1 files changed, 162 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Target/AArch64/AArch64CompressJumpTables.cpp b/contrib/llvm/lib/Target/AArch64/AArch64CompressJumpTables.cpp
new file mode 100644
index 000000000000..0924a27e2586
--- /dev/null
+++ b/contrib/llvm/lib/Target/AArch64/AArch64CompressJumpTables.cpp
@@ -0,0 +1,162 @@
+//==-- AArch64CompressJumpTables.cpp - Compress jump tables for AArch64 --====//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+// This pass looks at the basic blocks each jump-table refers to and works out
+// whether they can be emitted in a compressed form (with 8 or 16-bit
+// entries). If so, it changes the opcode and flags them in the associated
+// AArch64FunctionInfo.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AArch64.h"
+#include "AArch64MachineFunctionInfo.h"
+#include "AArch64Subtarget.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineJumpTableInfo.h"
+#include "llvm/CodeGen/TargetInstrInfo.h"
+#include "llvm/CodeGen/TargetSubtargetInfo.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/Support/Debug.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "aarch64-jump-tables"
+
+STATISTIC(NumJT8, "Number of jump-tables with 1-byte entries");
+STATISTIC(NumJT16, "Number of jump-tables with 2-byte entries");
+STATISTIC(NumJT32, "Number of jump-tables with 4-byte entries");
+
+namespace {
+class AArch64CompressJumpTables : public MachineFunctionPass {
+  const TargetInstrInfo *TII;
+  MachineFunction *MF;
+  SmallVector<int, 8> BlockInfo;
+
+  int computeBlockSize(MachineBasicBlock &MBB);
+  void scanFunction();
+
+  bool compressJumpTable(MachineInstr &MI, int Offset);
+
+public:
+  static char ID;
+  AArch64CompressJumpTables() : MachineFunctionPass(ID) {
+    initializeAArch64CompressJumpTablesPass(*PassRegistry::getPassRegistry());
+  }
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+  MachineFunctionProperties getRequiredProperties() const override {
+    return MachineFunctionProperties().set(
+        MachineFunctionProperties::Property::NoVRegs);
+  }
+  StringRef getPassName() const override {
+    return "AArch64 Compress Jump Tables";
+  }
+};
+char AArch64CompressJumpTables::ID = 0;
+}
+
+INITIALIZE_PASS(AArch64CompressJumpTables, DEBUG_TYPE,
+                "AArch64 compress jump tables pass", false, false)
+
+int AArch64CompressJumpTables::computeBlockSize(MachineBasicBlock &MBB) {
+  int Size = 0;
+  for (const MachineInstr &MI : MBB)
+    Size += TII->getInstSizeInBytes(MI);
+  return Size;
+}
+
+void AArch64CompressJumpTables::scanFunction() {
+  BlockInfo.clear();
+  BlockInfo.resize(MF->getNumBlockIDs());
+
+  int Offset = 0;
+  for (MachineBasicBlock &MBB : *MF) {
+    BlockInfo[MBB.getNumber()] = Offset;
+    Offset += computeBlockSize(MBB);
+  }
+}
+
+bool AArch64CompressJumpTables::compressJumpTable(MachineInstr &MI,
+                                                  int Offset) {
+  if (MI.getOpcode() != AArch64::JumpTableDest32)
+    return false;
+
+  int JTIdx = MI.getOperand(4).getIndex();
+  auto &JTInfo = *MF->getJumpTableInfo();
+  const MachineJumpTableEntry &JT = JTInfo.getJumpTables()[JTIdx];
+
+  // The jump-table might have been optimized away.
+  if (JT.MBBs.empty())
+    return false;
+
+  int MaxOffset = std::numeric_limits<int>::min(),
+      MinOffset = std::numeric_limits<int>::max();
+  MachineBasicBlock *MinBlock = nullptr;
+  for (auto Block : JT.MBBs) {
+    int BlockOffset = BlockInfo[Block->getNumber()];
+    assert(BlockOffset % 4 == 0 && "misaligned basic block");
+
+    MaxOffset = std::max(MaxOffset, BlockOffset);
+    if (BlockOffset <= MinOffset) {
+      MinOffset = BlockOffset;
+      MinBlock = Block;
+    }
+  }
+
+  // The ADR instruction needed to calculate the address of the first reachable
+  // basic block can address +/-1MB.
+  if (!isInt<21>(MinOffset - Offset)) {
+    ++NumJT32;
+    return false;
+  }
+
+  int Span = MaxOffset - MinOffset;
+  auto AFI = MF->getInfo<AArch64FunctionInfo>();
+  if (isUInt<8>(Span / 4)) {
+    AFI->setJumpTableEntryInfo(JTIdx, 1, MinBlock->getSymbol());
+    MI.setDesc(TII->get(AArch64::JumpTableDest8));
+    ++NumJT8;
+    return true;
+  } else if (isUInt<16>(Span / 4)) {
+    AFI->setJumpTableEntryInfo(JTIdx, 2, MinBlock->getSymbol());
+    MI.setDesc(TII->get(AArch64::JumpTableDest16));
+    ++NumJT16;
+    return true;
+  }
+
+  ++NumJT32;
+  return false;
+}
+
+bool AArch64CompressJumpTables::runOnMachineFunction(MachineFunction &MFIn) {
+  bool Changed = false;
+  MF = &MFIn;
+
+  const auto &ST = MF->getSubtarget<AArch64Subtarget>();
+  TII = ST.getInstrInfo();
+
+  if (ST.force32BitJumpTables() && !MF->getFunction().optForMinSize())
+    return false;
+
+  scanFunction();
+
+  for (MachineBasicBlock &MBB : *MF) {
+    int Offset = BlockInfo[MBB.getNumber()];
+    for (MachineInstr &MI : MBB) {
+      Changed |= compressJumpTable(MI, Offset);
+      Offset += TII->getInstSizeInBytes(MI);
+    }
+  }
+
+  return Changed;
+}
+
+FunctionPass *llvm::createAArch64CompressJumpTablesPass() {
+  return new AArch64CompressJumpTables();
+}