[clang] [llvm] [AMDGPU][WIP] Extend readlane, writelane and readfirstlane intrinsic lowering for generic types (PR #89217)

[Matt Arsenault via cfe-commits]

================
@@ -5386,6 +5386,153 @@ bool AMDGPULegalizerInfo::legalizeDSAtomicFPIntrinsic(LegalizerHelper &Helper,
   return true;
 }
 
+bool AMDGPULegalizerInfo::legalizeLaneOp(LegalizerHelper &Helper,
+                                         MachineInstr &MI,
+                                         Intrinsic::ID IID) const {
+
+  MachineIRBuilder &B = Helper.MIRBuilder;
+  MachineRegisterInfo &MRI = *B.getMRI();
+
+  Register DstReg = MI.getOperand(0).getReg();
+  Register Src0 = MI.getOperand(2).getReg();
+
+  Register Src1, Src2;
+  if (IID == Intrinsic::amdgcn_readlane || IID == Intrinsic::amdgcn_writelane) {
+    Src1 = MI.getOperand(3).getReg();
+    if (IID == Intrinsic::amdgcn_writelane) {
+      Src2 = MI.getOperand(4).getReg();
+    }
+  }
+
+  LLT Ty = MRI.getType(DstReg);
+  unsigned Size = Ty.getSizeInBits();
+
+  if (Size == 32) {
+    if (Ty.isScalar())
+      // Already legal
+      return true;
+
+    Register Src0Valid = B.buildBitcast(S32, Src0).getReg(0);
+    MachineInstrBuilder LaneOpDst;
+    switch (IID) {
----------------
arsenm wrote:

This isn't quite what I meant; I mean trying to handle these all as they were the same create lane was ugly

https://github.com/llvm/llvm-project/pull/89217