[WebAssembly] Reapply r252858, with svn add for the new file.

Switch to MC for instruction printing.

This encompasses several changes which are all interconnected:
 - Use the MC framework for printing almost all instructions.
 - AsmStrings are now live.
 - This introduces an indirection between LLVM vregs and WebAssembly registers,
   and a new pass, WebAssemblyRegNumbering, for computing a basic the mapping.
   This addresses some basic issues with argument registers and unused registers.
 - The way ARGUMENT instructions are handled no longer generates redundant
   get_local+set_local for every argument.

This also changes the assembly syntax somewhat; most notably, MC's printing
does not use sigils on label names, so those are no longer present, and
push/pop now have a sigil to keep them unambiguous.

The usage of set_local/get_local/$push/$pop will continue to evolve
significantly. This patch is just one step of a larger change.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252910 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 98 insertions, 0 deletions

diff --git a/lib/Target/WebAssembly/WebAssemblyRegNumbering.cpp b/lib/Target/WebAssembly/WebAssemblyRegNumbering.cpp
new file mode 100644
index 00000000000..96b0799d1c3
--- /dev/null
+++ b/lib/Target/WebAssembly/WebAssemblyRegNumbering.cpp
@@ -0,0 +1,98 @@
+//===-- WebAssemblyRegNumbering.cpp - Register Numbering ------------------===//
+//
+//                     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 implements a pass which assigns WebAssembly register
+/// numbers for CodeGen virtual registers.
+///
+//===----------------------------------------------------------------------===//
+
+#include "WebAssembly.h"
+#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
+#include "WebAssemblyMachineFunctionInfo.h"
+#include "WebAssemblySubtarget.h"
+#include "llvm/ADT/SCCIterator.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineLoopInfo.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-reg-numbering"
+
+namespace {
+class WebAssemblyRegNumbering final : public MachineFunctionPass {
+  const char *getPassName() const override {
+    return "WebAssembly Register Numbering";
+  }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesCFG();
+    MachineFunctionPass::getAnalysisUsage(AU);
+  }
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+public:
+  static char ID; // Pass identification, replacement for typeid
+  WebAssemblyRegNumbering() : MachineFunctionPass(ID) {}
+};
+} // end anonymous namespace
+
+char WebAssemblyRegNumbering::ID = 0;
+FunctionPass *llvm::createWebAssemblyRegNumbering() {
+  return new WebAssemblyRegNumbering();
+}
+
+bool WebAssemblyRegNumbering::runOnMachineFunction(MachineFunction &MF) {
+  DEBUG(dbgs() << "********** Register Numbering **********\n"
+                  "********** Function: "
+               << MF.getName() << '\n');
+
+  WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>();
+  MachineRegisterInfo &MRI = MF.getRegInfo();
+
+  MFI.initWARegs();
+
+  // WebAssembly argument registers are in the same index space as local
+  // variables. Assign the numbers for them first.
+  for (MachineBasicBlock &MBB : MF) {
+    for (MachineInstr &MI : MBB) {
+      switch (MI.getOpcode()) {
+      case WebAssembly::ARGUMENT_I32:
+      case WebAssembly::ARGUMENT_I64:
+      case WebAssembly::ARGUMENT_F32:
+      case WebAssembly::ARGUMENT_F64:
+        MFI.setWAReg(MI.getOperand(0).getReg(), MI.getOperand(1).getImm());
+        break;
+      default:
+        break;
+      }
+    }
+  }
+
+  // Then assign regular WebAssembly registers for all remaining used
+  // virtual registers.
+  unsigned NumArgRegs = MFI.getParams().size();
+  unsigned NumVRegs = MF.getRegInfo().getNumVirtRegs();
+  unsigned CurReg = 0;
+  for (unsigned VRegIdx = 0; VRegIdx < NumVRegs; ++VRegIdx) {
+    unsigned VReg = TargetRegisterInfo::index2VirtReg(VRegIdx);
+    // Skip unused registers.
+    if (MRI.use_empty(VReg))
+      continue;
+    if (MFI.getWAReg(VReg) == -1u)
+      MFI.setWAReg(VReg, NumArgRegs + CurReg++);
+  }
+
+  return true;
+}