diff options
Diffstat (limited to 'contrib/llvm/lib/Target/WebAssembly/WebAssemblyArgumentMove.cpp')
-rw-r--r-- | contrib/llvm/lib/Target/WebAssembly/WebAssemblyArgumentMove.cpp | 98 |
1 files changed, 98 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Target/WebAssembly/WebAssemblyArgumentMove.cpp b/contrib/llvm/lib/Target/WebAssembly/WebAssemblyArgumentMove.cpp new file mode 100644 index 000000000000..7c8a631cde8a --- /dev/null +++ b/contrib/llvm/lib/Target/WebAssembly/WebAssemblyArgumentMove.cpp @@ -0,0 +1,98 @@ +//===-- 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 +/// 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 "MCTargetDesc/WebAssemblyMCTargetDesc.h" +#include "WebAssembly.h" +#include "WebAssemblyMachineFunctionInfo.h" +#include "WebAssemblySubtarget.h" +#include "WebAssemblyUtilities.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) {} + + StringRef 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; +INITIALIZE_PASS(WebAssemblyArgumentMove, DEBUG_TYPE, + "Move ARGUMENT instructions for WebAssembly", false, false) + +FunctionPass *llvm::createWebAssemblyArgumentMove() { + return new WebAssemblyArgumentMove(); +} + +bool WebAssemblyArgumentMove::runOnMachineFunction(MachineFunction &MF) { + LLVM_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 (MachineInstr &MI : EntryMBB) { + if (!WebAssembly::isArgument(MI)) { + InsertPt = MI; + break; + } + } + + // Now move any argument instructions later in the block + // to before our first NonArg instruction. + for (MachineInstr &MI : llvm::make_range(InsertPt, EntryMBB.end())) { + if (WebAssembly::isArgument(MI)) { + EntryMBB.insert(InsertPt, MI.removeFromParent()); + Changed = true; + } + } + + return Changed; +} |