--- /dev/null
+//===-- WebAssemblyAddMissingPrototypes.cpp - Fix prototypeless functions -===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Add prototypes to prototypes-less functions.
+///
+/// WebAssembly has strict function prototype checking so we need functions
+/// declarations to match the call sites. Clang treats prototype-less functions
+/// as varargs (foo(...)) which happens to work on existing platforms but
+/// doesn't under WebAssembly. This pass will find all the call sites of each
+/// prototype-less function, ensure they agree, and then set the signature
+/// on the function declaration accordingly.
+///
+//===----------------------------------------------------------------------===//
+
+#include "WebAssembly.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Operator.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/Debug.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "wasm-add-missing-prototypes"
+
+namespace {
+class WebAssemblyAddMissingPrototypes final : public ModulePass {
+ StringRef getPassName() const override {
+ return "Add prototypes to prototypes-less functions";
+ }
+
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
+ AU.setPreservesCFG();
+ ModulePass::getAnalysisUsage(AU);
+ }
+
+ bool runOnModule(Module &M) override;
+
+public:
+ static char ID;
+ WebAssemblyAddMissingPrototypes() : ModulePass(ID) {}
+};
+} // End anonymous namespace
+
+char WebAssemblyAddMissingPrototypes::ID = 0;
+INITIALIZE_PASS(WebAssemblyAddMissingPrototypes, DEBUG_TYPE,
+ "Add prototypes to prototypes-less functions", false, false)
+
+ModulePass *llvm::createWebAssemblyAddMissingPrototypes() {
+ return new WebAssemblyAddMissingPrototypes();
+}
+
+bool WebAssemblyAddMissingPrototypes::runOnModule(Module &M) {
+ LLVM_DEBUG(dbgs() << "runnning AddMissingPrototypes\n");
+
+ std::vector<std::pair<Function*, Function*>> Replacements;
+
+ // Find all the prototype-less function declarations
+ for (Function &F : M) {
+ if (!F.isDeclaration() || !F.hasFnAttribute("no-prototype"))
+ continue;
+
+ LLVM_DEBUG(dbgs() << "Found no-prototype function: " << F.getName() << "\n");
+
+ // When clang emits prototype-less C functions it uses (...), i.e. varargs
+ // function that take no arguments (have no sentinel). When we see a
+ // no-prototype attribute we expect the function have these properties.
+ if (!F.isVarArg())
+ report_fatal_error(
+ "Functions with 'no-prototype' attribute must take varargs: " +
+ F.getName());
+ if (F.getFunctionType()->getNumParams() != 0)
+ report_fatal_error(
+ "Functions with 'no-prototype' attribute should not have params: " +
+ F.getName());
+
+
+ // Create a function prototype based on the first call site (first bitcast)
+ // that we find.
+ FunctionType *NewType = nullptr;
+ Function* NewF = nullptr;
+ for (Use &U : F.uses()) {
+ LLVM_DEBUG(dbgs() << "prototype-less use: " << F.getName() << "\n");
+ if (BitCastOperator *BC = dyn_cast<BitCastOperator>(U.getUser())) {
+ FunctionType *DestType =
+ cast<FunctionType>(BC->getDestTy()->getPointerElementType());
+
+ // Create a new function with the correct type
+ NewType = DestType;
+ NewF = Function::Create(NewType, F.getLinkage(), F.getName());
+ NewF->setAttributes(F.getAttributes());
+ NewF->removeFnAttr("no-prototype");
+ break;
+ }
+ }
+
+ if (!NewType) {
+ LLVM_DEBUG(
+ dbgs() << "could not derive a function prototype from usage: " +
+ F.getName() + "\n");
+ continue;
+ }
+
+ for (Use &U : F.uses()) {
+ if (BitCastOperator *BC = dyn_cast<BitCastOperator>(U.getUser())) {
+ FunctionType *DestType =
+ cast<FunctionType>(BC->getDestTy()->getPointerElementType());
+ if (NewType != DestType) {
+ report_fatal_error(
+ "Prototypeless function used with conflicting signatures: " +
+ F.getName());
+ }
+ BC->replaceAllUsesWith(NewF);
+ Replacements.emplace_back(&F, NewF);
+ } else {
+ dbgs() << *U.getUser()->getType() << "\n";
+ U.getUser()->dump();
+ report_fatal_error(
+ "unexpected use of prototypeless function: " + F.getName() + "\n");
+ }
+ }
+ }
+
+ // Finally replace the old function declarations with the new ones
+ for (auto &Pair : Replacements) {
+ Function* Old = Pair.first;
+ Function* New = Pair.second;
+ Old->eraseFromParent();
+ M.getFunctionList().push_back(New);
+ }
+
+ return !Replacements.empty();
+}
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