Fuzzer: Add support to --fuzz-exec two files (WebAssembly#7947)

fuzz_shell.js already allows linking in a second file from JS. This does the same for
wasm-opt's --fuzz-exec-before functionality.

To do that, track linked instances in execution results, and link and run
a second module there, if provided.

Author: kripken

src/shell-interface.h

@@ -105,8 +105,8 @@ struct ShellExternalInterface : ModuleRunner::ExternalInterface {
   ModuleRunner* getImportInstance(Importable* import) {
     auto it = linkedInstances.find(import->module);
     if (it == linkedInstances.end()) {
-      Fatal() << "importGlobals: unknown import: " << import->module.str << "."
-              << import->base.str;
+      Fatal() << "getImportInstance: unknown import: " << import->module.str
+              << "." << import->base.str;
     }
     return it->second.get();
   }

src/tools/execution-results.h

@@ -55,8 +55,11 @@ struct LoggingExternalInterface : public ShellExternalInterface {
   ModuleRunner* instance = nullptr;
 
 public:
-  LoggingExternalInterface(Loggings& loggings, Module& wasm)
-    : loggings(loggings), wasm(wasm) {
+  LoggingExternalInterface(
+    Loggings& loggings,
+    Module& wasm,
+    std::map<Name, std::shared_ptr<ModuleRunner>> linkedInstances_ = {})
+    : ShellExternalInterface(linkedInstances_), loggings(loggings), wasm(wasm) {
     for (auto& exp : wasm.exports) {
       if (exp->kind == ExternalKind::Table && exp->name == "table") {
         exportedTable = *exp->getInternalName();
@@ -185,7 +188,11 @@ struct LoggingExternalInterface : public ShellExternalInterface {
       } else if (import->base == "getTempRet0") {
         return {Literal(state.tempRet0)};
       }
+    } else if (linkedInstances.count(import->module)) {
+      // This is from a recognized module.
+      return getImportInstance(import)->callExport(import->base, arguments);
     }
+    // Anything else, we ignore.
     std::cerr << "[LoggingExternalInterface ignoring an unknown import "
               << import->module << " . " << import->base << '\n';
     return {};
@@ -279,35 +286,24 @@ struct ExecutionResults {
   // If set, we should ignore this and not compare it to anything.
   bool ignore = false;
 
-  // get results of execution
-  void get(Module& wasm) {
-    LoggingExternalInterface interface(loggings, wasm);
+  // Get results of executing a module. Optionally, provide a second module to
+  // link with it (like fuzz_shell's second module).
+  void get(Module& wasm, Module* second = nullptr) {
     try {
-      ModuleRunner instance(wasm, &interface);
-      // This is not an optimization: we want to execute anything, even relaxed
-      // SIMD instructions.
-      instance.setRelaxedBehavior(ModuleRunner::RelaxedBehavior::Execute);
-      instance.instantiate();
-      interface.setModuleRunner(&instance);
-      // execute all exported methods (that are therefore preserved through
-      // opts)
-      for (auto& exp : wasm.exports) {
-        if (exp->kind != ExternalKind::Function) {
-          continue;
-        }
-        std::cout << "[fuzz-exec] calling " << exp->name << "\n";
-        auto* func = wasm.getFunction(*exp->getInternalName());
-        FunctionResult ret = run(func, wasm, instance);
-        results[exp->name] = ret;
-        if (auto* values = std::get_if<Literals>(&ret)) {
-          // ignore the result if we hit an unreachable and returned no value
-          if (values->size() > 0) {
-            std::cout << "[fuzz-exec] note result: " << exp->name << " => ";
-            for (auto value : *values) {
-              printValue(value);
-            }
-          }
-        }
+      // Run the first module.
+      LoggingExternalInterface interface(loggings, wasm);
+      auto instance = std::make_shared<ModuleRunner>(wasm, &interface);
+      runModule(wasm, *instance, interface);
+
+      if (second) {
+        // Link and run the second module.
+        std::map<Name, std::shared_ptr<ModuleRunner>> linkedInstances;
+        linkedInstances["primary"] = instance;
+        LoggingExternalInterface secondInterface(
+          loggings, *second, linkedInstances);
+        auto secondInstance = std::make_shared<ModuleRunner>(
+          *second, &secondInterface, linkedInstances);
+        runModule(*second, *secondInstance, secondInterface);
       }
     } catch (const TrapException&) {
       // May throw in instance creation (init of offsets).
@@ -319,6 +315,36 @@ struct ExecutionResults {
     }
   }
 
+  void runModule(Module& wasm,
+                 ModuleRunner& instance,
+                 LoggingExternalInterface& interface) {
+    // This is not an optimization: we want to execute anything, even relaxed
+    // SIMD instructions.
+    instance.setRelaxedBehavior(ModuleRunner::RelaxedBehavior::Execute);
+    instance.instantiate();
+    interface.setModuleRunner(&instance);
+    // execute all exported methods (that are therefore preserved through
+    // opts)
+    for (auto& exp : wasm.exports) {
+      if (exp->kind != ExternalKind::Function) {
+        continue;
+      }
+      std::cout << "[fuzz-exec] calling " << exp->name << "\n";
+      auto* func = wasm.getFunction(*exp->getInternalName());
+      FunctionResult ret = run(func, wasm, instance);
+      results[exp->name] = ret;
+      if (auto* values = std::get_if<Literals>(&ret)) {
+        // ignore the result if we hit an unreachable and returned no value
+        if (values->size() > 0) {
+          std::cout << "[fuzz-exec] note result: " << exp->name << " => ";
+          for (auto value : *values) {
+            printValue(value);
+          }
+        }
+      }
+    }
+  }
+
   void printValue(Literal value) {
     // Unwrap an externalized GC value to get the actual value, but not strings,
     // which are normally a subtype of ext.

src/tools/wasm-opt.cpp

@@ -79,6 +79,7 @@ int main(int argc, const char* argv[]) {
   bool converge = false;
   bool fuzzExecBefore = false;
   bool fuzzExecAfter = false;
+  std::string fuzzExecSecond;
   std::string extraFuzzCommand;
   bool translateToFuzz = false;
   std::string initialFuzz;
@@ -148,6 +149,15 @@ For more on how to optimize effectively, see
          [&](Options* o, const std::string& arguments) {
            fuzzExecBefore = fuzzExecAfter = true;
          })
+    .add("--fuzz-exec-second",
+         "",
+         "A second module to link with the first, for fuzz-exec-before (only "
+         "before, as optimizations are not applied to it)",
+         WasmOptOption,
+         Options::Arguments::One,
+         [&](Options* o, const std::string& arguments) {
+           fuzzExecSecond = arguments;
+         })
     .add("--extra-fuzz-command",
          "-efc",
          "An extra command to run on the output before and after optimizing. "
@@ -345,7 +355,16 @@ For more on how to optimize effectively, see
 
   ExecutionResults results;
   if (fuzzExecBefore) {
-    results.get(wasm);
+    if (fuzzExecSecond.empty()) {
+      results.get(wasm);
+    } else {
+      // Add the second module.
+      Module second;
+      second.features = wasm.features;
+      ModuleReader().read(fuzzExecSecond, second);
+
+      results.get(wasm, &second);
+    }
   }
 
   if (emitSpecWrapper.size() > 0) {

test/lit/exec/second.wast

@@ -0,0 +1,17 @@
+
+;; RUN: wasm-opt %s -all --fuzz-exec-before --fuzz-exec-second=%s.second -q -o /dev/null 2>&1 | filecheck %s
+
+(module
+  (func $first (export "first") (result i32)
+    (i32.const 42)
+  )
+)
+
+;; Test that --fuzz-exec-second will run a second wasm file that is
+;; provided, and call its exports as well as the first module's.
+
+;; CHECK:      [fuzz-exec] calling first
+;; CHECK-NEXT: [fuzz-exec] note result: first => 42
+;; CHECK:      [fuzz-exec] calling second
+;; CHECK-NEXT: [fuzz-exec] note result: second => 1337
+

test/lit/exec/second.wast.second

@@ -0,0 +1,12 @@
+(module
+  (import "primary" "first" (func $first-func (result i32)))
+
+  (func $second (export "second") (result i32)
+    ;; Test we can call the first module, linked as "primary."
+    (i32.add
+      (call $first-func)
+      (i32.const 1295)
+    )
+  )
+)
+

test/lit/help/wasm-opt.test

@@ -38,6 +38,11 @@
 ;; CHECK-NEXT:                                                 after optimization, helping
 ;; CHECK-NEXT:                                                 fuzzing find bugs
 ;; CHECK-NEXT:
+;; CHECK-NEXT:   --fuzz-exec-second                            A second module to link with the
+;; CHECK-NEXT:                                                 first, for fuzz-exec-before
+;; CHECK-NEXT:                                                 (only before, as optimizations
+;; CHECK-NEXT:                                                 are not applied to it)
+;; CHECK-NEXT:
 ;; CHECK-NEXT:   --extra-fuzz-command,-efc                     An extra command to run on the
 ;; CHECK-NEXT:                                                 output before and after
 ;; CHECK-NEXT:                                                 optimizing. The output is