[MIPS GlobalISel] Register bank select for G_PHI. Select i64 phi

Select gprb or fprb when def/use register operand of G_PHI is
used/defined by either:
 copy to/from physical register or
 instruction with only one mapping available for that use/def operand.

Integer s64 phi is handled with narrowScalar when mapping is applied,
produced artifacts are combined away. Manually set gprb to all register
operands of instructions created during narrowScalar.

Differential Revision: https://reviews.llvm.org/D64351


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@365494 91177308-0d34-0410-b5e6-96231b3b80d8

Author: Petar Avramovic

lib/CodeGen/GlobalISel/LegalizerHelper.cpp

@@ -708,6 +708,34 @@ LegalizerHelper::LegalizeResult LegalizerHelper::narrowScalar(MachineInstr &MI,
     narrowScalarDst(MI, NarrowTy, 0, TargetOpcode::G_ZEXT);
     Observer.changedInstr(MI);
     return Legalized;
+  case TargetOpcode::G_PHI: {
+    unsigned NumParts = SizeOp0 / NarrowSize;
+    SmallVector<Register, 2> DstRegs;
+    SmallVector<SmallVector<Register, 2>, 2> SrcRegs;
+    DstRegs.resize(NumParts);
+    SrcRegs.resize(MI.getNumOperands() / 2);
+    Observer.changingInstr(MI);
+    for (unsigned i = 1; i < MI.getNumOperands(); i += 2) {
+      MachineBasicBlock &OpMBB = *MI.getOperand(i + 1).getMBB();
+      MIRBuilder.setInsertPt(OpMBB, OpMBB.getFirstTerminator());
+      extractParts(MI.getOperand(i).getReg(), NarrowTy, NumParts,
+                   SrcRegs[i / 2]);
+    }
+    MachineBasicBlock &MBB = *MI.getParent();
+    MIRBuilder.setInsertPt(MBB, MI);
+    for (unsigned i = 0; i < NumParts; ++i) {
+      DstRegs[i] = MRI.createGenericVirtualRegister(NarrowTy);
+      MachineInstrBuilder MIB =
+          MIRBuilder.buildInstr(TargetOpcode::G_PHI).addDef(DstRegs[i]);
+      for (unsigned j = 1; j < MI.getNumOperands(); j += 2)
+        MIB.addUse(SrcRegs[j / 2][i]).add(MI.getOperand(j + 1));
+    }
+    MIRBuilder.setInsertPt(MBB, --MBB.getFirstNonPHI());
+    MIRBuilder.buildMerge(MI.getOperand(0).getReg(), DstRegs);
+    Observer.changedInstr(MI);
+    MI.eraseFromParent();
+    return Legalized;
+  }
   }
 }
 

lib/Target/Mips/MipsLegalizerInfo.cpp

@@ -64,7 +64,7 @@ MipsLegalizerInfo::MipsLegalizerInfo(const MipsSubtarget &ST) {
       .minScalar(0, s32);
 
   getActionDefinitionsBuilder(G_PHI)
-      .legalFor({p0, s32})
+      .legalFor({p0, s32, s64})
       .minScalar(0, s32);
 
   getActionDefinitionsBuilder({G_AND, G_OR, G_XOR})

lib/Target/Mips/MipsRegisterBankInfo.cpp

@@ -195,6 +195,13 @@ MipsRegisterBankInfo::AmbiguousRegDefUseContainer::AmbiguousRegDefUseContainer(
   if (MI->getOpcode() == TargetOpcode::G_STORE)
     addUseDef(MI->getOperand(0).getReg(), MRI);
 
+  if (MI->getOpcode() == TargetOpcode::G_PHI) {
+    addDefUses(MI->getOperand(0).getReg(), MRI);
+
+    for (unsigned i = 1; i < MI->getNumOperands(); i += 2)
+      addUseDef(MI->getOperand(i).getReg(), MRI);
+  }
+
   if (MI->getOpcode() == TargetOpcode::G_SELECT) {
     addDefUses(MI->getOperand(0).getReg(), MRI);
 
@@ -305,9 +312,12 @@ MipsRegisterBankInfo::getInstrMapping(const MachineInstr &MI) const {
   const MachineFunction &MF = *MI.getParent()->getParent();
   const MachineRegisterInfo &MRI = MF.getRegInfo();
 
-  const RegisterBankInfo::InstructionMapping &Mapping = getInstrMappingImpl(MI);
-  if (Mapping.isValid())
-    return Mapping;
+  if (MI.getOpcode() != TargetOpcode::G_PHI) {
+    const RegisterBankInfo::InstructionMapping &Mapping =
+        getInstrMappingImpl(MI);
+    if (Mapping.isValid())
+      return Mapping;
+  }
 
   using namespace TargetOpcode;
 
@@ -384,6 +394,26 @@ MipsRegisterBankInfo::getInstrMapping(const MachineInstr &MI) const {
     }
     break;
   }
+  case G_PHI: {
+    unsigned Size = MRI.getType(MI.getOperand(0).getReg()).getSizeInBits();
+    InstType InstTy = InstType::Integer;
+    if (!MRI.getType(MI.getOperand(0).getReg()).isPointer()) {
+      InstTy = TI.determineInstType(&MI);
+    }
+
+    // PHI is copylike and should have one regbank in mapping for def register.
+    if (InstTy == InstType::Integer && Size == 64) { // fprb
+      OperandsMapping =
+          getOperandsMapping({&Mips::ValueMappings[Mips::DPRIdx]});
+      return getInstructionMapping(CustomMappingID, /*Cost=*/1, OperandsMapping,
+                                   /*NumOperands=*/1);
+    }
+    // Use default handling for PHI, i.e. set reg bank of def operand to match
+    // register banks of use operands.
+    const RegisterBankInfo::InstructionMapping &Mapping =
+        getInstrMappingImpl(MI);
+    return Mapping;
+  }
   case G_SELECT: {
     unsigned Size = MRI.getType(MI.getOperand(0).getReg()).getSizeInBits();
     InstType InstTy = InstType::Integer;
@@ -545,6 +575,7 @@ void MipsRegisterBankInfo::applyMappingImpl(
   switch (MI.getOpcode()) {
   case TargetOpcode::G_LOAD:
   case TargetOpcode::G_STORE:
+  case TargetOpcode::G_PHI:
   case TargetOpcode::G_SELECT: {
     Helper.narrowScalar(MI, 0, LLT::scalar(32));
     // Handle new instructions.