Imported Upstream version 5.18.0.167

Former-commit-id: 289509151e0fee68a1b591a20c9f109c3c789d3a

external/llvm/lib/Target/WebAssembly/WebAssemblyPrepareForLiveIntervals.cpp

@@ -1,124 +0,0 @@
-//===- WebAssemblyPrepareForLiveIntervals.cpp - Prepare for LiveIntervals -===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-///
-/// \file
-/// \brief Fix up code to meet LiveInterval's requirements.
-///
-/// Some CodeGen passes don't preserve LiveInterval's requirements, because
-/// they run after register allocation and it isn't important. However,
-/// WebAssembly runs LiveIntervals in a late pass. This pass transforms code
-/// to meet LiveIntervals' requirements; primarily, it ensures that all
-/// virtual register uses have definitions (IMPLICIT_DEF definitions if
-/// nothing else).
-///
-//===----------------------------------------------------------------------===//
-
-#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
-#include "WebAssembly.h"
-#include "WebAssemblyMachineFunctionInfo.h"
-#include "WebAssemblySubtarget.h"
-#include "WebAssemblyUtilities.h"
-#include "llvm/CodeGen/MachineFunctionPass.h"
-#include "llvm/CodeGen/MachineInstrBuilder.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-prepare-for-live-intervals"
-
-namespace {
-class WebAssemblyPrepareForLiveIntervals final : public MachineFunctionPass {
-public:
-  static char ID; // Pass identification, replacement for typeid
-  WebAssemblyPrepareForLiveIntervals() : MachineFunctionPass(ID) {}
-
-private:
-  StringRef getPassName() const override {
-    return "WebAssembly Prepare For LiveIntervals";
-  }
-
-  void getAnalysisUsage(AnalysisUsage &AU) const override {
-    AU.setPreservesCFG();
-    MachineFunctionPass::getAnalysisUsage(AU);
-  }
-
-  bool runOnMachineFunction(MachineFunction &MF) override;
-};
-} // end anonymous namespace
-
-char WebAssemblyPrepareForLiveIntervals::ID = 0;
-FunctionPass *llvm::createWebAssemblyPrepareForLiveIntervals() {
-  return new WebAssemblyPrepareForLiveIntervals();
-}
-
-// Test whether the given register has an ARGUMENT def.
-static bool HasArgumentDef(unsigned Reg, const MachineRegisterInfo &MRI) {
-  for (const auto &Def : MRI.def_instructions(Reg))
-    if (WebAssembly::isArgument(Def))
-      return true;
-  return false;
-}
-
-bool WebAssemblyPrepareForLiveIntervals::runOnMachineFunction(MachineFunction &MF) {
-  DEBUG({
-    dbgs() << "********** Prepare For LiveIntervals **********\n"
-           << "********** Function: " << MF.getName() << '\n';
-  });
-
-  bool Changed = false;
-  MachineRegisterInfo &MRI = MF.getRegInfo();
-  const auto &TII = *MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
-  MachineBasicBlock &Entry = *MF.begin();
-
-  assert(!mustPreserveAnalysisID(LiveIntervalsID) &&
-         "LiveIntervals shouldn't be active yet!");
-
-  // We don't preserve SSA form.
-  MRI.leaveSSA();
-
-  // BranchFolding and perhaps other passes don't preserve IMPLICIT_DEF
-  // instructions. LiveIntervals requires that all paths to virtual register
-  // uses provide a definition. Insert IMPLICIT_DEFs in the entry block to
-  // conservatively satisfy this.
-  //
-  // TODO: This is fairly heavy-handed; find a better approach.
-  //
-  for (unsigned i = 0, e = MRI.getNumVirtRegs(); i < e; ++i) {
-    unsigned Reg = TargetRegisterInfo::index2VirtReg(i);
-
-    // Skip unused registers.
-    if (MRI.use_nodbg_empty(Reg))
-      continue;
-
-    // Skip registers that have an ARGUMENT definition.
-    if (HasArgumentDef(Reg, MRI))
-      continue;
-
-    BuildMI(Entry, Entry.begin(), DebugLoc(),
-            TII.get(WebAssembly::IMPLICIT_DEF), Reg);
-    Changed = true;
-  }
-
-  // Move ARGUMENT_* instructions to the top of the entry block, so that their
-  // liveness reflects the fact that these really are live-in values.
-  for (auto MII = Entry.begin(), MIE = Entry.end(); MII != MIE; ) {
-    MachineInstr &MI = *MII++;
-    if (WebAssembly::isArgument(MI)) {
-      MI.removeFromParent();
-      Entry.insert(Entry.begin(), &MI);
-    }
-  }
-
-  // Ok, we're now ready to run the LiveIntervals analysis again.
-  MF.getProperties().set(MachineFunctionProperties::Property::TracksLiveness);
-
-  return Changed;
-}