Index: llvm/trunk/lib/Target/WebAssembly/CMakeLists.txt
===================================================================
--- llvm/trunk/lib/Target/WebAssembly/CMakeLists.txt
+++ llvm/trunk/lib/Target/WebAssembly/CMakeLists.txt
@@ -11,6 +11,7 @@
 
 add_llvm_target(WebAssemblyCodeGen
   Relooper.cpp
+  WebAssemblyArgumentMove.cpp
   WebAssemblyAsmPrinter.cpp
   WebAssemblyCFGStackify.cpp
   WebAssemblyFastISel.cpp
Index: llvm/trunk/lib/Target/WebAssembly/WebAssembly.h
===================================================================
--- llvm/trunk/lib/Target/WebAssembly/WebAssembly.h
+++ llvm/trunk/lib/Target/WebAssembly/WebAssembly.h
@@ -27,6 +27,7 @@
 
 FunctionPass *createWebAssemblyISelDag(WebAssemblyTargetMachine &TM,
                                        CodeGenOpt::Level OptLevel);
+FunctionPass *createWebAssemblyArgumentMove();
 
 FunctionPass *createWebAssemblyStoreResults();
 FunctionPass *createWebAssemblyRegStackify();
Index: llvm/trunk/lib/Target/WebAssembly/WebAssemblyArgumentMove.cpp
===================================================================
--- llvm/trunk/lib/Target/WebAssembly/WebAssemblyArgumentMove.cpp
+++ llvm/trunk/lib/Target/WebAssembly/WebAssemblyArgumentMove.cpp
@@ -0,0 +1,110 @@
+//===-- WebAssemblyArgumentMove.cpp - Argument instruction moving ---------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief This file moves ARGUMENT instructions after ScheduleDAG scheduling.
+///
+/// Arguments are really live-in registers, however, since we use virtual
+/// registers and LLVM doesn't support live-in virtual registers, we're
+/// currently making do with ARGUMENT instructions which are placed at the top
+/// of the entry block. The trick is to get them to *stay* at the top of the
+/// entry block.
+///
+/// The ARGUMENTS physical register keeps these instructions pinned in place
+/// during liveness-aware CodeGen passes, however one thing which does not
+/// respect this is the ScheduleDAG scheduler. This pass is therefore run
+/// immediately after that.
+///
+/// This is all hopefully a temporary solution until we find a better solution
+/// for describing the live-in nature of arguments.
+///
+//===----------------------------------------------------------------------===//
+
+#include "WebAssembly.h"
+#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
+#include "WebAssemblyMachineFunctionInfo.h"
+#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "wasm-argument-move"
+
+namespace {
+class WebAssemblyArgumentMove final : public MachineFunctionPass {
+public:
+  static char ID; // Pass identification, replacement for typeid
+  WebAssemblyArgumentMove() : MachineFunctionPass(ID) {}
+
+  const char *getPassName() const override {
+    return "WebAssembly Argument Move";
+  }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesCFG();
+    AU.addPreserved<MachineBlockFrequencyInfo>();
+    AU.addPreservedID(MachineDominatorsID);
+    MachineFunctionPass::getAnalysisUsage(AU);
+  }
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
+};
+} // end anonymous namespace
+
+char WebAssemblyArgumentMove::ID = 0;
+FunctionPass *llvm::createWebAssemblyArgumentMove() {
+  return new WebAssemblyArgumentMove();
+}
+
+/// Test whether the given instruction is an ARGUMENT.
+static bool IsArgument(const MachineInstr *MI) {
+  switch (MI->getOpcode()) {
+  case WebAssembly::ARGUMENT_I32:
+  case WebAssembly::ARGUMENT_I64:
+  case WebAssembly::ARGUMENT_F32:
+  case WebAssembly::ARGUMENT_F64:
+    return true;
+  default:
+    return false;
+  }
+}
+
+bool WebAssemblyArgumentMove::runOnMachineFunction(MachineFunction &MF) {
+  DEBUG({
+    dbgs() << "********** Argument Move **********\n"
+           << "********** Function: " << MF.getName() << '\n';
+  });
+
+  bool Changed = false;
+  MachineBasicBlock &EntryMBB = MF.front();
+  MachineBasicBlock::iterator InsertPt = EntryMBB.end();
+
+  // Look for the first NonArg instruction.
+  for (auto MII = EntryMBB.begin(), MIE = EntryMBB.end(); MII != MIE; ++MII) {
+    MachineInstr *MI = MII;
+    if (!IsArgument(MI)) {
+      InsertPt = MII;
+      break;
+    }
+  }
+
+  // Now move any argument instructions later in the block
+  // to before our first NonArg instruction.
+  for (auto I = InsertPt, E = EntryMBB.end(); I != E; ++I) {
+    MachineInstr *MI = I;
+    if (IsArgument(MI)) {
+      EntryMBB.insert(InsertPt, MI->removeFromParent());
+      Changed = true;
+    }
+  }
+
+  return Changed;
+}
Index: llvm/trunk/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
===================================================================
--- llvm/trunk/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
+++ llvm/trunk/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
@@ -149,6 +149,10 @@
   (void)TargetPassConfig::addInstSelector();
   addPass(
       createWebAssemblyISelDag(getWebAssemblyTargetMachine(), getOptLevel()));
+  // Run the argument-move pass immediately after the ScheduleDAG scheduler
+  // so that we can fix up the ARGUMENT instructions before anything else
+  // sees them in the wrong place.
+  addPass(createWebAssemblyArgumentMove());
   return false;
 }
 
Index: llvm/trunk/test/CodeGen/WebAssembly/dead-vreg.ll
===================================================================
--- llvm/trunk/test/CodeGen/WebAssembly/dead-vreg.ll
+++ llvm/trunk/test/CodeGen/WebAssembly/dead-vreg.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -asm-verbose=false | FileCheck %s
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs | FileCheck %s
 
 ; Check that unused vregs aren't assigned registers.
 
Index: llvm/trunk/test/CodeGen/WebAssembly/phi.ll
===================================================================
--- llvm/trunk/test/CodeGen/WebAssembly/phi.ll
+++ llvm/trunk/test/CodeGen/WebAssembly/phi.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -asm-verbose=false | FileCheck %s
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs | FileCheck %s
 
 ; Test that phis are lowered.
 
Index: llvm/trunk/test/CodeGen/WebAssembly/reg-stackify.ll
===================================================================
--- llvm/trunk/test/CodeGen/WebAssembly/reg-stackify.ll
+++ llvm/trunk/test/CodeGen/WebAssembly/reg-stackify.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -asm-verbose=false | FileCheck %s
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs | FileCheck %s
 
 ; Test the register stackifier pass.
 
Index: llvm/trunk/test/CodeGen/WebAssembly/switch.ll
===================================================================
--- llvm/trunk/test/CodeGen/WebAssembly/switch.ll
+++ llvm/trunk/test/CodeGen/WebAssembly/switch.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -asm-verbose=false -disable-block-placement | FileCheck %s
+; RUN: llc < %s -asm-verbose=false -disable-block-placement -verify-machineinstrs | FileCheck %s
 
 ; Test switch instructions. Block placement is disabled because it reorders
 ; the blocks in a way that isn't interesting here.
Index: llvm/trunk/test/CodeGen/WebAssembly/unreachable.ll
===================================================================
--- llvm/trunk/test/CodeGen/WebAssembly/unreachable.ll
+++ llvm/trunk/test/CodeGen/WebAssembly/unreachable.ll
@@ -1,5 +1,5 @@
-; RUN: llc < %s -asm-verbose=false | FileCheck %s
-; RUN: llc < %s -asm-verbose=false -fast-isel | FileCheck %s
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs | FileCheck %s
+; RUN: llc < %s -asm-verbose=false -fast-isel -verify-machineinstrs | FileCheck %s
 
 ; Test that LLVM unreachable instruction and trap intrinsic are lowered to
 ; wasm unreachable
Index: llvm/trunk/test/CodeGen/WebAssembly/varargs.ll
===================================================================
--- llvm/trunk/test/CodeGen/WebAssembly/varargs.ll
+++ llvm/trunk/test/CodeGen/WebAssembly/varargs.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -asm-verbose=false | FileCheck %s
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs | FileCheck %s
 
 ; Test varargs constructs.