2 files changed, 89 insertions, 92 deletions

diff --git a/llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp b/llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp
index 97318a8057b..ea43db0f413 100644
--- a/llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp
@@ -674,86 +674,94 @@ unsigned HexagonInstrInfo::insertBranch(MachineBasicBlock &MBB,
   return 2;
 }
 
-/// Analyze the loop code to find the loop induction variable and compare used
-/// to compute the number of iterations. Currently, we analyze loop that are
-/// controlled using hardware loops.  In this case, the induction variable
-/// instruction is null.  For all other cases, this function returns true, which
-/// means we're unable to analyze it.
-bool HexagonInstrInfo::analyzeLoop(MachineLoop &L,
-                                   MachineInstr *&IndVarInst,
-                                   MachineInstr *&CmpInst) const {
-
-  MachineBasicBlock *LoopEnd = L.getBottomBlock();
-  MachineBasicBlock::iterator I = LoopEnd->getFirstTerminator();
-  // We really "analyze" only hardware loops right now.
-  if (I != LoopEnd->end() && isEndLoopN(I->getOpcode())) {
-    IndVarInst = nullptr;
-    CmpInst = &*I;
-    return false;
+class HexagonPipelinerLoopInfo : public TargetInstrInfo::PipelinerLoopInfo {
+  MachineInstr *Loop, *EndLoop;
+  MachineFunction *MF;
+  const HexagonInstrInfo *TII;
+  int64_t TripCount;
+  Register LoopCount;
+  DebugLoc DL;
+
+public:
+  HexagonPipelinerLoopInfo(MachineInstr *Loop, MachineInstr *EndLoop)
+      : Loop(Loop), EndLoop(EndLoop), MF(Loop->getParent()->getParent()),
+        TII(MF->getSubtarget<HexagonSubtarget>().getInstrInfo()),
+        DL(Loop->getDebugLoc()) {
+    // Inspect the Loop instruction up-front, as it may be deleted when we call
+    // createTripCountGreaterCondition.
+    TripCount = Loop->getOpcode() == Hexagon::J2_loop0r
+                    ? -1
+                    : Loop->getOperand(1).getImm();
+    if (TripCount == -1)
+      LoopCount = Loop->getOperand(1).getReg();
   }
-  return true;
-}
 
-/// Generate code to reduce the loop iteration by one and check if the loop is
-/// finished. Return the value/register of the new loop count. this function
-/// assumes the nth iteration is peeled first.
-unsigned HexagonInstrInfo::reduceLoopCount(
-    MachineBasicBlock &MBB, MachineBasicBlock &PreHeader, MachineInstr *IndVar,
-    MachineInstr &Cmp, SmallVectorImpl<MachineOperand> &Cond,
-    SmallVectorImpl<MachineInstr *> &PrevInsts, unsigned Iter,
-    unsigned MaxIter) const {
-  // We expect a hardware loop currently. This means that IndVar is set
-  // to null, and the compare is the ENDLOOP instruction.
-  assert((!IndVar) && isEndLoopN(Cmp.getOpcode())
-                   && "Expecting a hardware loop");
-  MachineFunction *MF = MBB.getParent();
-  DebugLoc DL = Cmp.getDebugLoc();
-  SmallPtrSet<MachineBasicBlock *, 8> VisitedBBs;
-  MachineInstr *Loop = findLoopInstr(&MBB, Cmp.getOpcode(),
-                                     Cmp.getOperand(0).getMBB(), VisitedBBs);
-  if (!Loop)
-    return 0;
-  // If the loop trip count is a compile-time value, then just change the
-  // value.
-  if (Loop->getOpcode() == Hexagon::J2_loop0i ||
-      Loop->getOpcode() == Hexagon::J2_loop1i) {
-    int64_t Offset = Loop->getOperand(1).getImm();
-    if (Offset <= 1)
-      Loop->eraseFromParent();
-    else
-      Loop->getOperand(1).setImm(Offset - 1);
-    return Offset - 1;
+  bool shouldIgnoreForPipelining(const MachineInstr *MI) const override {
+    // Only ignore the terminator.
+    return MI == EndLoop;
   }
-  // The loop trip count is a run-time value. We generate code to subtract
-  // one from the trip count, and update the loop instruction.
-  assert(Loop->getOpcode() == Hexagon::J2_loop0r && "Unexpected instruction");
-  Register LoopCount = Loop->getOperand(1).getReg();
-  // Check if we're done with the loop.
-  unsigned LoopEnd = createVR(MF, MVT::i1);
-  MachineInstr *NewCmp = BuildMI(&MBB, DL, get(Hexagon::C2_cmpgtui), LoopEnd).
-    addReg(LoopCount).addImm(1);
-  unsigned NewLoopCount = createVR(MF, MVT::i32);
-  MachineInstr *NewAdd = BuildMI(&MBB, DL, get(Hexagon::A2_addi), NewLoopCount).
-    addReg(LoopCount).addImm(-1);
-  const HexagonRegisterInfo &HRI = *Subtarget.getRegisterInfo();
-  // Update the previously generated instructions with the new loop counter.
-  for (SmallVectorImpl<MachineInstr *>::iterator I = PrevInsts.begin(),
-         E = PrevInsts.end(); I != E; ++I)
-    (*I)->substituteRegister(LoopCount, NewLoopCount, 0, HRI);
-  PrevInsts.clear();
-  PrevInsts.push_back(NewCmp);
-  PrevInsts.push_back(NewAdd);
-  // Insert the new loop instruction if this is the last time the loop is
-  // decremented.
-  if (Iter == MaxIter)
-    BuildMI(&MBB, DL, get(Hexagon::J2_loop0r)).
-      addMBB(Loop->getOperand(0).getMBB()).addReg(NewLoopCount);
-  // Delete the old loop instruction.
-  if (Iter == 0)
-    Loop->eraseFromParent();
-  Cond.push_back(MachineOperand::CreateImm(Hexagon::J2_jumpf));
-  Cond.push_back(NewCmp->getOperand(0));
-  return NewLoopCount;
+
+  Optional<bool>
+  createTripCountGreaterCondition(int TC, MachineBasicBlock &MBB,
+                                  SmallVectorImpl<MachineOperand> &Cond) override {
+    if (TripCount == -1) {
+      // Check if we're done with the loop.
+      unsigned Done = TII->createVR(MF, MVT::i1);
+      MachineInstr *NewCmp = BuildMI(&MBB, DL,
+                                     TII->get(Hexagon::C2_cmpgtui), Done)
+                                 .addReg(LoopCount)
+                                 .addImm(TC);
+      Cond.push_back(MachineOperand::CreateImm(Hexagon::J2_jumpf));
+      Cond.push_back(NewCmp->getOperand(0));
+      return {};
+    }
+
+    return TripCount > TC;
+  }
+
+  void setPreheader(MachineBasicBlock *NewPreheader) override {
+    NewPreheader->splice(NewPreheader->getFirstTerminator(), Loop->getParent(),
+                         Loop);
+  }
+
+  void adjustTripCount(int TripCountAdjust) override {
+    // If the loop trip count is a compile-time value, then just change the
+    // value.
+    if (Loop->getOpcode() == Hexagon::J2_loop0i ||
+        Loop->getOpcode() == Hexagon::J2_loop1i) {
+      int64_t TripCount = Loop->getOperand(1).getImm() + TripCountAdjust;
+      assert(TripCount > 0 && "Can't create an empty or negative loop!");
+      Loop->getOperand(1).setImm(TripCount);
+      return;
+    }
+
+    // The loop trip count is a run-time value. We generate code to subtract
+    // one from the trip count, and update the loop instruction.
+    Register LoopCount = Loop->getOperand(1).getReg();
+    Register NewLoopCount = TII->createVR(MF, MVT::i32);
+    BuildMI(*Loop->getParent(), Loop, Loop->getDebugLoc(),
+            TII->get(Hexagon::A2_addi), NewLoopCount)
+        .addReg(LoopCount)
+        .addImm(TripCountAdjust);
+    Loop->getOperand(1).setReg(NewLoopCount);
+  }
+
+  void disposed() override { Loop->eraseFromParent(); }
+};
+
+std::unique_ptr<TargetInstrInfo::PipelinerLoopInfo>
+HexagonInstrInfo::analyzeLoopForPipelining(MachineBasicBlock *LoopBB) const {
+  // We really "analyze" only hardware loops right now.
+  MachineBasicBlock::iterator I = LoopBB->getFirstTerminator();
+
+  if (I != LoopBB->end() && isEndLoopN(I->getOpcode())) {
+    SmallPtrSet<MachineBasicBlock *, 8> VisitedBBs;
+    MachineInstr *LoopInst = findLoopInstr(
+        LoopBB, I->getOpcode(), I->getOperand(0).getMBB(), VisitedBBs);
+    if (LoopInst)
+      return std::make_unique<HexagonPipelinerLoopInfo>(LoopInst, &*I);
+  }
+  return nullptr;
 }
 
 bool HexagonInstrInfo::isProfitableToIfCvt(MachineBasicBlock &MBB,
diff --git a/llvm/lib/Target/Hexagon/HexagonInstrInfo.h b/llvm/lib/Target/Hexagon/HexagonInstrInfo.h
index e0a999d0f4c..e863400480b 100644
--- a/llvm/lib/Target/Hexagon/HexagonInstrInfo.h
+++ b/llvm/lib/Target/Hexagon/HexagonInstrInfo.h
@@ -129,21 +129,10 @@ public:
                         const DebugLoc &DL,
                         int *BytesAdded = nullptr) const override;
 
-  /// Analyze the loop code, return true if it cannot be understood. Upon
-  /// success, this function returns false and returns information about the
-  /// induction variable and compare instruction used at the end.
-  bool analyzeLoop(MachineLoop &L, MachineInstr *&IndVarInst,
-                   MachineInstr *&CmpInst) const override;
-
-  /// Generate code to reduce the loop iteration by one and check if the loop
-  /// is finished.  Return the value/register of the new loop count.  We need
-  /// this function when peeling off one or more iterations of a loop. This
-  /// function assumes the nth iteration is peeled first.
-  unsigned reduceLoopCount(MachineBasicBlock &MBB, MachineBasicBlock &PreHeader,
-                           MachineInstr *IndVar, MachineInstr &Cmp,
-                           SmallVectorImpl<MachineOperand> &Cond,
-                           SmallVectorImpl<MachineInstr *> &PrevInsts,
-                           unsigned Iter, unsigned MaxIter) const override;
+  /// Analyze loop L, which must be a single-basic-block loop, and if the
+  /// conditions can be understood enough produce a PipelinerLoopInfo object.
+  std::unique_ptr<PipelinerLoopInfo>
+  analyzeLoopForPipelining(MachineBasicBlock *LoopBB) const override;
 
   /// Return true if it's profitable to predicate
   /// instructions with accumulated instruction latency of "NumCycles"