[llvm] r315781 - [AArch64][RegisterBankInfo] Use the statically computed mappings for COPY

[Quentin Colombet via llvm-commits]

Author: qcolombet
Date: Fri Oct 13 17:43:48 2017
New Revision: 315781

URL: http://llvm.org/viewvc/llvm-project?rev=315781&view=rev
Log:
[AArch64][RegisterBankInfo] Use the statically computed mappings for COPY

We use to resort on the generic implementation to get the mappings for
COPYs. The generic implementation resorts on table lookup and
dynamically allocated objects to get the valid mappings.

Given we already know how to map G_BITCAST and have the static mappings
for them, use that code path for COPY as well. This is much more
efficient.

Improve the compile time of RegBankSelect by up to 20%.

Note: When we eventually generate all the mappings via TableGen, we
wouldn't have to do that dance to shave compile time. The intent of this
change was to make sure that moving to static structure really pays off.

NFC.

Modified:
    llvm/trunk/lib/Target/AArch64/AArch64RegisterBankInfo.cpp

Modified: llvm/trunk/lib/Target/AArch64/AArch64RegisterBankInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64RegisterBankInfo.cpp?rev=315781&r1=315780&r2=315781&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64RegisterBankInfo.cpp (original)
+++ llvm/trunk/lib/Target/AArch64/AArch64RegisterBankInfo.cpp Fri Oct 13 17:43:48 2017
@@ -415,12 +415,10 @@ AArch64RegisterBankInfo::getSameKindOfOp
 const RegisterBankInfo::InstructionMapping &
 AArch64RegisterBankInfo::getInstrMapping(const MachineInstr &MI) const {
   const unsigned Opc = MI.getOpcode();
-  const MachineFunction &MF = *MI.getParent()->getParent();
-  const MachineRegisterInfo &MRI = MF.getRegInfo();
 
   // Try the default logic for non-generic instructions that are either copies
   // or already have some operands assigned to banks.
-  if (!isPreISelGenericOpcode(Opc) ||
+  if ((Opc != TargetOpcode::COPY && !isPreISelGenericOpcode(Opc)) ||
       Opc == TargetOpcode::G_PHI) {
     const RegisterBankInfo::InstructionMapping &Mapping =
         getInstrMappingImpl(MI);
@@ -428,6 +426,11 @@ AArch64RegisterBankInfo::getInstrMapping
       return Mapping;
   }
 
+  const MachineFunction &MF = *MI.getParent()->getParent();
+  const MachineRegisterInfo &MRI = MF.getRegInfo();
+  const TargetSubtargetInfo &STI = MF.getSubtarget();
+  const TargetRegisterInfo &TRI = *STI.getRegisterInfo();
+
   switch (Opc) {
     // G_{F|S|U}REM are not listed because they are not legal.
     // Arithmetic ops.
@@ -451,6 +454,30 @@ AArch64RegisterBankInfo::getInstrMapping
   case TargetOpcode::G_FMUL:
   case TargetOpcode::G_FDIV:
     return getSameKindOfOperandsMapping(MI);
+  case TargetOpcode::COPY: {
+    unsigned DstReg = MI.getOperand(0).getReg();
+    unsigned SrcReg = MI.getOperand(1).getReg();
+    if (TargetRegisterInfo::isPhysicalRegister(DstReg) ||
+        TargetRegisterInfo::isPhysicalRegister(SrcReg)) {
+      const RegisterBank *DstRB = getRegBank(DstReg, MRI, TRI);
+      const RegisterBank *SrcRB = getRegBank(SrcReg, MRI, TRI);
+      if (!DstRB)
+        DstRB = SrcRB;
+      else if (!SrcRB)
+        SrcRB = DstRB;
+      // If both RB are null that means both registers are generic.
+      // We shouldn't be here.
+      assert(DstRB && SrcRB && "Both RegBank were nullptr");
+      unsigned Size = getSizeInBits(DstReg, MRI, TRI);
+      return getInstructionMapping(
+          DefaultMappingID, copyCost(*DstRB, *SrcRB, Size),
+          getCopyMapping(DstRB->getID(), SrcRB->getID(), Size),
+          // We only care about the mapping of the destination.
+          /*NumOperands*/ 1);
+    }
+    // Both registers are generic, use G_BITCAST.
+    LLVM_FALLTHROUGH;
+  }
   case TargetOpcode::G_BITCAST: {
     LLT DstTy = MRI.getType(MI.getOperand(0).getReg());
     LLT SrcTy = MRI.getType(MI.getOperand(1).getReg());
@@ -464,7 +491,8 @@ AArch64RegisterBankInfo::getInstrMapping
     return getInstructionMapping(
         DefaultMappingID, copyCost(DstRB, SrcRB, Size),
         getCopyMapping(DstRB.getID(), SrcRB.getID(), Size),
-        /*NumOperands*/ 2);
+        // We only care about the mapping of the destination for COPY.
+        /*NumOperands*/ Opc == TargetOpcode::G_BITCAST ? 2 : 1);
   }
   default:
     break;