Separate LoopTraversal, ReachingDefAnalysis and BreakFalseDeps into their own files.

This is the one of multiple patches that fix bugzilla https://bugs.llvm.org/show_bug.cgi?id=33869
Most of the patches are intended at refactoring the existent code.

Additional relevant reviews:
https://reviews.llvm.org/D40330
https://reviews.llvm.org/D40331
https://reviews.llvm.org/D40332
https://reviews.llvm.org/D40334

Differential Revision: https://reviews.llvm.org/D40333

Change-Id: Ie5f8eb34d98cfdfae23a3072eb69b5794f0e2d56
llvm-svn: 323095

1 files changed, 195 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/ReachingDefAnalysis.cpp b/llvm/lib/CodeGen/ReachingDefAnalysis.cpp
new file mode 100644
index 00000000000..d24803a2186
--- /dev/null
+++ b/llvm/lib/CodeGen/ReachingDefAnalysis.cpp
@@ -0,0 +1,195 @@
+//===---- ReachingDefAnalysis.cpp - Reaching Def Analysis ---*- C++ -*-----===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/ReachingDefAnalysis.h"
+#include "llvm/CodeGen/TargetRegisterInfo.h"
+#include "llvm/CodeGen/TargetSubtargetInfo.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "reaching-deps-analysis"
+
+char ReachingDefAnalysis::ID = 0;
+INITIALIZE_PASS(ReachingDefAnalysis, DEBUG_TYPE, "ReachingDefAnalysis", false,
+                true)
+
+void ReachingDefAnalysis::enterBasicBlock(
+    const LoopTraversal::TraversedMBBInfo &TraversedMBB) {
+
+  MachineBasicBlock *MBB = TraversedMBB.MBB;
+  int MBBNumber = MBB->getNumber();
+  assert(MBBNumber < MBBReachingDefs.size() &&
+         "Unexpected basic block number.");
+  MBBReachingDefs[MBBNumber].resize(NumRegUnits);
+
+  // Reset instruction counter in each basic block.
+  CurInstr = 0;
+
+  // Set up LiveRegs to represent registers entering MBB.
+  // Default values are 'nothing happened a long time ago'.
+  if (LiveRegs.empty())
+    LiveRegs.assign(NumRegUnits, ReachingDedDefaultVal);
+
+  // This is the entry block.
+  if (MBB->pred_empty()) {
+    for (const auto &LI : MBB->liveins()) {
+      for (MCRegUnitIterator Unit(LI.PhysReg, TRI); Unit.isValid(); ++Unit) {
+        // Treat function live-ins as if they were defined just before the first
+        // instruction.  Usually, function arguments are set up immediately
+        // before the call.
+        LiveRegs[*Unit] = -1;
+        MBBReachingDefs[MBBNumber][*Unit].push_back(LiveRegs[*Unit]);
+      }
+    }
+    DEBUG(dbgs() << printMBBReference(*MBB) << ": entry\n");
+    return;
+  }
+
+  // Try to coalesce live-out registers from predecessors.
+  for (MachineBasicBlock *pred : MBB->predecessors()) {
+    assert(pred->getNumber() < MBBOutRegsInfos.size() &&
+           "Should have pre-allocated MBBInfos for all MBBs");
+    const LiveRegsDefInfo &Incoming = MBBOutRegsInfos[pred->getNumber()];
+    // Incoming is null if this is a backedge from a BB
+    // we haven't processed yet
+    if (Incoming.empty())
+      continue;
+
+    for (unsigned Unit = 0; Unit != NumRegUnits; ++Unit) {
+      // Use the most recent predecessor def for each register.
+      LiveRegs[Unit] = std::max(LiveRegs[Unit], Incoming[Unit]);
+      if ((LiveRegs[Unit] != ReachingDedDefaultVal))
+        MBBReachingDefs[MBBNumber][Unit].push_back(LiveRegs[Unit]);
+    }
+  }
+
+  DEBUG(dbgs() << printMBBReference(*MBB)
+               << (!TraversedMBB.IsDone ? ": incomplete\n"
+                                        : ": all preds known\n"));
+}
+
+void ReachingDefAnalysis::leaveBasicBlock(
+    const LoopTraversal::TraversedMBBInfo &TraversedMBB) {
+  assert(!LiveRegs.empty() && "Must enter basic block first.");
+  int MBBNumber = TraversedMBB.MBB->getNumber();
+  assert(MBBNumber < MBBOutRegsInfos.size() &&
+         "Unexpected basic block number.");
+  // Save register clearances at end of MBB - used by enterBasicBlock().
+  MBBOutRegsInfos[MBBNumber] = LiveRegs;
+
+  // While processing the basic block, we kept `Def` relative to the start
+  // of the basic block for convenience. However, future use of this information
+  // only cares about the clearance from the end of the block, so adjust
+  // everything to be relative to the end of the basic block.
+  for (int &OutLiveReg : MBBOutRegsInfos[MBBNumber])
+    OutLiveReg -= CurInstr;
+  LiveRegs.clear();
+}
+
+void ReachingDefAnalysis::processDefs(MachineInstr *MI) {
+  assert(!MI->isDebugValue() && "Won't process debug values");
+
+  int MBBNumber = MI->getParent()->getNumber();
+  assert(MBBNumber < MBBReachingDefs.size() &&
+         "Unexpected basic block number.");
+  const MCInstrDesc &MCID = MI->getDesc();
+  for (unsigned i = 0,
+                e = MI->isVariadic() ? MI->getNumOperands() : MCID.getNumDefs();
+       i != e; ++i) {
+    MachineOperand &MO = MI->getOperand(i);
+    if (!MO.isReg() || !MO.getReg())
+      continue;
+    if (MO.isUse())
+      continue;
+    for (MCRegUnitIterator Unit(MO.getReg(), TRI); Unit.isValid(); ++Unit) {
+      // This instruction explicitly defines the current reg unit.
+      DEBUG(dbgs() << printReg(MO.getReg(), TRI) << ":\t" << CurInstr << '\t'
+                   << *MI);
+
+      // How many instructions since this reg unit was last written?
+      LiveRegs[*Unit] = CurInstr;
+      MBBReachingDefs[MBBNumber][*Unit].push_back(CurInstr);
+    }
+  }
+  InstIds[MI] = CurInstr;
+  ++CurInstr;
+}
+
+void ReachingDefAnalysis::processBasicBlock(
+    const LoopTraversal::TraversedMBBInfo &TraversedMBB) {
+  enterBasicBlock(TraversedMBB);
+  for (MachineInstr &MI : *TraversedMBB.MBB) {
+    if (!MI.isDebugValue())
+      processDefs(&MI);
+  }
+  leaveBasicBlock(TraversedMBB);
+}
+
+bool ReachingDefAnalysis::runOnMachineFunction(MachineFunction &mf) {
+  if (skipFunction(mf.getFunction()))
+    return false;
+  MF = &mf;
+  TRI = MF->getSubtarget().getRegisterInfo();
+
+  LiveRegs.clear();
+  NumRegUnits = TRI->getNumRegUnits();
+
+  MBBReachingDefs.resize(mf.getNumBlockIDs());
+
+  DEBUG(dbgs() << "********** REACHING DEFINITION ANALYSIS **********\n");
+
+  // Initialize the MBBOutRegsInfos
+  MBBOutRegsInfos.resize(mf.getNumBlockIDs());
+
+  // Traverse the basic blocks.
+  LoopTraversal Traversal;
+  LoopTraversal::TraversalOrder TraversedMBBOrder = Traversal.traverse(mf);
+  for (LoopTraversal::TraversedMBBInfo TraversedMBB : TraversedMBBOrder) {
+    processBasicBlock(TraversedMBB);
+  }
+
+  // Sorting all reaching defs found for a ceartin reg unit in a given BB.
+  for (MBBDefsInfo &MBBDefs : MBBReachingDefs) {
+    for (MBBRegUnitDefs &RegUnitDefs : MBBDefs)
+      std::sort(RegUnitDefs.begin(), RegUnitDefs.end());
+  }
+
+  return false;
+}
+
+void ReachingDefAnalysis::releaseMemory() {
+  // Clear the internal vectors.
+  MBBOutRegsInfos.clear();
+  MBBReachingDefs.clear();
+  InstIds.clear();
+}
+
+int ReachingDefAnalysis::getReachingDef(MachineInstr *MI, int PhysReg) {
+  assert(InstIds.count(MI) && "Unexpected machine instuction.");
+  int InstId = InstIds[MI];
+  int DefRes = ReachingDedDefaultVal;
+  int MBBNumber = MI->getParent()->getNumber();
+  assert(MBBNumber < MBBReachingDefs.size() &&
+         "Unexpected basic block number.");
+  int LatestDef = ReachingDedDefaultVal;
+  for (MCRegUnitIterator Unit(PhysReg, TRI); Unit.isValid(); ++Unit) {
+    for (int Def : MBBReachingDefs[MBBNumber][*Unit]) {
+      if (Def >= InstId)
+        break;
+      DefRes = Def;
+    }
+    LatestDef = std::max(LatestDef, DefRes);
+  }
+  return LatestDef;
+}
+
+int ReachingDefAnalysis::getClearance(MachineInstr *MI, MCPhysReg PhysReg) {
+  assert(InstIds.count(MI) && "Unexpected machine instuction.");
+  return InstIds[MI] - getReachingDef(MI, PhysReg);
+}