/// %vreg3 <vsrc> = COPY %vreg2 <vgpr>
/// BB2:
/// %vreg4 <vsrc> = PHI %vreg1 <vsrc>, <BB#0>, %vreg3 <vrsc>, <BB#1>
-/// %vreg5 <vgpr> = VECTOR_INST %vreg4 <vsrc>
+/// %vreg5 <vgpr> = VECTOR_INST %vreg4 <vsrc>
+///
///
-///
/// The coalescer will begin at BB0 and eliminate its copy, then the resulting
/// code will look like this:
///
/// Now that the result of the PHI instruction is an SGPR, the register
/// allocator is now forced to constrain the register class of %vreg3 to
/// <sgpr> so we end up with final code like this:
-///
+///
/// BB0:
/// %vreg0 <sgpr> = SCALAR_INST
/// ...
/// %vreg4 <sgpr> = PHI %vreg0 <sgpr>, <BB#0>, %vreg3 <sgpr>, <BB#1>
/// %vreg5 <vgpr> = VECTOR_INST %vreg4 <sgpr>
///
-/// Now this code contains an illegal copy from a VGPR to an SGPR.
+/// Now this code contains an illegal copy from a VGPR to an SGPR.
///
/// In order to avoid this problem, this pass searches for PHI instructions
/// which define a <vsrc> register and constrains its definition class to
//===----------------------------------------------------------------------===//
#include "AMDGPU.h"
+#include "AMDGPUSubtarget.h"
#include "SIInstrInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
using namespace llvm;
+#define DEBUG_TYPE "sgpr-copies"
+
namespace {
class SIFixSGPRCopies : public MachineFunctionPass {
private:
static char ID;
- const TargetRegisterClass *inferRegClass(const TargetRegisterInfo *TRI,
+ const TargetRegisterClass *inferRegClassFromUses(const SIRegisterInfo *TRI,
const MachineRegisterInfo &MRI,
- unsigned Reg) const;
+ unsigned Reg,
+ unsigned SubReg) const;
+ const TargetRegisterClass *inferRegClassFromDef(const SIRegisterInfo *TRI,
+ const MachineRegisterInfo &MRI,
+ unsigned Reg,
+ unsigned SubReg) const;
+ bool isVGPRToSGPRCopy(const MachineInstr &Copy, const SIRegisterInfo *TRI,
+ const MachineRegisterInfo &MRI) const;
public:
SIFixSGPRCopies(TargetMachine &tm) : MachineFunctionPass(ID) { }
- virtual bool runOnMachineFunction(MachineFunction &MF);
+ bool runOnMachineFunction(MachineFunction &MF) override;
- const char *getPassName() const {
+ const char *getPassName() const override {
return "SI Fix SGPR copies";
}
return new SIFixSGPRCopies(tm);
}
-/// This functions walks the use/def chains starting with the definition of
-/// \p Reg until it finds an Instruction that isn't a COPY returns
-/// the register class of that instruction.
-const TargetRegisterClass *SIFixSGPRCopies::inferRegClass(
- const TargetRegisterInfo *TRI,
+static bool hasVGPROperands(const MachineInstr &MI, const SIRegisterInfo *TRI) {
+ const MachineRegisterInfo &MRI = MI.getParent()->getParent()->getRegInfo();
+ for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
+ if (!MI.getOperand(i).isReg() ||
+ !TargetRegisterInfo::isVirtualRegister(MI.getOperand(i).getReg()))
+ continue;
+
+ if (TRI->hasVGPRs(MRI.getRegClass(MI.getOperand(i).getReg())))
+ return true;
+ }
+ return false;
+}
+
+/// This functions walks the use list of Reg until it finds an Instruction
+/// that isn't a COPY returns the register class of that instruction.
+/// \return The register defined by the first non-COPY instruction.
+const TargetRegisterClass *SIFixSGPRCopies::inferRegClassFromUses(
+ const SIRegisterInfo *TRI,
const MachineRegisterInfo &MRI,
- unsigned Reg) const {
+ unsigned Reg,
+ unsigned SubReg) const {
// The Reg parameter to the function must always be defined by either a PHI
// or a COPY, therefore it cannot be a physical register.
assert(TargetRegisterInfo::isVirtualRegister(Reg) &&
"Reg cannot be a physical register");
const TargetRegisterClass *RC = MRI.getRegClass(Reg);
- for (MachineRegisterInfo::use_iterator I = MRI.use_begin(Reg),
- E = MRI.use_end(); I != E; ++I) {
+ RC = TRI->getSubRegClass(RC, SubReg);
+ for (MachineRegisterInfo::use_instr_iterator
+ I = MRI.use_instr_begin(Reg), E = MRI.use_instr_end(); I != E; ++I) {
switch (I->getOpcode()) {
case AMDGPU::COPY:
- RC = TRI->getCommonSubClass(RC, inferRegClass(TRI, MRI,
- I->getOperand(0).getReg()));
+ RC = TRI->getCommonSubClass(RC, inferRegClassFromUses(TRI, MRI,
+ I->getOperand(0).getReg(),
+ I->getOperand(0).getSubReg()));
break;
}
}
return RC;
}
+const TargetRegisterClass *SIFixSGPRCopies::inferRegClassFromDef(
+ const SIRegisterInfo *TRI,
+ const MachineRegisterInfo &MRI,
+ unsigned Reg,
+ unsigned SubReg) const {
+ if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
+ const TargetRegisterClass *RC = TRI->getPhysRegClass(Reg);
+ return TRI->getSubRegClass(RC, SubReg);
+ }
+ MachineInstr *Def = MRI.getVRegDef(Reg);
+ if (Def->getOpcode() != AMDGPU::COPY) {
+ return TRI->getSubRegClass(MRI.getRegClass(Reg), SubReg);
+ }
+
+ return inferRegClassFromDef(TRI, MRI, Def->getOperand(1).getReg(),
+ Def->getOperand(1).getSubReg());
+}
+
+bool SIFixSGPRCopies::isVGPRToSGPRCopy(const MachineInstr &Copy,
+ const SIRegisterInfo *TRI,
+ const MachineRegisterInfo &MRI) const {
+
+ unsigned DstReg = Copy.getOperand(0).getReg();
+ unsigned SrcReg = Copy.getOperand(1).getReg();
+ unsigned SrcSubReg = Copy.getOperand(1).getSubReg();
+ const TargetRegisterClass *DstRC = MRI.getRegClass(DstReg);
+ const TargetRegisterClass *SrcRC;
+
+ if (!TargetRegisterInfo::isVirtualRegister(SrcReg) ||
+ DstRC == &AMDGPU::M0RegRegClass ||
+ MRI.getRegClass(SrcReg) == &AMDGPU::VReg_1RegClass)
+ return false;
+
+ SrcRC = TRI->getSubRegClass(MRI.getRegClass(SrcReg), SrcSubReg);
+ return TRI->isSGPRClass(DstRC) && TRI->hasVGPRs(SrcRC);
+}
+
bool SIFixSGPRCopies::runOnMachineFunction(MachineFunction &MF) {
MachineRegisterInfo &MRI = MF.getRegInfo();
- const TargetRegisterInfo *TRI = MF.getTarget().getRegisterInfo();
+ const SIRegisterInfo *TRI =
+ static_cast<const SIRegisterInfo *>(MF.getSubtarget().getRegisterInfo());
+ const SIInstrInfo *TII =
+ static_cast<const SIInstrInfo *>(MF.getSubtarget().getInstrInfo());
for (MachineFunction::iterator BI = MF.begin(), BE = MF.end();
BI != BE; ++BI) {
for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
I != E; ++I) {
MachineInstr &MI = *I;
- if (MI.getOpcode() != AMDGPU::PHI) {
- continue;
+ if (MI.getOpcode() == AMDGPU::COPY && isVGPRToSGPRCopy(MI, TRI, MRI)) {
+ DEBUG(dbgs() << "Fixing VGPR -> SGPR copy:\n");
+ DEBUG(MI.print(dbgs()));
+ TII->moveToVALU(MI);
+
+ }
+
+ switch (MI.getOpcode()) {
+ default: continue;
+ case AMDGPU::PHI: {
+ DEBUG(dbgs() << " Fixing PHI:\n");
+ DEBUG(MI.print(dbgs()));
+
+ for (unsigned i = 1; i < MI.getNumOperands(); i+=2) {
+ unsigned Reg = MI.getOperand(i).getReg();
+ const TargetRegisterClass *RC = inferRegClassFromDef(TRI, MRI, Reg,
+ MI.getOperand(0).getSubReg());
+ MRI.constrainRegClass(Reg, RC);
+ }
+ unsigned Reg = MI.getOperand(0).getReg();
+ const TargetRegisterClass *RC = inferRegClassFromUses(TRI, MRI, Reg,
+ MI.getOperand(0).getSubReg());
+ if (TRI->getCommonSubClass(RC, &AMDGPU::VReg_32RegClass)) {
+ MRI.constrainRegClass(Reg, &AMDGPU::VReg_32RegClass);
+ }
+
+ if (!TRI->isSGPRClass(MRI.getRegClass(Reg)))
+ break;
+
+ // If a PHI node defines an SGPR and any of its operands are VGPRs,
+ // then we need to move it to the VALU.
+ //
+ // Also, if a PHI node defines an SGPR and has all SGPR operands
+ // we must move it to the VALU, because the SGPR operands will
+ // all end up being assigned the same register, which means
+ // there is a potential for a conflict if different threads take
+ // different control flow paths.
+ //
+ // For Example:
+ //
+ // sgpr0 = def;
+ // ...
+ // sgpr1 = def;
+ // ...
+ // sgpr2 = PHI sgpr0, sgpr1
+ // use sgpr2;
+ //
+ // Will Become:
+ //
+ // sgpr2 = def;
+ // ...
+ // sgpr2 = def;
+ // ...
+ // use sgpr2
+ //
+ // FIXME: This is OK if the branching decision is made based on an
+ // SGPR value.
+ bool SGPRBranch = false;
+
+ // The one exception to this rule is when one of the operands
+ // is defined by a SI_BREAK, SI_IF_BREAK, or SI_ELSE_BREAK
+ // instruction. In this case, there we know the program will
+ // never enter the second block (the loop) without entering
+ // the first block (where the condition is computed), so there
+ // is no chance for values to be over-written.
+
+ bool HasBreakDef = false;
+ for (unsigned i = 1; i < MI.getNumOperands(); i+=2) {
+ unsigned Reg = MI.getOperand(i).getReg();
+ if (TRI->hasVGPRs(MRI.getRegClass(Reg))) {
+ TII->moveToVALU(MI);
+ break;
+ }
+ MachineInstr *DefInstr = MRI.getUniqueVRegDef(Reg);
+ assert(DefInstr);
+ switch(DefInstr->getOpcode()) {
+
+ case AMDGPU::SI_BREAK:
+ case AMDGPU::SI_IF_BREAK:
+ case AMDGPU::SI_ELSE_BREAK:
+ // If we see a PHI instruction that defines an SGPR, then that PHI
+ // instruction has already been considered and should have
+ // a *_BREAK as an operand.
+ case AMDGPU::PHI:
+ HasBreakDef = true;
+ break;
+ }
+ }
+
+ if (!SGPRBranch && !HasBreakDef)
+ TII->moveToVALU(MI);
+ break;
+ }
+ case AMDGPU::REG_SEQUENCE: {
+ if (TRI->hasVGPRs(TII->getOpRegClass(MI, 0)) ||
+ !hasVGPROperands(MI, TRI))
+ continue;
+
+ DEBUG(dbgs() << "Fixing REG_SEQUENCE: " << MI);
+
+ TII->moveToVALU(MI);
+ break;
+ }
+ case AMDGPU::INSERT_SUBREG: {
+ const TargetRegisterClass *DstRC, *Src0RC, *Src1RC;
+ DstRC = MRI.getRegClass(MI.getOperand(0).getReg());
+ Src0RC = MRI.getRegClass(MI.getOperand(1).getReg());
+ Src1RC = MRI.getRegClass(MI.getOperand(2).getReg());
+ if (TRI->isSGPRClass(DstRC) &&
+ (TRI->hasVGPRs(Src0RC) || TRI->hasVGPRs(Src1RC))) {
+ DEBUG(dbgs() << " Fixing INSERT_SUBREG: " << MI);
+ TII->moveToVALU(MI);
+ }
+ break;
}
- unsigned Reg = MI.getOperand(0).getReg();
- const TargetRegisterClass *RC = inferRegClass(TRI, MRI, Reg);
- if (TRI->getCommonSubClass(RC, &AMDGPU::VReg_32RegClass)) {
- MRI.constrainRegClass(Reg, &AMDGPU::VReg_32RegClass);
}
}
}
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