[PowerPC] Always use mfocrf if available

When accessing just a single CR register, it is always preferable to
use mfocrf instead of mfcr, if the former is available on the CPU.

Current code makes that distinction in many, but not all places
where a single CR register value is retrieved.  One missing
location is PPCRegisterInfo::lowerCRSpilling.

To fix this and make this simpler in the future, this patch changes
the bulk of the back-end to always assume mfocrf is available and
simply generate it when needed.

On machines that actually do not support mfocrf, the instruction
is replaced by mfcr at the very end, in EmitInstruction.

This has the additional benefit that we no longer need the
MFCRpseud hack, since before EmitInstruction we always have
a MFOCRF instruction pattern, which already models data flow
as required.

The patch also adds the MFOCRF8 version of the instruction,
which was missing so far.

Except for the PPCRegisterInfo::lowerCRSpilling case, no change
in generated code intended.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185556 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/PowerPC/MCTargetDesc/PPCMCCodeEmitter.cpp

@@ -228,9 +228,8 @@ unsigned PPCMCCodeEmitter::
 get_crbitm_encoding(const MCInst &MI, unsigned OpNo,
                     SmallVectorImpl<MCFixup> &Fixups) const {
   const MCOperand &MO = MI.getOperand(OpNo);
-  assert((MI.getOpcode() == PPC::MTCRF || 
+  assert((MI.getOpcode() == PPC::MTCRF || MI.getOpcode() == PPC::MTCRF8 ||
-          MI.getOpcode() == PPC::MFOCRF ||
+          MI.getOpcode() == PPC::MFOCRF || MI.getOpcode() == PPC::MFOCRF8) &&
-          MI.getOpcode() == PPC::MTCRF8) &&
          (MO.getReg() >= PPC::CR0 && MO.getReg() <= PPC::CR7));
   return 0x80 >> CTX.getRegisterInfo()->getEncodingValue(MO.getReg());
 }
@@ -242,7 +241,8 @@ getMachineOpValue(const MCInst &MI, const MCOperand &MO,
   if (MO.isReg()) {
     // MTCRF/MFOCRF should go through get_crbitm_encoding for the CR operand.
     // The GPR operand should come through here though.
-    assert((MI.getOpcode() != PPC::MTCRF && MI.getOpcode() != PPC::MFOCRF) ||
+    assert((MI.getOpcode() != PPC::MTCRF && MI.getOpcode() != PPC::MTCRF8 &&
+            MI.getOpcode() != PPC::MFOCRF && MI.getOpcode() != PPC::MFOCRF8) ||
            MO.getReg() < PPC::CR0 || MO.getReg() > PPC::CR7);
     return CTX.getRegisterInfo()->getEncodingValue(MO.getReg());
   }

lib/Target/PowerPC/PPCAsmPrinter.cpp

@@ -662,15 +662,20 @@ void PPCAsmPrinter::EmitInstruction(const MachineInstr *MI) {
                                 .addExpr(SymDtprel));
     return;
   }
-  case PPC::MFCRpseud:
+  case PPC::MFOCRF:
-  case PPC::MFCR8pseud:
+  case PPC::MFOCRF8:
-    // Transform: %R3 = MFCRpseud %CR7
+    if (!Subtarget.hasMFOCRF()) {
-    // Into:      %R3 = MFCR      ;; cr7
+      // Transform: %R3 = MFOCRF %CR7
-    OutStreamer.AddComment(PPCInstPrinter::
+      // Into:      %R3 = MFCR   ;; cr7
-                           getRegisterName(MI->getOperand(1).getReg()));
+      unsigned NewOpcode =
-    OutStreamer.EmitInstruction(MCInstBuilder(Subtarget.isPPC64() ? PPC::MFCR8 : PPC::MFCR)
+        MI->getOpcode() == PPC::MFOCRF ? PPC::MFCR : PPC::MFCR8;
-      .addReg(MI->getOperand(0).getReg()));
+      OutStreamer.AddComment(PPCInstPrinter::
-    return;
+                             getRegisterName(MI->getOperand(1).getReg()));
+      OutStreamer.EmitInstruction(MCInstBuilder(NewOpcode)
+                                  .addReg(MI->getOperand(0).getReg()));
+      return;
+    }
+    break;
   case PPC::SYNC:
     // In Book E sync is called msync, handle this special case here...
     if (Subtarget.isBookE()) {

lib/Target/PowerPC/PPCCodeEmitter.cpp

@@ -143,7 +143,7 @@ unsigned PPCCodeEmitter::get_crbitm_encoding(const MachineInstr &MI,
                                              unsigned OpNo) const {
   const MachineOperand &MO = MI.getOperand(OpNo);
   assert((MI.getOpcode() == PPC::MTCRF || MI.getOpcode() == PPC::MTCRF8 ||
-            MI.getOpcode() == PPC::MFOCRF) &&
+          MI.getOpcode() == PPC::MFOCRF || MI.getOpcode() == PPC::MFOCRF8) &&
          (MO.getReg() >= PPC::CR0 && MO.getReg() <= PPC::CR7));
   return 0x80 >> TM.getRegisterInfo()->getEncodingValue(MO.getReg());
 }
@@ -277,7 +277,7 @@ unsigned PPCCodeEmitter::getMachineOpValue(const MachineInstr &MI,
     // MTCRF/MFOCRF should go through get_crbitm_encoding for the CR operand.
     // The GPR operand should come through here though.
     assert((MI.getOpcode() != PPC::MTCRF && MI.getOpcode() != PPC::MTCRF8 &&
-             MI.getOpcode() != PPC::MFOCRF) ||
+            MI.getOpcode() != PPC::MFOCRF && MI.getOpcode() != PPC::MFOCRF8) ||
            MO.getReg() < PPC::CR0 || MO.getReg() > PPC::CR7);
     return TM.getRegisterInfo()->getEncodingValue(MO.getReg());
   }

lib/Target/PowerPC/PPCISelDAGToDAG.cpp

@@ -854,12 +854,8 @@ SDNode *PPCDAGToDAGISel::SelectSETCC(SDNode *N) {
   CCReg = CurDAG->getCopyToReg(CurDAG->getEntryNode(), dl, CR7Reg, CCReg,
                                InFlag).getValue(1);
 
-  if (PPCSubTarget.hasMFOCRF())
+  IntCR = SDValue(CurDAG->getMachineNode(PPC::MFOCRF, dl, MVT::i32, CR7Reg,
-    IntCR = SDValue(CurDAG->getMachineNode(PPC::MFOCRF, dl, MVT::i32, CR7Reg,
+                                         CCReg), 0);
-                                           CCReg), 0);
-  else
-    IntCR = SDValue(CurDAG->getMachineNode(PPC::MFCRpseud, dl, MVT::i32,
-                                           CR7Reg, CCReg), 0);
 
   SDValue Ops[] = { IntCR, getI32Imm((32-(3-Idx)) & 31),
                       getI32Imm(31), getI32Imm(31) };
@@ -974,15 +970,10 @@ SDNode *PPCDAGToDAGISel::Select(SDNode *N) {
                                   getSmallIPtrImm(0));
   }
 
-  case PPCISD::MFCR: {
+  case PPCISD::MFOCRF: {
     SDValue InFlag = N->getOperand(1);
-    // Use MFOCRF if supported.
+    return CurDAG->getMachineNode(PPC::MFOCRF, dl, MVT::i32,
-    if (PPCSubTarget.hasMFOCRF())
+                                  N->getOperand(0), InFlag);
-      return CurDAG->getMachineNode(PPC::MFOCRF, dl, MVT::i32,
-                                    N->getOperand(0), InFlag);
-    else
-      return CurDAG->getMachineNode(PPC::MFCRpseud, dl, MVT::i32,
-                                    N->getOperand(0), InFlag);
   }
 
   case ISD::SDIV: {

lib/Target/PowerPC/PPCISelLowering.cpp

@@ -626,7 +626,7 @@ const char *PPCTargetLowering::getTargetNodeName(unsigned Opcode) const {
   case PPCISD::RET_FLAG:        return "PPCISD::RET_FLAG";
   case PPCISD::EH_SJLJ_SETJMP:  return "PPCISD::EH_SJLJ_SETJMP";
   case PPCISD::EH_SJLJ_LONGJMP: return "PPCISD::EH_SJLJ_LONGJMP";
-  case PPCISD::MFCR:            return "PPCISD::MFCR";
+  case PPCISD::MFOCRF:          return "PPCISD::MFOCRF";
   case PPCISD::VCMP:            return "PPCISD::VCMP";
   case PPCISD::VCMPo:           return "PPCISD::VCMPo";
   case PPCISD::LBRX:            return "PPCISD::LBRX";
@@ -5539,7 +5539,7 @@ SDValue PPCTargetLowering::LowerINTRINSIC_WO_CHAIN(SDValue Op,
 
   // Now that we have the comparison, emit a copy from the CR to a GPR.
   // This is flagged to the above dot comparison.
-  SDValue Flags = DAG.getNode(PPCISD::MFCR, dl, MVT::i32,
+  SDValue Flags = DAG.getNode(PPCISD::MFOCRF, dl, MVT::i32,
                                 DAG.getRegister(PPC::CR6, MVT::i32),
                                 CompNode.getValue(1));
 
@@ -7293,16 +7293,16 @@ SDValue PPCTargetLowering::PerformDAGCombine(SDNode *N,
         }
       }
 
-      // If the user is a MFCR instruction, we know this is safe.  Otherwise we
+      // If the user is a MFOCRF instruction, we know this is safe.
-      // give up for right now.
+      // Otherwise we give up for right now.
-      if (FlagUser->getOpcode() == PPCISD::MFCR)
+      if (FlagUser->getOpcode() == PPCISD::MFOCRF)
         return SDValue(VCMPoNode, 0);
     }
     break;
   }
   case ISD::BR_CC: {
     // If this is a branch on an altivec predicate comparison, lower this so
-    // that we don't have to do a MFCR: instead, branch directly on CR6.  This
+    // that we don't have to do a MFOCRF: instead, branch directly on CR6.  This
     // lowering is done pre-legalize, because the legalizer lowers the predicate
     // compare down to code that is difficult to reassemble.
     ISD::CondCode CC = cast<CondCodeSDNode>(N->getOperand(1))->get();

lib/Target/PowerPC/PPCISelLowering.h

@@ -116,11 +116,10 @@ namespace llvm {
       /// Return with a flag operand, matched by 'blr'
       RET_FLAG,
 
-      /// R32 = MFCR(CRREG, INFLAG) - Represents the MFCRpseud/MFOCRF
+      /// R32 = MFOCRF(CRREG, INFLAG) - Represents the MFOCRF instruction.
-      /// instructions.  This copies the bits corresponding to the specified
+      /// This copies the bits corresponding to the specified CRREG into the
-      /// CRREG into the resultant GPR.  Bits corresponding to other CR regs
+      /// resultant GPR.  Bits corresponding to other CR regs are undefined.
-      /// are undefined.
+      MFOCRF,
-      MFCR,
 
       // EH_SJLJ_SETJMP - SjLj exception handling setjmp.
       EH_SJLJ_SETJMP,

lib/Target/PowerPC/PPCInstr64Bit.td

@@ -261,16 +261,14 @@ def MTCRF8 : XFXForm_5<31, 144, (outs crbitm:$FXM), (ins g8rc:$rS),
                       "mtcrf $FXM, $rS", BrMCRX>,
             PPC970_MicroCode, PPC970_Unit_CRU;
 
-let isCodeGenOnly = 1 in
+def MFOCRF8: XFXForm_5a<31, 19, (outs g8rc:$rT), (ins crbitm:$FXM),
-def MFCR8pseud: XFXForm_3<31, 19, (outs g8rc:$rT), (ins crbitm:$FXM),
+                        "mfocrf $rT, $FXM", SprMFCR>,
-                       "#MFCR8pseud", SprMFCR>,
+             PPC970_DGroup_First, PPC970_Unit_CRU;
-            PPC970_MicroCode, PPC970_Unit_CRU;
-} // neverHasSideEffects = 1
 
-let neverHasSideEffects = 1 in
 def MFCR8 : XFXForm_3<31, 19, (outs g8rc:$rT), (ins),
                      "mfcr $rT", SprMFCR>,
                      PPC970_MicroCode, PPC970_Unit_CRU;
+} // neverHasSideEffects = 1
 
 let hasSideEffects = 1, isBarrier = 1, usesCustomInserter = 1 in {
   def EH_SjLj_SetJmp64  : Pseudo<(outs gprc:$dst), (ins memr:$buf),

lib/Target/PowerPC/PPCInstrInfo.td

@@ -1902,30 +1902,14 @@ def MTCRF : XFXForm_5<31, 144, (outs crbitm:$FXM), (ins gprc:$rS),
                       "mtcrf $FXM, $rS", BrMCRX>,
             PPC970_MicroCode, PPC970_Unit_CRU;
 
-// This is a pseudo for MFCR, which implicitly uses all 8 of its subregisters;
-// declaring that here gives the local register allocator problems with this:
-//  vreg = MCRF  CR0
-//  MFCR  <kill of whatever preg got assigned to vreg>
-// while not declaring it breaks DeadMachineInstructionElimination.
-// As it turns out, in all cases where we currently use this,
-// we're only interested in one subregister of it.  Represent this in the
-// instruction to keep the register allocator from becoming confused.
-//
-// FIXME: Make this a real Pseudo instruction when the JIT switches to MC.
-let isCodeGenOnly = 1 in
-def MFCRpseud: XFXForm_3<31, 19, (outs gprc:$rT), (ins crbitm:$FXM),
-                       "#MFCRpseud", SprMFCR>,
-            PPC970_MicroCode, PPC970_Unit_CRU;
-
 def MFOCRF: XFXForm_5a<31, 19, (outs gprc:$rT), (ins crbitm:$FXM),
                        "mfocrf $rT, $FXM", SprMFCR>,
             PPC970_DGroup_First, PPC970_Unit_CRU;
-} // neverHasSideEffects = 1
 
-let neverHasSideEffects = 1 in
 def MFCR : XFXForm_3<31, 19, (outs gprc:$rT), (ins),
                      "mfcr $rT", SprMFCR>,
                      PPC970_MicroCode, PPC970_Unit_CRU;
+} // neverHasSideEffects = 1
 
 // Pseudo instruction to perform FADD in round-to-zero mode.
 let usesCustomInserter = 1, Uses = [RM] in {

lib/Target/PowerPC/PPCRegisterInfo.cpp

@@ -342,8 +342,8 @@ void PPCRegisterInfo::lowerCRSpilling(MachineBasicBlock::iterator II,
   unsigned SrcReg = MI.getOperand(0).getReg();
 
   // We need to store the CR in the low 4-bits of the saved value. First, issue
-  // an MFCRpsued to save all of the CRBits and, if needed, kill the SrcReg.
+  // an MFOCRF to save all of the CRBits and, if needed, kill the SrcReg.
-  BuildMI(MBB, II, dl, TII.get(LP64 ? PPC::MFCR8pseud : PPC::MFCRpseud), Reg)
+  BuildMI(MBB, II, dl, TII.get(LP64 ? PPC::MFOCRF8 : PPC::MFOCRF), Reg)
           .addReg(SrcReg, getKillRegState(MI.getOperand(0).isKill()));
     
   // If the saved register wasn't CR0, shift the bits left so that they are in