[PowerPC] Initial support for the VSX instruction set

VSX is an ISA extension supported on the POWER7 and later cores that enhances
floating-point vector and scalar capabilities. Among other things, this adds
<2 x double> support and generally helps to reduce register pressure.

The interesting part of this ISA feature is the register configuration: there
are 64 new 128-bit vector registers, the 32 of which are super-registers of the
existing 32 scalar floating-point registers, and the second 32 of which overlap
with the 32 Altivec vector registers. This makes things like vector insertion
and extraction tricky: this can be free but only if we force a restriction to
the right register subclass when needed. A new "minipass" PPCVSXCopy takes care
of this (although it could do a more-optimal job of it; see the comment about
unnecessary copies below).

Please note that, currently, VSX is not enabled by default when targeting
anything because it is not yet ready for that.  The assembler and disassembler
are fully implemented and tested. However:

 - CodeGen support causes miscompiles; test-suite runtime failures:
      MultiSource/Benchmarks/FreeBench/distray/distray
      MultiSource/Benchmarks/McCat/08-main/main
      MultiSource/Benchmarks/Olden/voronoi/voronoi
      MultiSource/Benchmarks/mafft/pairlocalalign
      MultiSource/Benchmarks/tramp3d-v4/tramp3d-v4
      SingleSource/Benchmarks/CoyoteBench/almabench
      SingleSource/Benchmarks/Misc/matmul_f64_4x4

 - The lowering currently falls back to using Altivec instructions far more
   than it should. Worse, there are some things that are scalarized through the
   stack that shouldn't be.

 - A lot of unnecessary copies make it past the optimizers, and this needs to
   be fixed.

 - Many more regression tests are needed.

Normally, I'd fix these things prior to committing, but there are some
students and other contributors who would like to work this, and so it makes
sense to move this development process upstream where it can be subject to the
regular code-review procedures.

llvm-svn: 203768

1 files changed, 199 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
index d9907a0..408dd06 100644
--- a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
@@ -165,6 +165,7 @@ unsigned PPCInstrInfo::isLoadFromStackSlot(const MachineInstr *MI,
   case PPC::RESTORE_CR:
   case PPC::RESTORE_CRBIT:
   case PPC::LVX:
+  case PPC::LXVD2X:
   case PPC::RESTORE_VRSAVE:
     // Check for the operands added by addFrameReference (the immediate is the
     // offset which defaults to 0).
@@ -190,6 +191,7 @@ unsigned PPCInstrInfo::isStoreToStackSlot(const MachineInstr *MI,
   case PPC::SPILL_CR:
   case PPC::SPILL_CRBIT:
   case PPC::STVX:
+  case PPC::STXVD2X:
   case PPC::SPILL_VRSAVE:
     // Check for the operands added by addFrameReference (the immediate is the
     // offset which defaults to 0).
@@ -655,6 +657,47 @@ void PPCInstrInfo::copyPhysReg(MachineBasicBlock &MBB,
                                MachineBasicBlock::iterator I, DebugLoc DL,
                                unsigned DestReg, unsigned SrcReg,
                                bool KillSrc) const {
+  // We can end up with self copies and similar things as a result of VSX copy
+  // legalization. Promote (or just ignore) them here.
+  const TargetRegisterInfo *TRI = &getRegisterInfo();
+  if (PPC::F8RCRegClass.contains(DestReg) &&
+      PPC::VSLRCRegClass.contains(SrcReg)) {
+    unsigned SuperReg =
+      TRI->getMatchingSuperReg(DestReg, PPC::sub_64, &PPC::VSRCRegClass);
+
+    if (SrcReg == SuperReg)
+      return;
+
+    DestReg = SuperReg;
+  } else if (PPC::VRRCRegClass.contains(DestReg) &&
+             PPC::VSHRCRegClass.contains(SrcReg)) {
+    unsigned SuperReg =
+      TRI->getMatchingSuperReg(DestReg, PPC::sub_128, &PPC::VSRCRegClass);
+
+    if (SrcReg == SuperReg)
+      return;
+
+    DestReg = SuperReg;
+  } else if (PPC::F8RCRegClass.contains(SrcReg) &&
+             PPC::VSLRCRegClass.contains(DestReg)) {
+    unsigned SuperReg =
+      TRI->getMatchingSuperReg(SrcReg, PPC::sub_64, &PPC::VSRCRegClass);
+
+    if (DestReg == SuperReg)
+      return;
+
+    SrcReg = SuperReg;
+  } else if (PPC::VRRCRegClass.contains(SrcReg) &&
+             PPC::VSHRCRegClass.contains(DestReg)) {
+    unsigned SuperReg =
+      TRI->getMatchingSuperReg(SrcReg, PPC::sub_128, &PPC::VSRCRegClass);
+
+    if (DestReg == SuperReg)
+      return;
+
+    SrcReg = SuperReg;
+  }
+
   unsigned Opc;
   if (PPC::GPRCRegClass.contains(DestReg, SrcReg))
     Opc = PPC::OR;
@@ -666,6 +709,14 @@ void PPCInstrInfo::copyPhysReg(MachineBasicBlock &MBB,
     Opc = PPC::MCRF;
   else if (PPC::VRRCRegClass.contains(DestReg, SrcReg))
     Opc = PPC::VOR;
+  else if (PPC::VSRCRegClass.contains(DestReg, SrcReg))
+    // FIXME: There are really two different ways this can be done, and we
+    // should pick the better one depending on the situation:
+    //   1. xxlor : This has lower latency (on the P7), 2 cycles, but can only
+    //      issue in VSU pipeline 0.
+    //   2. xmovdp/xmovsp: This has higher latency (on the P7), 6 cycles, but
+    //      can go to either pipeline.
+    Opc = PPC::XXLOR;
   else if (PPC::CRBITRCRegClass.contains(DestReg, SrcReg))
     Opc = PPC::CROR;
   else
@@ -731,6 +782,12 @@ PPCInstrInfo::StoreRegToStackSlot(MachineFunction &MF,
                                                getKillRegState(isKill)),
                                        FrameIdx));
     NonRI = true;
+  } else if (PPC::VSRCRegClass.hasSubClassEq(RC)) {
+    NewMIs.push_back(addFrameReference(BuildMI(MF, DL, get(PPC::STXVD2X))
+                                       .addReg(SrcReg,
+                                               getKillRegState(isKill)),
+                                       FrameIdx));
+    NonRI = true;
   } else if (PPC::VRSAVERCRegClass.hasSubClassEq(RC)) {
     assert(TM.getSubtargetImpl()->isDarwin() &&
            "VRSAVE only needs spill/restore on Darwin");
@@ -818,6 +875,10 @@ PPCInstrInfo::LoadRegFromStackSlot(MachineFunction &MF, DebugLoc DL,
     NewMIs.push_back(addFrameReference(BuildMI(MF, DL, get(PPC::LVX), DestReg),
                                        FrameIdx));
     NonRI = true;
+  } else if (PPC::VSRCRegClass.hasSubClassEq(RC)) {
+    NewMIs.push_back(addFrameReference(BuildMI(MF, DL, get(PPC::LXVD2X), DestReg),
+                                       FrameIdx));
+    NonRI = true;
   } else if (PPC::VRSAVERCRegClass.hasSubClassEq(RC)) {
     assert(TM.getSubtargetImpl()->isDarwin() &&
            "VRSAVE only needs spill/restore on Darwin");
@@ -1485,6 +1546,144 @@ unsigned PPCInstrInfo::GetInstSizeInBytes(const MachineInstr *MI) const {
   }
 }
 
+
+#undef DEBUG_TYPE
+#define DEBUG_TYPE "ppc-vsx-copy"
+
+namespace llvm {
+  void initializePPCVSXCopyPass(PassRegistry&);
+}
+
+namespace {
+  // PPCVSXCopy pass - For copies between VSX registers and non-VSX registers
+  // (Altivec and scalar floating-point registers), we need to transform the
+  // copies into subregister copies with other restrictions.
+  struct PPCVSXCopy : public MachineFunctionPass {
+    static char ID;
+    PPCVSXCopy() : MachineFunctionPass(ID) {
+      initializePPCVSXCopyPass(*PassRegistry::getPassRegistry());
+    }
+
+    const PPCTargetMachine *TM;
+    const PPCInstrInfo *TII;
+
+    bool IsRegInClass(unsigned Reg, const TargetRegisterClass *RC,
+                      MachineRegisterInfo &MRI) {
+      if (TargetRegisterInfo::isVirtualRegister(Reg)) {
+        return RC->hasSubClassEq(MRI.getRegClass(Reg));
+      } else if (RC->contains(Reg)) {
+        return true;
+      }
+
+      return false;
+    }
+
+    bool IsVSReg(unsigned Reg, MachineRegisterInfo &MRI) {
+      return IsRegInClass(Reg, &PPC::VSRCRegClass, MRI);
+    }
+
+    bool IsVRReg(unsigned Reg, MachineRegisterInfo &MRI) {
+      return IsRegInClass(Reg, &PPC::VRRCRegClass, MRI);
+    }
+
+    bool IsF8Reg(unsigned Reg, MachineRegisterInfo &MRI) {
+      return IsRegInClass(Reg, &PPC::F8RCRegClass, MRI);
+    }
+
+protected:
+    bool processBlock(MachineBasicBlock &MBB) {
+      bool Changed = false;
+
+      MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
+      for (MachineBasicBlock::iterator I = MBB.begin(), IE = MBB.end();
+           I != IE; ++I) {
+        MachineInstr *MI = I;
+        if (!MI->isFullCopy())
+          continue;
+
+        MachineOperand &DstMO = MI->getOperand(0);
+        MachineOperand &SrcMO = MI->getOperand(1);
+
+        if ( IsVSReg(DstMO.getReg(), MRI) &&
+            !IsVSReg(SrcMO.getReg(), MRI)) {
+          // This is a copy *to* a VSX register from a non-VSX register.
+          Changed = true;
+
+          const TargetRegisterClass *SrcRC =
+            IsVRReg(SrcMO.getReg(), MRI) ? &PPC::VSHRCRegClass :
+                                           &PPC::VSLRCRegClass;
+          assert((IsF8Reg(SrcMO.getReg(), MRI) ||
+                  IsVRReg(SrcMO.getReg(), MRI)) &&
+                 "Unknown source for a VSX copy");
+
+          unsigned NewVReg = MRI.createVirtualRegister(SrcRC);
+          BuildMI(MBB, MI, MI->getDebugLoc(),
+                  TII->get(TargetOpcode::SUBREG_TO_REG), NewVReg)
+            .addImm(1) // add 1, not 0, because there is no implicit clearing
+                       // of the high bits.
+            .addOperand(SrcMO)
+            .addImm(IsVRReg(SrcMO.getReg(), MRI) ? PPC::sub_128 :
+                                                   PPC::sub_64);
+
+          // The source of the original copy is now the new virtual register.
+          SrcMO.setReg(NewVReg);
+        } else if (!IsVSReg(DstMO.getReg(), MRI) &&
+                    IsVSReg(SrcMO.getReg(), MRI)) {
+          // This is a copy *from* a VSX register to a non-VSX register.
+          Changed = true;
+
+          const TargetRegisterClass *DstRC =
+            IsVRReg(DstMO.getReg(), MRI) ? &PPC::VSHRCRegClass :
+                                           &PPC::VSLRCRegClass;
+          assert((IsF8Reg(DstMO.getReg(), MRI) ||
+                  IsVRReg(DstMO.getReg(), MRI)) &&
+                 "Unknown destination for a VSX copy");
+
+          // Copy the VSX value into a new VSX register of the correct subclass.
+          unsigned NewVReg = MRI.createVirtualRegister(DstRC);
+          BuildMI(MBB, MI, MI->getDebugLoc(),
+                  TII->get(TargetOpcode::COPY), NewVReg)
+            .addOperand(SrcMO);
+
+          // Transform the original copy into a subregister extraction copy.
+          SrcMO.setReg(NewVReg);
+          SrcMO.setSubReg(IsVRReg(DstMO.getReg(), MRI) ? PPC::sub_128 :
+                                                         PPC::sub_64);
+        }
+      }
+
+      return Changed;
+    }
+
+public:
+    virtual bool runOnMachineFunction(MachineFunction &MF) {
+      TM = static_cast<const PPCTargetMachine *>(&MF.getTarget());
+      TII = TM->getInstrInfo();
+
+      bool Changed = false;
+
+      for (MachineFunction::iterator I = MF.begin(); I != MF.end();) {
+        MachineBasicBlock &B = *I++;
+        if (processBlock(B))
+          Changed = true;
+      }
+
+      return Changed;
+    }
+
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      MachineFunctionPass::getAnalysisUsage(AU);
+    }
+  };
+}
+
+INITIALIZE_PASS(PPCVSXCopy, DEBUG_TYPE,
+                "PowerPC VSX Copy Legalization", false, false)
+
+char PPCVSXCopy::ID = 0;
+FunctionPass*
+llvm::createPPCVSXCopyPass() { return new PPCVSXCopy(); }
+
 #undef DEBUG_TYPE
 #define DEBUG_TYPE "ppc-early-ret"
 STATISTIC(NumBCLR, "Number of early conditional returns");