1 files changed, 188 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Target/Hexagon/HexagonFixupHwLoops.cpp b/contrib/llvm/lib/Target/Hexagon/HexagonFixupHwLoops.cpp
new file mode 100644
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--- /dev/null
+++ b/contrib/llvm/lib/Target/Hexagon/HexagonFixupHwLoops.cpp
@@ -0,0 +1,188 @@
+//===---- HexagonFixupHwLoops.cpp - Fixup HW loops too far from LOOPn. ----===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+// The loop start address in the LOOPn instruction is encoded as a distance
+// from the LOOPn instruction itself. If the start address is too far from
+// the LOOPn instruction, the instruction needs to use a constant extender.
+// This pass will identify and convert such LOOPn instructions to a proper
+// form.
+//===----------------------------------------------------------------------===//
+
+
+#include "llvm/ADT/DenseMap.h"
+#include "Hexagon.h"
+#include "HexagonTargetMachine.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/PassSupport.h"
+#include "llvm/Target/TargetInstrInfo.h"
+
+using namespace llvm;
+
+static cl::opt<unsigned> MaxLoopRange(
+    "hexagon-loop-range", cl::Hidden, cl::init(200),
+    cl::desc("Restrict range of loopN instructions (testing only)"));
+
+namespace llvm {
+  FunctionPass *createHexagonFixupHwLoops();
+  void initializeHexagonFixupHwLoopsPass(PassRegistry&);
+}
+
+namespace {
+  struct HexagonFixupHwLoops : public MachineFunctionPass {
+  public:
+    static char ID;
+
+    HexagonFixupHwLoops() : MachineFunctionPass(ID) {
+      initializeHexagonFixupHwLoopsPass(*PassRegistry::getPassRegistry());
+    }
+
+    bool runOnMachineFunction(MachineFunction &MF) override;
+
+    const char *getPassName() const override {
+      return "Hexagon Hardware Loop Fixup";
+    }
+
+    void getAnalysisUsage(AnalysisUsage &AU) const override {
+      AU.setPreservesCFG();
+      MachineFunctionPass::getAnalysisUsage(AU);
+    }
+
+  private:
+    /// \brief Check the offset between each loop instruction and
+    /// the loop basic block to determine if we can use the LOOP instruction
+    /// or if we need to set the LC/SA registers explicitly.
+    bool fixupLoopInstrs(MachineFunction &MF);
+
+    /// \brief Replace loop instruction with the constant extended
+    /// version if the loop label is too far from the loop instruction.
+    void useExtLoopInstr(MachineFunction &MF,
+                         MachineBasicBlock::iterator &MII);
+  };
+
+  char HexagonFixupHwLoops::ID = 0;
+}
+
+INITIALIZE_PASS(HexagonFixupHwLoops, "hwloopsfixup",
+                "Hexagon Hardware Loops Fixup", false, false)
+
+FunctionPass *llvm::createHexagonFixupHwLoops() {
+  return new HexagonFixupHwLoops();
+}
+
+/// \brief Returns true if the instruction is a hardware loop instruction.
+static bool isHardwareLoop(const MachineInstr *MI) {
+  return MI->getOpcode() == Hexagon::J2_loop0r ||
+         MI->getOpcode() == Hexagon::J2_loop0i ||
+         MI->getOpcode() == Hexagon::J2_loop1r ||
+         MI->getOpcode() == Hexagon::J2_loop1i;
+}
+
+bool HexagonFixupHwLoops::runOnMachineFunction(MachineFunction &MF) {
+  return fixupLoopInstrs(MF);
+}
+
+/// \brief For Hexagon, if the loop label is to far from the
+/// loop instruction then we need to set the LC0 and SA0 registers
+/// explicitly instead of using LOOP(start,count).  This function
+/// checks the distance, and generates register assignments if needed.
+///
+/// This function makes two passes over the basic blocks.  The first
+/// pass computes the offset of the basic block from the start.
+/// The second pass checks all the loop instructions.
+bool HexagonFixupHwLoops::fixupLoopInstrs(MachineFunction &MF) {
+
+  // Offset of the current instruction from the start.
+  unsigned InstOffset = 0;
+  // Map for each basic block to it's first instruction.
+  DenseMap<const MachineBasicBlock *, unsigned> BlockToInstOffset;
+
+  const HexagonInstrInfo *HII =
+      static_cast<const HexagonInstrInfo *>(MF.getSubtarget().getInstrInfo());
+
+  // First pass - compute the offset of each basic block.
+  for (const MachineBasicBlock &MBB : MF) {
+    if (MBB.getAlignment()) {
+      // Although we don't know the exact layout of the final code, we need
+      // to account for alignment padding somehow. This heuristic pads each
+      // aligned basic block according to the alignment value.
+      int ByteAlign = (1u << MBB.getAlignment()) - 1;
+      InstOffset = (InstOffset + ByteAlign) & ~(ByteAlign);
+    }
+
+    BlockToInstOffset[&MBB] = InstOffset;
+    for (const MachineInstr &MI : MBB)
+      InstOffset += HII->getSize(&MI);
+  }
+
+  // Second pass - check each loop instruction to see if it needs to be
+  // converted.
+  InstOffset = 0;
+  bool Changed = false;
+  for (MachineBasicBlock &MBB : MF) {
+    InstOffset = BlockToInstOffset[&MBB];
+
+    // Loop over all the instructions.
+    MachineBasicBlock::iterator MII = MBB.begin();
+    MachineBasicBlock::iterator MIE = MBB.end();
+    while (MII != MIE) {
+      InstOffset += HII->getSize(&*MII);
+      if (MII->isDebugValue()) {
+        ++MII;
+        continue;
+      }
+      if (isHardwareLoop(MII)) {
+        assert(MII->getOperand(0).isMBB() &&
+               "Expect a basic block as loop operand");
+        int diff = InstOffset - BlockToInstOffset[MII->getOperand(0).getMBB()];
+        if ((unsigned)abs(diff) > MaxLoopRange) {
+          useExtLoopInstr(MF, MII);
+          MII = MBB.erase(MII);
+          Changed = true;
+        } else {
+          ++MII;
+        }
+      } else {
+        ++MII;
+      }
+    }
+  }
+
+  return Changed;
+}
+
+/// \brief Replace loop instructions with the constant extended version.
+void HexagonFixupHwLoops::useExtLoopInstr(MachineFunction &MF,
+                                          MachineBasicBlock::iterator &MII) {
+  const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
+  MachineBasicBlock *MBB = MII->getParent();
+  DebugLoc DL = MII->getDebugLoc();
+  MachineInstrBuilder MIB;
+  unsigned newOp;
+  switch (MII->getOpcode()) {
+  case Hexagon::J2_loop0r:
+    newOp = Hexagon::J2_loop0rext;
+    break;
+  case Hexagon::J2_loop0i:
+    newOp = Hexagon::J2_loop0iext;
+    break;
+  case Hexagon::J2_loop1r:
+    newOp = Hexagon::J2_loop1rext;
+    break;
+  case Hexagon::J2_loop1i:
+    newOp = Hexagon::J2_loop1iext;
+    break;
+  default:
+    llvm_unreachable("Invalid Hardware Loop Instruction.");
+  }
+  MIB = BuildMI(*MBB, MII, DL, TII->get(newOp));
+
+  for (unsigned i = 0; i < MII->getNumOperands(); ++i)
+    MIB.addOperand(MII->getOperand(i));
+}