Rename SSEDomainFix -> lib/CodeGen/ExecutionDepsFix.

I'll clean up the source in the next commit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@140663 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 520 insertions, 0 deletions

diff --git a/lib/CodeGen/ExecutionDepsFix.cpp b/lib/CodeGen/ExecutionDepsFix.cpp
new file mode 100644
index 0000000000..8d8f5d452d
--- /dev/null
+++ b/lib/CodeGen/ExecutionDepsFix.cpp
@@ -0,0 +1,520 @@
+//===- SSEDomainFix.cpp - Use proper int/float domain for SSE ---*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains the SSEDomainFix pass.
+//
+// Some SSE instructions like mov, and, or, xor are available in different
+// variants for different operand types. These variant instructions are
+// equivalent, but on Nehalem and newer cpus there is extra latency
+// transferring data between integer and floating point domains.
+//
+// This pass changes the variant instructions to minimize domain crossings.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "execution-fix"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/Support/Allocator.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+using namespace llvm;
+
+/// A DomainValue is a bit like LiveIntervals' ValNo, but it also keeps track
+/// of execution domains.
+///
+/// An open DomainValue represents a set of instructions that can still switch
+/// execution domain. Multiple registers may refer to the same open
+/// DomainValue - they will eventually be collapsed to the same execution
+/// domain.
+///
+/// A collapsed DomainValue represents a single register that has been forced
+/// into one of more execution domains. There is a separate collapsed
+/// DomainValue for each register, but it may contain multiple execution
+/// domains. A register value is initially created in a single execution
+/// domain, but if we were forced to pay the penalty of a domain crossing, we
+/// keep track of the fact the the register is now available in multiple
+/// domains.
+namespace {
+struct DomainValue {
+  // Basic reference counting.
+  unsigned Refs;
+
+  // Bitmask of available domains. For an open DomainValue, it is the still
+  // possible domains for collapsing. For a collapsed DomainValue it is the
+  // domains where the register is available for free.
+  unsigned AvailableDomains;
+
+  // Position of the last defining instruction.
+  unsigned Dist;
+
+  // Twiddleable instructions using or defining these registers.
+  SmallVector<MachineInstr*, 8> Instrs;
+
+  // A collapsed DomainValue has no instructions to twiddle - it simply keeps
+  // track of the domains where the registers are already available.
+  bool isCollapsed() const { return Instrs.empty(); }
+
+  // Is domain available?
+  bool hasDomain(unsigned domain) const {
+    return AvailableDomains & (1u << domain);
+  }
+
+  // Mark domain as available.
+  void addDomain(unsigned domain) {
+    AvailableDomains |= 1u << domain;
+  }
+
+  // Restrict to a single domain available.
+  void setSingleDomain(unsigned domain) {
+    AvailableDomains = 1u << domain;
+  }
+
+  // Return bitmask of domains that are available and in mask.
+  unsigned getCommonDomains(unsigned mask) const {
+    return AvailableDomains & mask;
+  }
+
+  // First domain available.
+  unsigned getFirstDomain() const {
+    return CountTrailingZeros_32(AvailableDomains);
+  }
+
+  DomainValue() { clear(); }
+
+  void clear() {
+    Refs = AvailableDomains = Dist = 0;
+    Instrs.clear();
+  }
+};
+}
+
+namespace {
+class SSEDomainFixPass : public MachineFunctionPass {
+  static char ID;
+  SpecificBumpPtrAllocator<DomainValue> Allocator;
+  SmallVector<DomainValue*,16> Avail;
+
+  const TargetRegisterClass *const RC;
+  MachineFunction *MF;
+  const TargetInstrInfo *TII;
+  const TargetRegisterInfo *TRI;
+  MachineBasicBlock *MBB;
+  std::vector<int> AliasMap;
+  const unsigned NumRegs;
+  DomainValue **LiveRegs;
+  typedef DenseMap<MachineBasicBlock*,DomainValue**> LiveOutMap;
+  LiveOutMap LiveOuts;
+  unsigned Distance;
+
+public:
+  SSEDomainFixPass(const TargetRegisterClass *rc)
+    : MachineFunctionPass(ID), RC(rc), NumRegs(RC->getNumRegs()) {}
+
+  virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+    AU.setPreservesAll();
+    MachineFunctionPass::getAnalysisUsage(AU);
+  }
+
+  virtual bool runOnMachineFunction(MachineFunction &MF);
+
+  virtual const char *getPassName() const {
+    return "SSE execution domain fixup";
+  }
+
+private:
+  // Register mapping.
+  int RegIndex(unsigned Reg);
+
+  // DomainValue allocation.
+  DomainValue *Alloc(int domain = -1);
+  void Recycle(DomainValue*);
+
+  // LiveRegs manipulations.
+  void SetLiveReg(int rx, DomainValue *DV);
+  void Kill(int rx);
+  void Force(int rx, unsigned domain);
+  void Collapse(DomainValue *dv, unsigned domain);
+  bool Merge(DomainValue *A, DomainValue *B);
+
+  void enterBasicBlock();
+  void visitGenericInstr(MachineInstr*);
+  void visitSoftInstr(MachineInstr*, unsigned mask);
+  void visitHardInstr(MachineInstr*, unsigned domain);
+};
+}
+
+char SSEDomainFixPass::ID = 0;
+
+/// Translate TRI register number to an index into our smaller tables of
+/// interesting registers. Return -1 for boring registers.
+int SSEDomainFixPass::RegIndex(unsigned Reg) {
+  assert(Reg < AliasMap.size() && "Invalid register");
+  return AliasMap[Reg];
+}
+
+DomainValue *SSEDomainFixPass::Alloc(int domain) {
+  DomainValue *dv = Avail.empty() ?
+                      new(Allocator.Allocate()) DomainValue :
+                      Avail.pop_back_val();
+  dv->Dist = Distance;
+  if (domain >= 0)
+    dv->addDomain(domain);
+  return dv;
+}
+
+void SSEDomainFixPass::Recycle(DomainValue *dv) {
+  assert(dv && "Cannot recycle NULL");
+  dv->clear();
+  Avail.push_back(dv);
+}
+
+/// Set LiveRegs[rx] = dv, updating reference counts.
+void SSEDomainFixPass::SetLiveReg(int rx, DomainValue *dv) {
+  assert(unsigned(rx) < NumRegs && "Invalid index");
+  if (!LiveRegs) {
+    LiveRegs = new DomainValue*[NumRegs];
+    std::fill(LiveRegs, LiveRegs+NumRegs, (DomainValue*)0);
+  }
+
+  if (LiveRegs[rx] == dv)
+    return;
+  if (LiveRegs[rx]) {
+    assert(LiveRegs[rx]->Refs && "Bad refcount");
+    if (--LiveRegs[rx]->Refs == 0) Recycle(LiveRegs[rx]);
+  }
+  LiveRegs[rx] = dv;
+  if (dv) ++dv->Refs;
+}
+
+// Kill register rx, recycle or collapse any DomainValue.
+void SSEDomainFixPass::Kill(int rx) {
+  assert(unsigned(rx) < NumRegs && "Invalid index");
+  if (!LiveRegs || !LiveRegs[rx]) return;
+
+  // Before killing the last reference to an open DomainValue, collapse it to
+  // the first available domain.
+  if (LiveRegs[rx]->Refs == 1 && !LiveRegs[rx]->isCollapsed())
+    Collapse(LiveRegs[rx], LiveRegs[rx]->getFirstDomain());
+  else
+    SetLiveReg(rx, 0);
+}
+
+/// Force register rx into domain.
+void SSEDomainFixPass::Force(int rx, unsigned domain) {
+  assert(unsigned(rx) < NumRegs && "Invalid index");
+  DomainValue *dv;
+  if (LiveRegs && (dv = LiveRegs[rx])) {
+    if (dv->isCollapsed())
+      dv->addDomain(domain);
+    else if (dv->hasDomain(domain))
+      Collapse(dv, domain);
+    else {
+      // This is an incompatible open DomainValue. Collapse it to whatever and force
+      // the new value into domain. This costs a domain crossing.
+      Collapse(dv, dv->getFirstDomain());
+      assert(LiveRegs[rx] && "Not live after collapse?");
+      LiveRegs[rx]->addDomain(domain);
+    }
+  } else {
+    // Set up basic collapsed DomainValue.
+    SetLiveReg(rx, Alloc(domain));
+  }
+}
+
+/// Collapse open DomainValue into given domain. If there are multiple
+/// registers using dv, they each get a unique collapsed DomainValue.
+void SSEDomainFixPass::Collapse(DomainValue *dv, unsigned domain) {
+  assert(dv->hasDomain(domain) && "Cannot collapse");
+
+  // Collapse all the instructions.
+  while (!dv->Instrs.empty())
+    TII->setExecutionDomain(dv->Instrs.pop_back_val(), domain);
+  dv->setSingleDomain(domain);
+
+  // If there are multiple users, give them new, unique DomainValues.
+  if (LiveRegs && dv->Refs > 1)
+    for (unsigned rx = 0; rx != NumRegs; ++rx)
+      if (LiveRegs[rx] == dv)
+        SetLiveReg(rx, Alloc(domain));
+}
+
+/// Merge - All instructions and registers in B are moved to A, and B is
+/// released.
+bool SSEDomainFixPass::Merge(DomainValue *A, DomainValue *B) {
+  assert(!A->isCollapsed() && "Cannot merge into collapsed");
+  assert(!B->isCollapsed() && "Cannot merge from collapsed");
+  if (A == B)
+    return true;
+  // Restrict to the domains that A and B have in common.
+  unsigned common = A->getCommonDomains(B->AvailableDomains);
+  if (!common)
+    return false;
+  A->AvailableDomains = common;
+  A->Dist = std::max(A->Dist, B->Dist);
+  A->Instrs.append(B->Instrs.begin(), B->Instrs.end());
+  for (unsigned rx = 0; rx != NumRegs; ++rx)
+    if (LiveRegs[rx] == B)
+      SetLiveReg(rx, A);
+  return true;
+}
+
+void SSEDomainFixPass::enterBasicBlock() {
+  // Try to coalesce live-out registers from predecessors.
+  for (MachineBasicBlock::livein_iterator i = MBB->livein_begin(),
+         e = MBB->livein_end(); i != e; ++i) {
+    int rx = RegIndex(*i);
+    if (rx < 0) continue;
+    for (MachineBasicBlock::const_pred_iterator pi = MBB->pred_begin(),
+           pe = MBB->pred_end(); pi != pe; ++pi) {
+      LiveOutMap::const_iterator fi = LiveOuts.find(*pi);
+      if (fi == LiveOuts.end()) continue;
+      DomainValue *pdv = fi->second[rx];
+      if (!pdv) continue;
+      if (!LiveRegs || !LiveRegs[rx]) {
+        SetLiveReg(rx, pdv);
+        continue;
+      }
+
+      // We have a live DomainValue from more than one predecessor.
+      if (LiveRegs[rx]->isCollapsed()) {
+        // We are already collapsed, but predecessor is not. Force him.
+        unsigned domain = LiveRegs[rx]->getFirstDomain();
+        if (!pdv->isCollapsed() && pdv->hasDomain(domain))
+          Collapse(pdv, domain);
+        continue;
+      }
+
+      // Currently open, merge in predecessor.
+      if (!pdv->isCollapsed())
+        Merge(LiveRegs[rx], pdv);
+      else
+        Force(rx, pdv->getFirstDomain());
+    }
+  }
+}
+
+// A hard instruction only works in one domain. All input registers will be
+// forced into that domain.
+void SSEDomainFixPass::visitHardInstr(MachineInstr *mi, unsigned domain) {
+  // Collapse all uses.
+  for (unsigned i = mi->getDesc().getNumDefs(),
+                e = mi->getDesc().getNumOperands(); i != e; ++i) {
+    MachineOperand &mo = mi->getOperand(i);
+    if (!mo.isReg()) continue;
+    int rx = RegIndex(mo.getReg());
+    if (rx < 0) continue;
+    Force(rx, domain);
+  }
+
+  // Kill all defs and force them.
+  for (unsigned i = 0, e = mi->getDesc().getNumDefs(); i != e; ++i) {
+    MachineOperand &mo = mi->getOperand(i);
+    if (!mo.isReg()) continue;
+    int rx = RegIndex(mo.getReg());
+    if (rx < 0) continue;
+    Kill(rx);
+    Force(rx, domain);
+  }
+}
+
+// A soft instruction can be changed to work in other domains given by mask.
+void SSEDomainFixPass::visitSoftInstr(MachineInstr *mi, unsigned mask) {
+  // Bitmask of available domains for this instruction after taking collapsed
+  // operands into account.
+  unsigned available = mask;
+
+  // Scan the explicit use operands for incoming domains.
+  SmallVector<int, 4> used;
+  if (LiveRegs)
+    for (unsigned i = mi->getDesc().getNumDefs(),
+                  e = mi->getDesc().getNumOperands(); i != e; ++i) {
+      MachineOperand &mo = mi->getOperand(i);
+      if (!mo.isReg()) continue;
+      int rx = RegIndex(mo.getReg());
+      if (rx < 0) continue;
+      if (DomainValue *dv = LiveRegs[rx]) {
+        // Bitmask of domains that dv and available have in common.
+        unsigned common = dv->getCommonDomains(available);
+        // Is it possible to use this collapsed register for free?
+        if (dv->isCollapsed()) {
+          // Restrict available domains to the ones in common with the operand.
+          // If there are no common domains, we must pay the cross-domain 
+          // penalty for this operand.
+          if (common) available = common;
+        } else if (common)
+          // Open DomainValue is compatible, save it for merging.
+          used.push_back(rx);
+        else
+          // Open DomainValue is not compatible with instruction. It is useless
+          // now.
+          Kill(rx);
+      }
+    }
+
+  // If the collapsed operands force a single domain, propagate the collapse.
+  if (isPowerOf2_32(available)) {
+    unsigned domain = CountTrailingZeros_32(available);
+    TII->setExecutionDomain(mi, domain);
+    visitHardInstr(mi, domain);
+    return;
+  }
+
+  // Kill off any remaining uses that don't match available, and build a list of
+  // incoming DomainValues that we want to merge.
+  SmallVector<DomainValue*,4> doms;
+  for (SmallVector<int, 4>::iterator i=used.begin(), e=used.end(); i!=e; ++i) {
+    int rx = *i;
+    DomainValue *dv = LiveRegs[rx];
+    // This useless DomainValue could have been missed above.
+    if (!dv->getCommonDomains(available)) {
+      Kill(*i);
+      continue;
+    }
+    // sorted, uniqued insert.
+    bool inserted = false;
+    for (SmallVector<DomainValue*,4>::iterator i = doms.begin(), e = doms.end();
+           i != e && !inserted; ++i) {
+      if (dv == *i)
+        inserted = true;
+      else if (dv->Dist < (*i)->Dist) {
+        inserted = true;
+        doms.insert(i, dv);
+      }
+    }
+    if (!inserted)
+      doms.push_back(dv);
+  }
+
+  // doms are now sorted in order of appearance. Try to merge them all, giving
+  // priority to the latest ones.
+  DomainValue *dv = 0;
+  while (!doms.empty()) {
+    if (!dv) {
+      dv = doms.pop_back_val();
+      continue;
+    }
+
+    DomainValue *latest = doms.pop_back_val();
+    if (Merge(dv, latest)) continue;
+
+    // If latest didn't merge, it is useless now. Kill all registers using it.
+    for (SmallVector<int,4>::iterator i=used.begin(), e=used.end(); i != e; ++i)
+      if (LiveRegs[*i] == latest)
+        Kill(*i);
+  }
+
+  // dv is the DomainValue we are going to use for this instruction.
+  if (!dv)
+    dv = Alloc();
+  dv->Dist = Distance;
+  dv->AvailableDomains = available;
+  dv->Instrs.push_back(mi);
+
+  // Finally set all defs and non-collapsed uses to dv.
+  for (unsigned i = 0, e = mi->getDesc().getNumOperands(); i != e; ++i) {
+    MachineOperand &mo = mi->getOperand(i);
+    if (!mo.isReg()) continue;
+    int rx = RegIndex(mo.getReg());
+    if (rx < 0) continue;
+    if (!LiveRegs || !LiveRegs[rx] || (mo.isDef() && LiveRegs[rx]!=dv)) {
+      Kill(rx);
+      SetLiveReg(rx, dv);
+    }
+  }
+}
+
+void SSEDomainFixPass::visitGenericInstr(MachineInstr *mi) {
+  // Process explicit defs, kill any XMM registers redefined.
+  for (unsigned i = 0, e = mi->getDesc().getNumDefs(); i != e; ++i) {
+    MachineOperand &mo = mi->getOperand(i);
+    if (!mo.isReg()) continue;
+    int rx = RegIndex(mo.getReg());
+    if (rx < 0) continue;
+    Kill(rx);
+  }
+}
+
+bool SSEDomainFixPass::runOnMachineFunction(MachineFunction &mf) {
+  MF = &mf;
+  TII = MF->getTarget().getInstrInfo();
+  TRI = MF->getTarget().getRegisterInfo();
+  MBB = 0;
+  LiveRegs = 0;
+  Distance = 0;
+  assert(NumRegs == RC->getNumRegs() && "Bad regclass");
+
+  // If no XMM registers are used in the function, we can skip it completely.
+  bool anyregs = false;
+  for (TargetRegisterClass::const_iterator I = RC->begin(), E = RC->end();
+       I != E; ++I)
+    if (MF->getRegInfo().isPhysRegUsed(*I)) {
+      anyregs = true;
+      break;
+    }
+  if (!anyregs) return false;
+
+  // Initialize the AliasMap on the first use.
+  if (AliasMap.empty()) {
+    // Given a PhysReg, AliasMap[PhysReg] is either the relevant index into RC,
+    // or -1.
+    AliasMap.resize(TRI->getNumRegs(), -1);
+    for (unsigned i = 0, e = RC->getNumRegs(); i != e; ++i)
+      for (const unsigned *AI = TRI->getOverlaps(RC->getRegister(i)); *AI; ++AI)
+        AliasMap[*AI] = i;
+  }
+
+  MachineBasicBlock *Entry = MF->begin();
+  SmallPtrSet<MachineBasicBlock*, 16> Visited;
+  for (df_ext_iterator<MachineBasicBlock*, SmallPtrSet<MachineBasicBlock*, 16> >
+         DFI = df_ext_begin(Entry, Visited), DFE = df_ext_end(Entry, Visited);
+         DFI != DFE; ++DFI) {
+    MBB = *DFI;
+    enterBasicBlock();
+    for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
+        ++I) {
+      MachineInstr *mi = I;
+      if (mi->isDebugValue()) continue;
+      ++Distance;
+      std::pair<uint16_t, uint16_t> domp = TII->getExecutionDomain(mi);
+      if (domp.first)
+        if (domp.second)
+          visitSoftInstr(mi, domp.second);
+        else
+          visitHardInstr(mi, domp.first);
+      else if (LiveRegs)
+        visitGenericInstr(mi);
+    }
+
+    // Save live registers at end of MBB - used by enterBasicBlock().
+    if (LiveRegs)
+      LiveOuts.insert(std::make_pair(MBB, LiveRegs));
+    LiveRegs = 0;
+  }
+
+  // Clear the LiveOuts vectors. Should we also collapse any remaining
+  // DomainValues?
+  for (LiveOutMap::const_iterator i = LiveOuts.begin(), e = LiveOuts.end();
+         i != e; ++i)
+    delete[] i->second;
+  LiveOuts.clear();
+  Avail.clear();
+  Allocator.DestroyAll();
+
+  return false;
+}
+
+FunctionPass *
+llvm::createExecutionDependencyFixPass(const TargetRegisterClass *RC) {
+  return new SSEDomainFixPass(RC);
+}