[llvm] [RISCV][GISEL] Do not initialize GlobalISel objects unless needed (PR #98233)

[Michael Maitland via llvm-commits]

================
@@ -97,29 +97,34 @@ RISCVSubtarget::RISCVSubtarget(const Triple &TT, StringRef CPU,
       RVVVectorBitsMin(RVVVectorBitsMin), RVVVectorBitsMax(RVVVectorBitsMax),
       FrameLowering(
           initializeSubtargetDependencies(TT, CPU, TuneCPU, FS, ABIName)),
-      InstrInfo(*this), RegInfo(getHwMode()), TLInfo(TM, *this) {
-  CallLoweringInfo.reset(new RISCVCallLowering(*getTargetLowering()));
-  Legalizer.reset(new RISCVLegalizerInfo(*this));
-
-  auto *RBI = new RISCVRegisterBankInfo(getHwMode());
-  RegBankInfo.reset(RBI);
-  InstSelector.reset(createRISCVInstructionSelector(
-      *static_cast<const RISCVTargetMachine *>(&TM), *this, *RBI));
-}
+      InstrInfo(*this), RegInfo(getHwMode()), TLInfo(TM, *this) {}
 
 const CallLowering *RISCVSubtarget::getCallLowering() const {
+  if (!CallLoweringInfo)
+    CallLoweringInfo.reset(new RISCVCallLowering(*getTargetLowering()));
   return CallLoweringInfo.get();
 }
 
 InstructionSelector *RISCVSubtarget::getInstructionSelector() const {
+  if (!InstSelector) {
+    if (!RegBankInfo)
----------------
michaelmaitland wrote:

getRegBankInfo returns `const` object.

https://github.com/llvm/llvm-project/pull/98233