", "minifies import names (only those, and not export names), and emits a mapping to the minified ones", createMinifyImportsPass);
   registerPass("minify-imports-and-exports", "minifies both import and export names, and emits a mapping to the minified ones", createMinifyImportsAndExportsPass);
   registerPass("nm", "name list", createNameListPass);
+  registerPass("no-exit-runtime", "removes calls to atexit(), which is valid if the C runtime will never be exited", createNoExitRuntimePass);
   registerPass("optimize-instructions", "optimizes instruction combinations", createOptimizeInstructionsPass);
   registerPass("optimize-stack-ir", "optimize Stack IR", createOptimizeStackIRPass);
   registerPass("pick-load-signs", "pick load signs based on their uses", createPickLoadSignsPass);
diff --git a/src/passes/passes.h b/src/passes/passes.h
index 8f5ca7e0a..df4322eee 100644
--- a/src/passes/passes.h
+++ b/src/passes/passes.h
@@ -55,6 +55,7 @@ Pass* createMinifyImportsPass();
 Pass* createMinifyImportsAndExportsPass();
 Pass* createMetricsPass();
 Pass* createNameListPass();
+Pass* createNoExitRuntimePass();
 Pass* createOptimizeInstructionsPass();
 Pass* createOptimizeStackIRPass();
 Pass* createPickLoadSignsPass();
diff --git a/test/passes/no-exit-runtime.txt b/test/passes/no-exit-runtime.txt
new file mode 100644
index 000000000..c8913d32a
--- /dev/null
+++ b/test/passes/no-exit-runtime.txt
@@ -0,0 +1,32 @@
+(module
+ (type $FUNCSIG$iii (func (param i32 i32) (result i32)))
+ (type $1 (func))
+ (import "env" "atexit" (func $fimport$0 (param i32 i32) (result i32)))
+ (import "env" "__cxa_atexit" (func $fimport$1 (param i32 i32) (result i32)))
+ (import "env" "_atexit" (func $fimport$2 (param i32 i32) (result i32)))
+ (import "env" "___cxa_atexit" (func $fimport$3 (param i32 i32) (result i32)))
+ (import "env" "other" (func $fimport$4 (param i32 i32) (result i32)))
+ (func $caller (; 5 ;) (type $1)
+  (drop
+   (i32.const 0)
+  )
+  (drop
+   (i32.const 0)
+  )
+  (drop
+   (i32.const 0)
+  )
+  (drop
+   (i32.const 0)
+  )
+  (drop
+   (call $fimport$4
+    (i32.const 0)
+    (i32.const 1)
+   )
+  )
+  (drop
+   (unreachable)
+  )
+ )
+)
diff --git a/test/passes/no-exit-runtime.wast b/test/passes/no-exit-runtime.wast
new file mode 100644
index 000000000..1afe5ef8d
--- /dev/null
+++ b/test/passes/no-exit-runtime.wast
@@ -0,0 +1,15 @@
+(module
+  (import "env" "atexit" (func $fimport$0 (param i32 i32) (result i32)))
+  (import "env" "__cxa_atexit" (func $fimport$1 (param i32 i32) (result i32)))
+  (import "env" "_atexit" (func $fimport$2 (param i32 i32) (result i32)))
+  (import "env" "___cxa_atexit" (func $fimport$3 (param i32 i32) (result i32)))
+  (import "env" "other" (func $fimport$4 (param i32 i32) (result i32)))
+  (func $caller
+    (drop (call $fimport$0 (i32.const 0) (i32.const 1)))
+    (drop (call $fimport$1 (i32.const 0) (i32.const 1)))
+    (drop (call $fimport$2 (i32.const 0) (i32.const 1)))
+    (drop (call $fimport$3 (i32.const 0) (i32.const 1)))
+    (drop (call $fimport$4 (i32.const 0) (i32.const 1)))
+    (drop (call $fimport$0 (unreachable) (i32.const 1)))
+  )
+)