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-rw-r--r--contrib/llvm/lib/Target/AMDGPU/SILowerControlFlow.cpp473
1 files changed, 473 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Target/AMDGPU/SILowerControlFlow.cpp b/contrib/llvm/lib/Target/AMDGPU/SILowerControlFlow.cpp
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index 000000000000..5f1c7f1fc42f
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+++ b/contrib/llvm/lib/Target/AMDGPU/SILowerControlFlow.cpp
@@ -0,0 +1,473 @@
+//===-- SILowerControlFlow.cpp - Use predicates for control flow ----------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file
+/// \brief This pass lowers the pseudo control flow instructions to real
+/// machine instructions.
+///
+/// All control flow is handled using predicated instructions and
+/// a predicate stack. Each Scalar ALU controls the operations of 64 Vector
+/// ALUs. The Scalar ALU can update the predicate for any of the Vector ALUs
+/// by writting to the 64-bit EXEC register (each bit corresponds to a
+/// single vector ALU). Typically, for predicates, a vector ALU will write
+/// to its bit of the VCC register (like EXEC VCC is 64-bits, one for each
+/// Vector ALU) and then the ScalarALU will AND the VCC register with the
+/// EXEC to update the predicates.
+///
+/// For example:
+/// %VCC = V_CMP_GT_F32 %VGPR1, %VGPR2
+/// %SGPR0 = SI_IF %VCC
+/// %VGPR0 = V_ADD_F32 %VGPR0, %VGPR0
+/// %SGPR0 = SI_ELSE %SGPR0
+/// %VGPR0 = V_SUB_F32 %VGPR0, %VGPR0
+/// SI_END_CF %SGPR0
+///
+/// becomes:
+///
+/// %SGPR0 = S_AND_SAVEEXEC_B64 %VCC // Save and update the exec mask
+/// %SGPR0 = S_XOR_B64 %SGPR0, %EXEC // Clear live bits from saved exec mask
+/// S_CBRANCH_EXECZ label0 // This instruction is an optional
+/// // optimization which allows us to
+/// // branch if all the bits of
+/// // EXEC are zero.
+/// %VGPR0 = V_ADD_F32 %VGPR0, %VGPR0 // Do the IF block of the branch
+///
+/// label0:
+/// %SGPR0 = S_OR_SAVEEXEC_B64 %EXEC // Restore the exec mask for the Then block
+/// %EXEC = S_XOR_B64 %SGPR0, %EXEC // Clear live bits from saved exec mask
+/// S_BRANCH_EXECZ label1 // Use our branch optimization
+/// // instruction again.
+/// %VGPR0 = V_SUB_F32 %VGPR0, %VGPR // Do the THEN block
+/// label1:
+/// %EXEC = S_OR_B64 %EXEC, %SGPR0 // Re-enable saved exec mask bits
+//===----------------------------------------------------------------------===//
+
+#include "AMDGPU.h"
+#include "AMDGPUSubtarget.h"
+#include "SIInstrInfo.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/CodeGen/LiveIntervalAnalysis.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineOperand.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/SlotIndexes.h"
+#include "llvm/MC/MCRegisterInfo.h"
+#include "llvm/Pass.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+#include <cassert>
+#include <iterator>
+
+using namespace llvm;
+
+#define DEBUG_TYPE "si-lower-control-flow"
+
+namespace {
+
+class SILowerControlFlow : public MachineFunctionPass {
+private:
+ const SIRegisterInfo *TRI = nullptr;
+ const SIInstrInfo *TII = nullptr;
+ LiveIntervals *LIS = nullptr;
+ MachineRegisterInfo *MRI = nullptr;
+
+ void emitIf(MachineInstr &MI);
+ void emitElse(MachineInstr &MI);
+ void emitBreak(MachineInstr &MI);
+ void emitIfBreak(MachineInstr &MI);
+ void emitElseBreak(MachineInstr &MI);
+ void emitLoop(MachineInstr &MI);
+ void emitEndCf(MachineInstr &MI);
+
+ void findMaskOperands(MachineInstr &MI, unsigned OpNo,
+ SmallVectorImpl<MachineOperand> &Src) const;
+
+ void combineMasks(MachineInstr &MI);
+
+public:
+ static char ID;
+
+ SILowerControlFlow() : MachineFunctionPass(ID) {}
+
+ bool runOnMachineFunction(MachineFunction &MF) override;
+
+ StringRef getPassName() const override {
+ return "SI Lower control flow pseudo instructions";
+ }
+
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
+ // Should preserve the same set that TwoAddressInstructions does.
+ AU.addPreserved<SlotIndexes>();
+ AU.addPreserved<LiveIntervals>();
+ AU.addPreservedID(LiveVariablesID);
+ AU.addPreservedID(MachineLoopInfoID);
+ AU.addPreservedID(MachineDominatorsID);
+ AU.setPreservesCFG();
+ MachineFunctionPass::getAnalysisUsage(AU);
+ }
+};
+
+} // end anonymous namespace
+
+char SILowerControlFlow::ID = 0;
+
+INITIALIZE_PASS(SILowerControlFlow, DEBUG_TYPE,
+ "SI lower control flow", false, false)
+
+static void setImpSCCDefDead(MachineInstr &MI, bool IsDead) {
+ MachineOperand &ImpDefSCC = MI.getOperand(3);
+ assert(ImpDefSCC.getReg() == AMDGPU::SCC && ImpDefSCC.isDef());
+
+ ImpDefSCC.setIsDead(IsDead);
+}
+
+char &llvm::SILowerControlFlowID = SILowerControlFlow::ID;
+
+void SILowerControlFlow::emitIf(MachineInstr &MI) {
+ MachineBasicBlock &MBB = *MI.getParent();
+ const DebugLoc &DL = MI.getDebugLoc();
+ MachineBasicBlock::iterator I(&MI);
+
+ MachineOperand &SaveExec = MI.getOperand(0);
+ MachineOperand &Cond = MI.getOperand(1);
+ assert(SaveExec.getSubReg() == AMDGPU::NoSubRegister &&
+ Cond.getSubReg() == AMDGPU::NoSubRegister);
+
+ unsigned SaveExecReg = SaveExec.getReg();
+
+ MachineOperand &ImpDefSCC = MI.getOperand(4);
+ assert(ImpDefSCC.getReg() == AMDGPU::SCC && ImpDefSCC.isDef());
+
+ // Add an implicit def of exec to discourage scheduling VALU after this which
+ // will interfere with trying to form s_and_saveexec_b64 later.
+ unsigned CopyReg = MRI->createVirtualRegister(&AMDGPU::SReg_64RegClass);
+ MachineInstr *CopyExec =
+ BuildMI(MBB, I, DL, TII->get(AMDGPU::COPY), CopyReg)
+ .addReg(AMDGPU::EXEC)
+ .addReg(AMDGPU::EXEC, RegState::ImplicitDefine);
+
+ unsigned Tmp = MRI->createVirtualRegister(&AMDGPU::SReg_64RegClass);
+
+ MachineInstr *And =
+ BuildMI(MBB, I, DL, TII->get(AMDGPU::S_AND_B64), Tmp)
+ .addReg(CopyReg)
+ //.addReg(AMDGPU::EXEC)
+ .addReg(Cond.getReg());
+ setImpSCCDefDead(*And, true);
+
+ MachineInstr *Xor =
+ BuildMI(MBB, I, DL, TII->get(AMDGPU::S_XOR_B64), SaveExecReg)
+ .addReg(Tmp)
+ .addReg(CopyReg);
+ setImpSCCDefDead(*Xor, ImpDefSCC.isDead());
+
+ // Use a copy that is a terminator to get correct spill code placement it with
+ // fast regalloc.
+ MachineInstr *SetExec =
+ BuildMI(MBB, I, DL, TII->get(AMDGPU::S_MOV_B64_term), AMDGPU::EXEC)
+ .addReg(Tmp, RegState::Kill);
+
+ // Insert a pseudo terminator to help keep the verifier happy. This will also
+ // be used later when inserting skips.
+ MachineInstr *NewBr = BuildMI(MBB, I, DL, TII->get(AMDGPU::SI_MASK_BRANCH))
+ .add(MI.getOperand(2));
+
+ if (!LIS) {
+ MI.eraseFromParent();
+ return;
+ }
+
+ LIS->InsertMachineInstrInMaps(*CopyExec);
+
+ // Replace with and so we don't need to fix the live interval for condition
+ // register.
+ LIS->ReplaceMachineInstrInMaps(MI, *And);
+
+ LIS->InsertMachineInstrInMaps(*Xor);
+ LIS->InsertMachineInstrInMaps(*SetExec);
+ LIS->InsertMachineInstrInMaps(*NewBr);
+
+ LIS->removeRegUnit(*MCRegUnitIterator(AMDGPU::EXEC, TRI));
+ MI.eraseFromParent();
+
+ // FIXME: Is there a better way of adjusting the liveness? It shouldn't be
+ // hard to add another def here but I'm not sure how to correctly update the
+ // valno.
+ LIS->removeInterval(SaveExecReg);
+ LIS->createAndComputeVirtRegInterval(SaveExecReg);
+ LIS->createAndComputeVirtRegInterval(Tmp);
+ LIS->createAndComputeVirtRegInterval(CopyReg);
+}
+
+void SILowerControlFlow::emitElse(MachineInstr &MI) {
+ MachineBasicBlock &MBB = *MI.getParent();
+ const DebugLoc &DL = MI.getDebugLoc();
+
+ unsigned DstReg = MI.getOperand(0).getReg();
+ assert(MI.getOperand(0).getSubReg() == AMDGPU::NoSubRegister);
+
+ bool ExecModified = MI.getOperand(3).getImm() != 0;
+ MachineBasicBlock::iterator Start = MBB.begin();
+
+ // We are running before TwoAddressInstructions, and si_else's operands are
+ // tied. In order to correctly tie the registers, split this into a copy of
+ // the src like it does.
+ unsigned CopyReg = MRI->createVirtualRegister(&AMDGPU::SReg_64RegClass);
+ MachineInstr *CopyExec =
+ BuildMI(MBB, Start, DL, TII->get(AMDGPU::COPY), CopyReg)
+ .add(MI.getOperand(1)); // Saved EXEC
+
+ // This must be inserted before phis and any spill code inserted before the
+ // else.
+ unsigned SaveReg = ExecModified ?
+ MRI->createVirtualRegister(&AMDGPU::SReg_64RegClass) : DstReg;
+ MachineInstr *OrSaveExec =
+ BuildMI(MBB, Start, DL, TII->get(AMDGPU::S_OR_SAVEEXEC_B64), SaveReg)
+ .addReg(CopyReg);
+
+ MachineBasicBlock *DestBB = MI.getOperand(2).getMBB();
+
+ MachineBasicBlock::iterator ElsePt(MI);
+
+ if (ExecModified) {
+ MachineInstr *And =
+ BuildMI(MBB, ElsePt, DL, TII->get(AMDGPU::S_AND_B64), DstReg)
+ .addReg(AMDGPU::EXEC)
+ .addReg(SaveReg);
+
+ if (LIS)
+ LIS->InsertMachineInstrInMaps(*And);
+ }
+
+ MachineInstr *Xor =
+ BuildMI(MBB, ElsePt, DL, TII->get(AMDGPU::S_XOR_B64_term), AMDGPU::EXEC)
+ .addReg(AMDGPU::EXEC)
+ .addReg(DstReg);
+
+ MachineInstr *Branch =
+ BuildMI(MBB, ElsePt, DL, TII->get(AMDGPU::SI_MASK_BRANCH))
+ .addMBB(DestBB);
+
+ if (!LIS) {
+ MI.eraseFromParent();
+ return;
+ }
+
+ LIS->RemoveMachineInstrFromMaps(MI);
+ MI.eraseFromParent();
+
+ LIS->InsertMachineInstrInMaps(*CopyExec);
+ LIS->InsertMachineInstrInMaps(*OrSaveExec);
+
+ LIS->InsertMachineInstrInMaps(*Xor);
+ LIS->InsertMachineInstrInMaps(*Branch);
+
+ // src reg is tied to dst reg.
+ LIS->removeInterval(DstReg);
+ LIS->createAndComputeVirtRegInterval(DstReg);
+ LIS->createAndComputeVirtRegInterval(CopyReg);
+ if (ExecModified)
+ LIS->createAndComputeVirtRegInterval(SaveReg);
+
+ // Let this be recomputed.
+ LIS->removeRegUnit(*MCRegUnitIterator(AMDGPU::EXEC, TRI));
+}
+
+void SILowerControlFlow::emitBreak(MachineInstr &MI) {
+ MachineBasicBlock &MBB = *MI.getParent();
+ const DebugLoc &DL = MI.getDebugLoc();
+ unsigned Dst = MI.getOperand(0).getReg();
+
+ MachineInstr *Or = BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_OR_B64), Dst)
+ .addReg(AMDGPU::EXEC)
+ .add(MI.getOperand(1));
+
+ if (LIS)
+ LIS->ReplaceMachineInstrInMaps(MI, *Or);
+ MI.eraseFromParent();
+}
+
+void SILowerControlFlow::emitIfBreak(MachineInstr &MI) {
+ MI.setDesc(TII->get(AMDGPU::S_OR_B64));
+}
+
+void SILowerControlFlow::emitElseBreak(MachineInstr &MI) {
+ MI.setDesc(TII->get(AMDGPU::S_OR_B64));
+}
+
+void SILowerControlFlow::emitLoop(MachineInstr &MI) {
+ MachineBasicBlock &MBB = *MI.getParent();
+ const DebugLoc &DL = MI.getDebugLoc();
+
+ MachineInstr *AndN2 =
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_ANDN2_B64_term), AMDGPU::EXEC)
+ .addReg(AMDGPU::EXEC)
+ .add(MI.getOperand(0));
+
+ MachineInstr *Branch =
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_CBRANCH_EXECNZ))
+ .add(MI.getOperand(1));
+
+ if (LIS) {
+ LIS->ReplaceMachineInstrInMaps(MI, *AndN2);
+ LIS->InsertMachineInstrInMaps(*Branch);
+ }
+
+ MI.eraseFromParent();
+}
+
+void SILowerControlFlow::emitEndCf(MachineInstr &MI) {
+ MachineBasicBlock &MBB = *MI.getParent();
+ const DebugLoc &DL = MI.getDebugLoc();
+
+ MachineBasicBlock::iterator InsPt = MBB.begin();
+ MachineInstr *NewMI =
+ BuildMI(MBB, InsPt, DL, TII->get(AMDGPU::S_OR_B64), AMDGPU::EXEC)
+ .addReg(AMDGPU::EXEC)
+ .add(MI.getOperand(0));
+
+ if (LIS)
+ LIS->ReplaceMachineInstrInMaps(MI, *NewMI);
+
+ MI.eraseFromParent();
+
+ if (LIS)
+ LIS->handleMove(*NewMI);
+}
+
+// Returns replace operands for a logical operation, either single result
+// for exec or two operands if source was another equivalent operation.
+void SILowerControlFlow::findMaskOperands(MachineInstr &MI, unsigned OpNo,
+ SmallVectorImpl<MachineOperand> &Src) const {
+ MachineOperand &Op = MI.getOperand(OpNo);
+ if (!Op.isReg() || !TargetRegisterInfo::isVirtualRegister(Op.getReg())) {
+ Src.push_back(Op);
+ return;
+ }
+
+ MachineInstr *Def = MRI->getUniqueVRegDef(Op.getReg());
+ if (!Def || Def->getParent() != MI.getParent() ||
+ !(Def->isFullCopy() || (Def->getOpcode() == MI.getOpcode())))
+ return;
+
+ // Make sure we do not modify exec between def and use.
+ // A copy with implcitly defined exec inserted earlier is an exclusion, it
+ // does not really modify exec.
+ for (auto I = Def->getIterator(); I != MI.getIterator(); ++I)
+ if (I->modifiesRegister(AMDGPU::EXEC, TRI) &&
+ !(I->isCopy() && I->getOperand(0).getReg() != AMDGPU::EXEC))
+ return;
+
+ for (const auto &SrcOp : Def->explicit_operands())
+ if (SrcOp.isUse() && (!SrcOp.isReg() ||
+ TargetRegisterInfo::isVirtualRegister(SrcOp.getReg()) ||
+ SrcOp.getReg() == AMDGPU::EXEC))
+ Src.push_back(SrcOp);
+}
+
+// Search and combine pairs of equivalent instructions, like
+// S_AND_B64 x, (S_AND_B64 x, y) => S_AND_B64 x, y
+// S_OR_B64 x, (S_OR_B64 x, y) => S_OR_B64 x, y
+// One of the operands is exec mask.
+void SILowerControlFlow::combineMasks(MachineInstr &MI) {
+ assert(MI.getNumExplicitOperands() == 3);
+ SmallVector<MachineOperand, 4> Ops;
+ unsigned OpToReplace = 1;
+ findMaskOperands(MI, 1, Ops);
+ if (Ops.size() == 1) OpToReplace = 2; // First operand can be exec or its copy
+ findMaskOperands(MI, 2, Ops);
+ if (Ops.size() != 3) return;
+
+ unsigned UniqueOpndIdx;
+ if (Ops[0].isIdenticalTo(Ops[1])) UniqueOpndIdx = 2;
+ else if (Ops[0].isIdenticalTo(Ops[2])) UniqueOpndIdx = 1;
+ else if (Ops[1].isIdenticalTo(Ops[2])) UniqueOpndIdx = 1;
+ else return;
+
+ unsigned Reg = MI.getOperand(OpToReplace).getReg();
+ MI.RemoveOperand(OpToReplace);
+ MI.addOperand(Ops[UniqueOpndIdx]);
+ if (MRI->use_empty(Reg))
+ MRI->getUniqueVRegDef(Reg)->eraseFromParent();
+}
+
+bool SILowerControlFlow::runOnMachineFunction(MachineFunction &MF) {
+ const SISubtarget &ST = MF.getSubtarget<SISubtarget>();
+ TII = ST.getInstrInfo();
+ TRI = &TII->getRegisterInfo();
+
+ // This doesn't actually need LiveIntervals, but we can preserve them.
+ LIS = getAnalysisIfAvailable<LiveIntervals>();
+ MRI = &MF.getRegInfo();
+
+ MachineFunction::iterator NextBB;
+ for (MachineFunction::iterator BI = MF.begin(), BE = MF.end();
+ BI != BE; BI = NextBB) {
+ NextBB = std::next(BI);
+ MachineBasicBlock &MBB = *BI;
+
+ MachineBasicBlock::iterator I, Next, Last;
+
+ for (I = MBB.begin(), Last = MBB.end(); I != MBB.end(); I = Next) {
+ Next = std::next(I);
+ MachineInstr &MI = *I;
+
+ switch (MI.getOpcode()) {
+ case AMDGPU::SI_IF:
+ emitIf(MI);
+ break;
+
+ case AMDGPU::SI_ELSE:
+ emitElse(MI);
+ break;
+
+ case AMDGPU::SI_BREAK:
+ emitBreak(MI);
+ break;
+
+ case AMDGPU::SI_IF_BREAK:
+ emitIfBreak(MI);
+ break;
+
+ case AMDGPU::SI_ELSE_BREAK:
+ emitElseBreak(MI);
+ break;
+
+ case AMDGPU::SI_LOOP:
+ emitLoop(MI);
+ break;
+
+ case AMDGPU::SI_END_CF:
+ emitEndCf(MI);
+ break;
+
+ case AMDGPU::S_AND_B64:
+ case AMDGPU::S_OR_B64:
+ // Cleanup bit manipulations on exec mask
+ combineMasks(MI);
+ Last = I;
+ continue;
+
+ default:
+ Last = I;
+ continue;
+ }
+
+ // Replay newly inserted code to combine masks
+ Next = (Last == MBB.end()) ? MBB.begin() : Last;
+ }
+ }
+
+ return true;
+}
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