1 files changed, 76 insertions, 0 deletions

diff --git a/lib/Target/WebAssembly/WebAssemblyOptimizeReturned.cpp b/lib/Target/WebAssembly/WebAssemblyOptimizeReturned.cpp
new file mode 100644
index 000000000000..4dc401a2c7cc
--- /dev/null
+++ b/lib/Target/WebAssembly/WebAssemblyOptimizeReturned.cpp
@@ -0,0 +1,76 @@
+//===-- WebAssemblyOptimizeReturned.cpp - Optimize "returned" attributes --===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief Optimize calls with "returned" attributes for WebAssembly.
+///
+//===----------------------------------------------------------------------===//
+
+#include "WebAssembly.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/InstVisitor.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "wasm-optimize-returned"
+
+namespace {
+class OptimizeReturned final : public FunctionPass,
+                               public InstVisitor<OptimizeReturned> {
+  const char *getPassName() const override {
+    return "WebAssembly Optimize Returned";
+  }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesCFG();
+    AU.addRequired<DominatorTreeWrapperPass>();
+    AU.addPreserved<DominatorTreeWrapperPass>();
+    FunctionPass::getAnalysisUsage(AU);
+  }
+
+  bool runOnFunction(Function &F) override;
+
+  DominatorTree *DT;
+
+public:
+  static char ID;
+  OptimizeReturned() : FunctionPass(ID), DT(nullptr) {}
+
+  void visitCallSite(CallSite CS);
+};
+} // End anonymous namespace
+
+char OptimizeReturned::ID = 0;
+FunctionPass *llvm::createWebAssemblyOptimizeReturned() {
+  return new OptimizeReturned();
+}
+
+void OptimizeReturned::visitCallSite(CallSite CS) {
+  for (unsigned i = 0, e = CS.getNumArgOperands(); i < e; ++i)
+    if (CS.paramHasAttr(1 + i, Attribute::Returned)) {
+      Instruction *Inst = CS.getInstruction();
+      Value *Arg = CS.getArgOperand(i);
+      // Ignore constants, globals, undef, etc.
+      if (isa<Constant>(Arg))
+        continue;
+      // Like replaceDominatedUsesWith but using Instruction/Use dominance.
+      for (auto UI = Arg->use_begin(), UE = Arg->use_end(); UI != UE;) {
+        Use &U = *UI++;
+        if (DT->dominates(Inst, U))
+          U.set(Inst);
+      }
+    }
+}
+
+bool OptimizeReturned::runOnFunction(Function &F) {
+  DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+  visit(F);
+  return true;
+}