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-rw-r--r--lib/Target/R600/SILowerControlFlow.cpp501
1 files changed, 501 insertions, 0 deletions
diff --git a/lib/Target/R600/SILowerControlFlow.cpp b/lib/Target/R600/SILowerControlFlow.cpp
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index 000000000000..2b60eb9fb375
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+++ b/lib/Target/R600/SILowerControlFlow.cpp
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+//===-- 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 "SIInstrInfo.h"
+#include "SIMachineFunctionInfo.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+
+using namespace llvm;
+
+namespace {
+
+class SILowerControlFlowPass : public MachineFunctionPass {
+
+private:
+ static const unsigned SkipThreshold = 12;
+
+ static char ID;
+ const TargetRegisterInfo *TRI;
+ const TargetInstrInfo *TII;
+
+ bool shouldSkip(MachineBasicBlock *From, MachineBasicBlock *To);
+
+ void Skip(MachineInstr &From, MachineOperand &To);
+ void SkipIfDead(MachineInstr &MI);
+
+ void If(MachineInstr &MI);
+ void Else(MachineInstr &MI);
+ void Break(MachineInstr &MI);
+ void IfBreak(MachineInstr &MI);
+ void ElseBreak(MachineInstr &MI);
+ void Loop(MachineInstr &MI);
+ void EndCf(MachineInstr &MI);
+
+ void Kill(MachineInstr &MI);
+ void Branch(MachineInstr &MI);
+
+ void LoadM0(MachineInstr &MI, MachineInstr *MovRel);
+ void IndirectSrc(MachineInstr &MI);
+ void IndirectDst(MachineInstr &MI);
+
+public:
+ SILowerControlFlowPass(TargetMachine &tm) :
+ MachineFunctionPass(ID), TRI(tm.getRegisterInfo()),
+ TII(tm.getInstrInfo()) { }
+
+ virtual bool runOnMachineFunction(MachineFunction &MF);
+
+ const char *getPassName() const {
+ return "SI Lower control flow instructions";
+ }
+
+};
+
+} // End anonymous namespace
+
+char SILowerControlFlowPass::ID = 0;
+
+FunctionPass *llvm::createSILowerControlFlowPass(TargetMachine &tm) {
+ return new SILowerControlFlowPass(tm);
+}
+
+bool SILowerControlFlowPass::shouldSkip(MachineBasicBlock *From,
+ MachineBasicBlock *To) {
+
+ unsigned NumInstr = 0;
+
+ for (MachineBasicBlock *MBB = From; MBB != To && !MBB->succ_empty();
+ MBB = *MBB->succ_begin()) {
+
+ for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
+ NumInstr < SkipThreshold && I != E; ++I) {
+
+ if (I->isBundle() || !I->isBundled())
+ if (++NumInstr >= SkipThreshold)
+ return true;
+ }
+ }
+
+ return false;
+}
+
+void SILowerControlFlowPass::Skip(MachineInstr &From, MachineOperand &To) {
+
+ if (!shouldSkip(*From.getParent()->succ_begin(), To.getMBB()))
+ return;
+
+ DebugLoc DL = From.getDebugLoc();
+ BuildMI(*From.getParent(), &From, DL, TII->get(AMDGPU::S_CBRANCH_EXECZ))
+ .addOperand(To)
+ .addReg(AMDGPU::EXEC);
+}
+
+void SILowerControlFlowPass::SkipIfDead(MachineInstr &MI) {
+
+ MachineBasicBlock &MBB = *MI.getParent();
+ DebugLoc DL = MI.getDebugLoc();
+
+ if (!shouldSkip(&MBB, &MBB.getParent()->back()))
+ return;
+
+ MachineBasicBlock::iterator Insert = &MI;
+ ++Insert;
+
+ // If the exec mask is non-zero, skip the next two instructions
+ BuildMI(MBB, Insert, DL, TII->get(AMDGPU::S_CBRANCH_EXECNZ))
+ .addImm(3)
+ .addReg(AMDGPU::EXEC);
+
+ // Exec mask is zero: Export to NULL target...
+ BuildMI(MBB, Insert, DL, TII->get(AMDGPU::EXP))
+ .addImm(0)
+ .addImm(0x09) // V_008DFC_SQ_EXP_NULL
+ .addImm(0)
+ .addImm(1)
+ .addImm(1)
+ .addReg(AMDGPU::VGPR0)
+ .addReg(AMDGPU::VGPR0)
+ .addReg(AMDGPU::VGPR0)
+ .addReg(AMDGPU::VGPR0);
+
+ // ... and terminate wavefront
+ BuildMI(MBB, Insert, DL, TII->get(AMDGPU::S_ENDPGM));
+}
+
+void SILowerControlFlowPass::If(MachineInstr &MI) {
+ MachineBasicBlock &MBB = *MI.getParent();
+ DebugLoc DL = MI.getDebugLoc();
+ unsigned Reg = MI.getOperand(0).getReg();
+ unsigned Vcc = MI.getOperand(1).getReg();
+
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_AND_SAVEEXEC_B64), Reg)
+ .addReg(Vcc);
+
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_XOR_B64), Reg)
+ .addReg(AMDGPU::EXEC)
+ .addReg(Reg);
+
+ Skip(MI, MI.getOperand(2));
+
+ MI.eraseFromParent();
+}
+
+void SILowerControlFlowPass::Else(MachineInstr &MI) {
+ MachineBasicBlock &MBB = *MI.getParent();
+ DebugLoc DL = MI.getDebugLoc();
+ unsigned Dst = MI.getOperand(0).getReg();
+ unsigned Src = MI.getOperand(1).getReg();
+
+ BuildMI(MBB, MBB.getFirstNonPHI(), DL,
+ TII->get(AMDGPU::S_OR_SAVEEXEC_B64), Dst)
+ .addReg(Src); // Saved EXEC
+
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_XOR_B64), AMDGPU::EXEC)
+ .addReg(AMDGPU::EXEC)
+ .addReg(Dst);
+
+ Skip(MI, MI.getOperand(2));
+
+ MI.eraseFromParent();
+}
+
+void SILowerControlFlowPass::Break(MachineInstr &MI) {
+ MachineBasicBlock &MBB = *MI.getParent();
+ DebugLoc DL = MI.getDebugLoc();
+
+ unsigned Dst = MI.getOperand(0).getReg();
+ unsigned Src = MI.getOperand(1).getReg();
+
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_OR_B64), Dst)
+ .addReg(AMDGPU::EXEC)
+ .addReg(Src);
+
+ MI.eraseFromParent();
+}
+
+void SILowerControlFlowPass::IfBreak(MachineInstr &MI) {
+ MachineBasicBlock &MBB = *MI.getParent();
+ DebugLoc DL = MI.getDebugLoc();
+
+ unsigned Dst = MI.getOperand(0).getReg();
+ unsigned Vcc = MI.getOperand(1).getReg();
+ unsigned Src = MI.getOperand(2).getReg();
+
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_OR_B64), Dst)
+ .addReg(Vcc)
+ .addReg(Src);
+
+ MI.eraseFromParent();
+}
+
+void SILowerControlFlowPass::ElseBreak(MachineInstr &MI) {
+ MachineBasicBlock &MBB = *MI.getParent();
+ DebugLoc DL = MI.getDebugLoc();
+
+ unsigned Dst = MI.getOperand(0).getReg();
+ unsigned Saved = MI.getOperand(1).getReg();
+ unsigned Src = MI.getOperand(2).getReg();
+
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_OR_B64), Dst)
+ .addReg(Saved)
+ .addReg(Src);
+
+ MI.eraseFromParent();
+}
+
+void SILowerControlFlowPass::Loop(MachineInstr &MI) {
+ MachineBasicBlock &MBB = *MI.getParent();
+ DebugLoc DL = MI.getDebugLoc();
+ unsigned Src = MI.getOperand(0).getReg();
+
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_ANDN2_B64), AMDGPU::EXEC)
+ .addReg(AMDGPU::EXEC)
+ .addReg(Src);
+
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_CBRANCH_EXECNZ))
+ .addOperand(MI.getOperand(1))
+ .addReg(AMDGPU::EXEC);
+
+ MI.eraseFromParent();
+}
+
+void SILowerControlFlowPass::EndCf(MachineInstr &MI) {
+ MachineBasicBlock &MBB = *MI.getParent();
+ DebugLoc DL = MI.getDebugLoc();
+ unsigned Reg = MI.getOperand(0).getReg();
+
+ BuildMI(MBB, MBB.getFirstNonPHI(), DL,
+ TII->get(AMDGPU::S_OR_B64), AMDGPU::EXEC)
+ .addReg(AMDGPU::EXEC)
+ .addReg(Reg);
+
+ MI.eraseFromParent();
+}
+
+void SILowerControlFlowPass::Branch(MachineInstr &MI) {
+ MachineBasicBlock *Next = MI.getParent()->getNextNode();
+ MachineBasicBlock *Target = MI.getOperand(0).getMBB();
+ if (Target == Next)
+ MI.eraseFromParent();
+ else
+ assert(0);
+}
+
+void SILowerControlFlowPass::Kill(MachineInstr &MI) {
+
+ MachineBasicBlock &MBB = *MI.getParent();
+ DebugLoc DL = MI.getDebugLoc();
+
+ // Kill is only allowed in pixel shaders
+ assert(MBB.getParent()->getInfo<SIMachineFunctionInfo>()->ShaderType ==
+ ShaderType::PIXEL);
+
+ // Clear this pixel from the exec mask if the operand is negative
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::V_CMPX_LE_F32_e32), AMDGPU::VCC)
+ .addImm(0)
+ .addOperand(MI.getOperand(0));
+
+ MI.eraseFromParent();
+}
+
+void SILowerControlFlowPass::LoadM0(MachineInstr &MI, MachineInstr *MovRel) {
+
+ MachineBasicBlock &MBB = *MI.getParent();
+ DebugLoc DL = MI.getDebugLoc();
+ MachineBasicBlock::iterator I = MI;
+
+ unsigned Save = MI.getOperand(1).getReg();
+ unsigned Idx = MI.getOperand(3).getReg();
+
+ if (AMDGPU::SReg_32RegClass.contains(Idx)) {
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_MOV_B32), AMDGPU::M0)
+ .addReg(Idx);
+ MBB.insert(I, MovRel);
+ MI.eraseFromParent();
+ return;
+ }
+
+ assert(AMDGPU::SReg_64RegClass.contains(Save));
+ assert(AMDGPU::VReg_32RegClass.contains(Idx));
+
+ // Save the EXEC mask
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_MOV_B64), Save)
+ .addReg(AMDGPU::EXEC);
+
+ // Read the next variant into VCC (lower 32 bits) <- also loop target
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::V_READFIRSTLANE_B32_e32), AMDGPU::VCC)
+ .addReg(Idx);
+
+ // Move index from VCC into M0
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_MOV_B32), AMDGPU::M0)
+ .addReg(AMDGPU::VCC);
+
+ // Compare the just read M0 value to all possible Idx values
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::V_CMP_EQ_U32_e32), AMDGPU::VCC)
+ .addReg(AMDGPU::M0)
+ .addReg(Idx);
+
+ // Update EXEC, save the original EXEC value to VCC
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_AND_SAVEEXEC_B64), AMDGPU::VCC)
+ .addReg(AMDGPU::VCC);
+
+ // Do the actual move
+ MBB.insert(I, MovRel);
+
+ // Update EXEC, switch all done bits to 0 and all todo bits to 1
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_XOR_B64), AMDGPU::EXEC)
+ .addReg(AMDGPU::EXEC)
+ .addReg(AMDGPU::VCC);
+
+ // Loop back to V_READFIRSTLANE_B32 if there are still variants to cover
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_CBRANCH_EXECNZ))
+ .addImm(-7)
+ .addReg(AMDGPU::EXEC);
+
+ // Restore EXEC
+ BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_MOV_B64), AMDGPU::EXEC)
+ .addReg(Save);
+
+ MI.eraseFromParent();
+}
+
+void SILowerControlFlowPass::IndirectSrc(MachineInstr &MI) {
+
+ MachineBasicBlock &MBB = *MI.getParent();
+ DebugLoc DL = MI.getDebugLoc();
+
+ unsigned Dst = MI.getOperand(0).getReg();
+ unsigned Vec = MI.getOperand(2).getReg();
+ unsigned Off = MI.getOperand(4).getImm();
+
+ MachineInstr *MovRel =
+ BuildMI(*MBB.getParent(), DL, TII->get(AMDGPU::V_MOVRELS_B32_e32), Dst)
+ .addReg(TRI->getSubReg(Vec, AMDGPU::sub0) + Off)
+ .addReg(AMDGPU::M0, RegState::Implicit)
+ .addReg(Vec, RegState::Implicit);
+
+ LoadM0(MI, MovRel);
+}
+
+void SILowerControlFlowPass::IndirectDst(MachineInstr &MI) {
+
+ MachineBasicBlock &MBB = *MI.getParent();
+ DebugLoc DL = MI.getDebugLoc();
+
+ unsigned Dst = MI.getOperand(0).getReg();
+ unsigned Off = MI.getOperand(4).getImm();
+ unsigned Val = MI.getOperand(5).getReg();
+
+ MachineInstr *MovRel =
+ BuildMI(*MBB.getParent(), DL, TII->get(AMDGPU::V_MOVRELD_B32_e32))
+ .addReg(TRI->getSubReg(Dst, AMDGPU::sub0) + Off, RegState::Define)
+ .addReg(Val)
+ .addReg(AMDGPU::M0, RegState::Implicit)
+ .addReg(Dst, RegState::Implicit);
+
+ LoadM0(MI, MovRel);
+}
+
+bool SILowerControlFlowPass::runOnMachineFunction(MachineFunction &MF) {
+
+ bool HaveKill = false;
+ bool NeedWQM = false;
+ unsigned Depth = 0;
+
+ for (MachineFunction::iterator BI = MF.begin(), BE = MF.end();
+ BI != BE; ++BI) {
+
+ MachineBasicBlock &MBB = *BI;
+ for (MachineBasicBlock::iterator I = MBB.begin(), Next = llvm::next(I);
+ I != MBB.end(); I = Next) {
+
+ Next = llvm::next(I);
+ MachineInstr &MI = *I;
+ switch (MI.getOpcode()) {
+ default: break;
+ case AMDGPU::SI_IF:
+ ++Depth;
+ If(MI);
+ break;
+
+ case AMDGPU::SI_ELSE:
+ Else(MI);
+ break;
+
+ case AMDGPU::SI_BREAK:
+ Break(MI);
+ break;
+
+ case AMDGPU::SI_IF_BREAK:
+ IfBreak(MI);
+ break;
+
+ case AMDGPU::SI_ELSE_BREAK:
+ ElseBreak(MI);
+ break;
+
+ case AMDGPU::SI_LOOP:
+ ++Depth;
+ Loop(MI);
+ break;
+
+ case AMDGPU::SI_END_CF:
+ if (--Depth == 0 && HaveKill) {
+ SkipIfDead(MI);
+ HaveKill = false;
+ }
+ EndCf(MI);
+ break;
+
+ case AMDGPU::SI_KILL:
+ if (Depth == 0)
+ SkipIfDead(MI);
+ else
+ HaveKill = true;
+ Kill(MI);
+ break;
+
+ case AMDGPU::S_BRANCH:
+ Branch(MI);
+ break;
+
+ case AMDGPU::SI_INDIRECT_SRC:
+ IndirectSrc(MI);
+ break;
+
+ case AMDGPU::SI_INDIRECT_DST_V2:
+ case AMDGPU::SI_INDIRECT_DST_V4:
+ case AMDGPU::SI_INDIRECT_DST_V8:
+ case AMDGPU::SI_INDIRECT_DST_V16:
+ IndirectDst(MI);
+ break;
+
+ case AMDGPU::V_INTERP_P1_F32:
+ case AMDGPU::V_INTERP_P2_F32:
+ case AMDGPU::V_INTERP_MOV_F32:
+ NeedWQM = true;
+ break;
+
+ }
+ }
+ }
+
+ if (NeedWQM) {
+ MachineBasicBlock &MBB = MF.front();
+ BuildMI(MBB, MBB.getFirstNonPHI(), DebugLoc(), TII->get(AMDGPU::S_WQM_B64),
+ AMDGPU::EXEC).addReg(AMDGPU::EXEC);
+ }
+
+ return true;
+}
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