1 files changed, 448 insertions, 0 deletions
diff --git a/contrib/llvm-project/llvm/lib/Target/AMDGPU/SIOptimizeExecMaskingPreRA.cpp b/contrib/llvm-project/llvm/lib/Target/AMDGPU/SIOptimizeExecMaskingPreRA.cpp
new file mode 100644
index 000000000000..7e10316eab92
--- /dev/null
+++ b/contrib/llvm-project/llvm/lib/Target/AMDGPU/SIOptimizeExecMaskingPreRA.cpp
@@ -0,0 +1,448 @@
+//===-- SIOptimizeExecMaskingPreRA.cpp ------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file
+/// This pass removes redundant S_OR_B64 instructions enabling lanes in
+/// the exec. If two SI_END_CF (lowered as S_OR_B64) come together without any
+/// vector instructions between them we can only keep outer SI_END_CF, given
+/// that CFG is structured and exec bits of the outer end statement are always
+/// not less than exec bit of the inner one.
+///
+/// This needs to be done before the RA to eliminate saved exec bits registers
+/// but after register coalescer to have no vector registers copies in between
+/// of different end cf statements.
+///
+//===----------------------------------------------------------------------===//
+
+#include "AMDGPU.h"
+#include "AMDGPUSubtarget.h"
+#include "SIInstrInfo.h"
+#include "MCTargetDesc/AMDGPUMCTargetDesc.h"
+#include "llvm/CodeGen/LiveIntervals.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "si-optimize-exec-masking-pre-ra"
+
+namespace {
+
+class SIOptimizeExecMaskingPreRA : public MachineFunctionPass {
+private:
+  const SIRegisterInfo *TRI;
+  const SIInstrInfo *TII;
+  MachineRegisterInfo *MRI;
+
+public:
+  MachineBasicBlock::iterator skipIgnoreExecInsts(
+    MachineBasicBlock::iterator I, MachineBasicBlock::iterator E) const;
+
+    MachineBasicBlock::iterator skipIgnoreExecInstsTrivialSucc(
+      MachineBasicBlock *&MBB,
+      MachineBasicBlock::iterator It) const;
+
+public:
+  static char ID;
+
+  SIOptimizeExecMaskingPreRA() : MachineFunctionPass(ID) {
+    initializeSIOptimizeExecMaskingPreRAPass(*PassRegistry::getPassRegistry());
+  }
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+  StringRef getPassName() const override {
+    return "SI optimize exec mask operations pre-RA";
+  }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.addRequired<LiveIntervals>();
+    AU.setPreservesAll();
+    MachineFunctionPass::getAnalysisUsage(AU);
+  }
+};
+
+} // End anonymous namespace.
+
+INITIALIZE_PASS_BEGIN(SIOptimizeExecMaskingPreRA, DEBUG_TYPE,
+                      "SI optimize exec mask operations pre-RA", false, false)
+INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
+INITIALIZE_PASS_END(SIOptimizeExecMaskingPreRA, DEBUG_TYPE,
+                    "SI optimize exec mask operations pre-RA", false, false)
+
+char SIOptimizeExecMaskingPreRA::ID = 0;
+
+char &llvm::SIOptimizeExecMaskingPreRAID = SIOptimizeExecMaskingPreRA::ID;
+
+FunctionPass *llvm::createSIOptimizeExecMaskingPreRAPass() {
+  return new SIOptimizeExecMaskingPreRA();
+}
+
+static bool isEndCF(const MachineInstr &MI, const SIRegisterInfo *TRI,
+                    const GCNSubtarget &ST) {
+  if (ST.isWave32()) {
+    return MI.getOpcode() == AMDGPU::S_OR_B32 &&
+           MI.modifiesRegister(AMDGPU::EXEC_LO, TRI);
+  }
+
+  return MI.getOpcode() == AMDGPU::S_OR_B64 &&
+         MI.modifiesRegister(AMDGPU::EXEC, TRI);
+}
+
+static bool isFullExecCopy(const MachineInstr& MI, const GCNSubtarget& ST) {
+  unsigned Exec = ST.isWave32() ? AMDGPU::EXEC_LO : AMDGPU::EXEC;
+
+  if (MI.isCopy() && MI.getOperand(1).getReg() == Exec) {
+    assert(MI.isFullCopy());
+    return true;
+  }
+
+  return false;
+}
+
+static unsigned getOrNonExecReg(const MachineInstr &MI,
+                                const SIInstrInfo &TII,
+                                const GCNSubtarget& ST) {
+  unsigned Exec = ST.isWave32() ? AMDGPU::EXEC_LO : AMDGPU::EXEC;
+  auto Op = TII.getNamedOperand(MI, AMDGPU::OpName::src1);
+  if (Op->isReg() && Op->getReg() != Exec)
+     return Op->getReg();
+  Op = TII.getNamedOperand(MI, AMDGPU::OpName::src0);
+  if (Op->isReg() && Op->getReg() != Exec)
+     return Op->getReg();
+  return AMDGPU::NoRegister;
+}
+
+static MachineInstr* getOrExecSource(const MachineInstr &MI,
+                                     const SIInstrInfo &TII,
+                                     const MachineRegisterInfo &MRI,
+                                     const GCNSubtarget& ST) {
+  auto SavedExec = getOrNonExecReg(MI, TII, ST);
+  if (SavedExec == AMDGPU::NoRegister)
+    return nullptr;
+  auto SaveExecInst = MRI.getUniqueVRegDef(SavedExec);
+  if (!SaveExecInst || !isFullExecCopy(*SaveExecInst, ST))
+    return nullptr;
+  return SaveExecInst;
+}
+
+/// Skip over instructions that don't care about the exec mask.
+MachineBasicBlock::iterator SIOptimizeExecMaskingPreRA::skipIgnoreExecInsts(
+  MachineBasicBlock::iterator I, MachineBasicBlock::iterator E) const {
+  for ( ; I != E; ++I) {
+    if (TII->mayReadEXEC(*MRI, *I))
+      break;
+  }
+
+  return I;
+}
+
+// Skip to the next instruction, ignoring debug instructions, and trivial block
+// boundaries (blocks that have one (typically fallthrough) successor, and the
+// successor has one predecessor.
+MachineBasicBlock::iterator
+SIOptimizeExecMaskingPreRA::skipIgnoreExecInstsTrivialSucc(
+  MachineBasicBlock *&MBB,
+  MachineBasicBlock::iterator It) const {
+
+  do {
+    It = skipIgnoreExecInsts(It, MBB->end());
+    if (It != MBB->end() || MBB->succ_size() != 1)
+      break;
+
+    // If there is one trivial successor, advance to the next block.
+    MachineBasicBlock *Succ = *MBB->succ_begin();
+
+    // TODO: Is this really necessary?
+    if (!MBB->isLayoutSuccessor(Succ))
+      break;
+
+    It = Succ->begin();
+    MBB = Succ;
+  } while (true);
+
+  return It;
+}
+
+
+// Optimize sequence
+//    %sel = V_CNDMASK_B32_e64 0, 1, %cc
+//    %cmp = V_CMP_NE_U32 1, %1
+//    $vcc = S_AND_B64 $exec, %cmp
+//    S_CBRANCH_VCC[N]Z
+// =>
+//    $vcc = S_ANDN2_B64 $exec, %cc
+//    S_CBRANCH_VCC[N]Z
+//
+// It is the negation pattern inserted by DAGCombiner::visitBRCOND() in the
+// rebuildSetCC(). We start with S_CBRANCH to avoid exhaustive search, but
+// only 3 first instructions are really needed. S_AND_B64 with exec is a
+// required part of the pattern since V_CNDMASK_B32 writes zeroes for inactive
+// lanes.
+//
+// Returns %cc register on success.
+static unsigned optimizeVcndVcmpPair(MachineBasicBlock &MBB,
+                                     const GCNSubtarget &ST,
+                                     MachineRegisterInfo &MRI,
+                                     LiveIntervals *LIS) {
+  const SIRegisterInfo *TRI = ST.getRegisterInfo();
+  const SIInstrInfo *TII = ST.getInstrInfo();
+  bool Wave32 = ST.isWave32();
+  const unsigned AndOpc = Wave32 ? AMDGPU::S_AND_B32 : AMDGPU::S_AND_B64;
+  const unsigned Andn2Opc = Wave32 ? AMDGPU::S_ANDN2_B32 : AMDGPU::S_ANDN2_B64;
+  const unsigned CondReg = Wave32 ? AMDGPU::VCC_LO : AMDGPU::VCC;
+  const unsigned ExecReg = Wave32 ? AMDGPU::EXEC_LO : AMDGPU::EXEC;
+
+  auto I = llvm::find_if(MBB.terminators(), [](const MachineInstr &MI) {
+                           unsigned Opc = MI.getOpcode();
+                           return Opc == AMDGPU::S_CBRANCH_VCCZ ||
+                                  Opc == AMDGPU::S_CBRANCH_VCCNZ; });
+  if (I == MBB.terminators().end())
+    return AMDGPU::NoRegister;
+
+  auto *And = TRI->findReachingDef(CondReg, AMDGPU::NoSubRegister,
+                                   *I, MRI, LIS);
+  if (!And || And->getOpcode() != AndOpc ||
+      !And->getOperand(1).isReg() || !And->getOperand(2).isReg())
+    return AMDGPU::NoRegister;
+
+  MachineOperand *AndCC = &And->getOperand(1);
+  unsigned CmpReg = AndCC->getReg();
+  unsigned CmpSubReg = AndCC->getSubReg();
+  if (CmpReg == ExecReg) {
+    AndCC = &And->getOperand(2);
+    CmpReg = AndCC->getReg();
+    CmpSubReg = AndCC->getSubReg();
+  } else if (And->getOperand(2).getReg() != ExecReg) {
+    return AMDGPU::NoRegister;
+  }
+
+  auto *Cmp = TRI->findReachingDef(CmpReg, CmpSubReg, *And, MRI, LIS);
+  if (!Cmp || !(Cmp->getOpcode() == AMDGPU::V_CMP_NE_U32_e32 ||
+                Cmp->getOpcode() == AMDGPU::V_CMP_NE_U32_e64) ||
+      Cmp->getParent() != And->getParent())
+    return AMDGPU::NoRegister;
+
+  MachineOperand *Op1 = TII->getNamedOperand(*Cmp, AMDGPU::OpName::src0);
+  MachineOperand *Op2 = TII->getNamedOperand(*Cmp, AMDGPU::OpName::src1);
+  if (Op1->isImm() && Op2->isReg())
+    std::swap(Op1, Op2);
+  if (!Op1->isReg() || !Op2->isImm() || Op2->getImm() != 1)
+    return AMDGPU::NoRegister;
+
+  unsigned SelReg = Op1->getReg();
+  auto *Sel = TRI->findReachingDef(SelReg, Op1->getSubReg(), *Cmp, MRI, LIS);
+  if (!Sel || Sel->getOpcode() != AMDGPU::V_CNDMASK_B32_e64)
+    return AMDGPU::NoRegister;
+
+  if (TII->hasModifiersSet(*Sel, AMDGPU::OpName::src0_modifiers) ||
+      TII->hasModifiersSet(*Sel, AMDGPU::OpName::src1_modifiers))
+    return AMDGPU::NoRegister;
+
+  Op1 = TII->getNamedOperand(*Sel, AMDGPU::OpName::src0);
+  Op2 = TII->getNamedOperand(*Sel, AMDGPU::OpName::src1);
+  MachineOperand *CC = TII->getNamedOperand(*Sel, AMDGPU::OpName::src2);
+  if (!Op1->isImm() || !Op2->isImm() || !CC->isReg() ||
+      Op1->getImm() != 0 || Op2->getImm() != 1)
+    return AMDGPU::NoRegister;
+
+  LLVM_DEBUG(dbgs() << "Folding sequence:\n\t" << *Sel << '\t'
+                    << *Cmp << '\t' << *And);
+
+  unsigned CCReg = CC->getReg();
+  LIS->RemoveMachineInstrFromMaps(*And);
+  MachineInstr *Andn2 = BuildMI(MBB, *And, And->getDebugLoc(),
+                                TII->get(Andn2Opc), And->getOperand(0).getReg())
+                            .addReg(ExecReg)
+                            .addReg(CCReg, 0, CC->getSubReg());
+  And->eraseFromParent();
+  LIS->InsertMachineInstrInMaps(*Andn2);
+
+  LLVM_DEBUG(dbgs() << "=>\n\t" << *Andn2 << '\n');
+
+  // Try to remove compare. Cmp value should not used in between of cmp
+  // and s_and_b64 if VCC or just unused if any other register.
+  if ((TargetRegisterInfo::isVirtualRegister(CmpReg) &&
+       MRI.use_nodbg_empty(CmpReg)) ||
+      (CmpReg == CondReg &&
+       std::none_of(std::next(Cmp->getIterator()), Andn2->getIterator(),
+                    [&](const MachineInstr &MI) {
+                      return MI.readsRegister(CondReg, TRI); }))) {
+    LLVM_DEBUG(dbgs() << "Erasing: " << *Cmp << '\n');
+
+    LIS->RemoveMachineInstrFromMaps(*Cmp);
+    Cmp->eraseFromParent();
+
+    // Try to remove v_cndmask_b32.
+    if (TargetRegisterInfo::isVirtualRegister(SelReg) &&
+        MRI.use_nodbg_empty(SelReg)) {
+      LLVM_DEBUG(dbgs() << "Erasing: " << *Sel << '\n');
+
+      LIS->RemoveMachineInstrFromMaps(*Sel);
+      Sel->eraseFromParent();
+    }
+  }
+
+  return CCReg;
+}
+
+bool SIOptimizeExecMaskingPreRA::runOnMachineFunction(MachineFunction &MF) {
+  if (skipFunction(MF.getFunction()))
+    return false;
+
+  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
+  TRI = ST.getRegisterInfo();
+  TII = ST.getInstrInfo();
+  MRI = &MF.getRegInfo();
+
+  MachineRegisterInfo &MRI = MF.getRegInfo();
+  LiveIntervals *LIS = &getAnalysis<LiveIntervals>();
+  DenseSet<unsigned> RecalcRegs({AMDGPU::EXEC_LO, AMDGPU::EXEC_HI});
+  unsigned Exec = ST.isWave32() ? AMDGPU::EXEC_LO : AMDGPU::EXEC;
+  bool Changed = false;
+
+  for (MachineBasicBlock &MBB : MF) {
+
+    if (unsigned Reg = optimizeVcndVcmpPair(MBB, ST, MRI, LIS)) {
+      RecalcRegs.insert(Reg);
+      RecalcRegs.insert(AMDGPU::VCC_LO);
+      RecalcRegs.insert(AMDGPU::VCC_HI);
+      RecalcRegs.insert(AMDGPU::SCC);
+      Changed = true;
+    }
+
+    // Try to remove unneeded instructions before s_endpgm.
+    if (MBB.succ_empty()) {
+      if (MBB.empty())
+        continue;
+
+      // Skip this if the endpgm has any implicit uses, otherwise we would need
+      // to be careful to update / remove them.
+      // S_ENDPGM always has a single imm operand that is not used other than to
+      // end up in the encoding
+      MachineInstr &Term = MBB.back();
+      if (Term.getOpcode() != AMDGPU::S_ENDPGM || Term.getNumOperands() != 1)
+        continue;
+
+      SmallVector<MachineBasicBlock*, 4> Blocks({&MBB});
+
+      while (!Blocks.empty()) {
+        auto CurBB = Blocks.pop_back_val();
+        auto I = CurBB->rbegin(), E = CurBB->rend();
+        if (I != E) {
+          if (I->isUnconditionalBranch() || I->getOpcode() == AMDGPU::S_ENDPGM)
+            ++I;
+          else if (I->isBranch())
+            continue;
+        }
+
+        while (I != E) {
+          if (I->isDebugInstr()) {
+            I = std::next(I);
+            continue;
+          }
+
+          if (I->mayStore() || I->isBarrier() || I->isCall() ||
+              I->hasUnmodeledSideEffects() || I->hasOrderedMemoryRef())
+            break;
+
+          LLVM_DEBUG(dbgs()
+                     << "Removing no effect instruction: " << *I << '\n');
+
+          for (auto &Op : I->operands()) {
+            if (Op.isReg())
+              RecalcRegs.insert(Op.getReg());
+          }
+
+          auto Next = std::next(I);
+          LIS->RemoveMachineInstrFromMaps(*I);
+          I->eraseFromParent();
+          I = Next;
+
+          Changed = true;
+        }
+
+        if (I != E)
+          continue;
+
+        // Try to ascend predecessors.
+        for (auto *Pred : CurBB->predecessors()) {
+          if (Pred->succ_size() == 1)
+            Blocks.push_back(Pred);
+        }
+      }
+      continue;
+    }
+
+    // Try to collapse adjacent endifs.
+    auto E = MBB.end();
+    auto Lead = skipDebugInstructionsForward(MBB.begin(), E);
+    if (MBB.succ_size() != 1 || Lead == E || !isEndCF(*Lead, TRI, ST))
+      continue;
+
+    MachineBasicBlock *TmpMBB = &MBB;
+    auto NextLead = skipIgnoreExecInstsTrivialSucc(TmpMBB, std::next(Lead));
+    if (NextLead == TmpMBB->end() || !isEndCF(*NextLead, TRI, ST) ||
+        !getOrExecSource(*NextLead, *TII, MRI, ST))
+      continue;
+
+    LLVM_DEBUG(dbgs() << "Redundant EXEC = S_OR_B64 found: " << *Lead << '\n');
+
+    auto SaveExec = getOrExecSource(*Lead, *TII, MRI, ST);
+    unsigned SaveExecReg = getOrNonExecReg(*Lead, *TII, ST);
+    for (auto &Op : Lead->operands()) {
+      if (Op.isReg())
+        RecalcRegs.insert(Op.getReg());
+    }
+
+    LIS->RemoveMachineInstrFromMaps(*Lead);
+    Lead->eraseFromParent();
+    if (SaveExecReg) {
+      LIS->removeInterval(SaveExecReg);
+      LIS->createAndComputeVirtRegInterval(SaveExecReg);
+    }
+
+    Changed = true;
+
+    // If the only use of saved exec in the removed instruction is S_AND_B64
+    // fold the copy now.
+    if (!SaveExec || !SaveExec->isFullCopy())
+      continue;
+
+    unsigned SavedExec = SaveExec->getOperand(0).getReg();
+    bool SafeToReplace = true;
+    for (auto& U : MRI.use_nodbg_instructions(SavedExec)) {
+      if (U.getParent() != SaveExec->getParent()) {
+        SafeToReplace = false;
+        break;
+      }
+
+      LLVM_DEBUG(dbgs() << "Redundant EXEC COPY: " << *SaveExec << '\n');
+    }
+
+    if (SafeToReplace) {
+      LIS->RemoveMachineInstrFromMaps(*SaveExec);
+      SaveExec->eraseFromParent();
+      MRI.replaceRegWith(SavedExec, Exec);
+      LIS->removeInterval(SavedExec);
+    }
+  }
+
+  if (Changed) {
+    for (auto Reg : RecalcRegs) {
+      if (TargetRegisterInfo::isVirtualRegister(Reg)) {
+        LIS->removeInterval(Reg);
+        if (!MRI.reg_empty(Reg))
+          LIS->createAndComputeVirtRegInterval(Reg);
+      } else {
+        LIS->removeAllRegUnitsForPhysReg(Reg);
+      }
+    }
+  }
+
+  return Changed;
+}