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

[Matt Arsenault via cfe-commits]

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@@ -5386,6 +5386,130 @@ 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();
+
+  auto createLaneOp = [&](Register &Src0, Register &Src1,
+                          Register &Src2) -> Register {
+    auto LaneOpDst = B.buildIntrinsic(IID, {S32}).addUse(Src0);
+    if (Src2.isValid())
+      return (LaneOpDst.addUse(Src1).addUse(Src2)).getReg(0);
+    if (Src1.isValid())
+      return (LaneOpDst.addUse(Src1)).getReg(0);
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arsenm wrote:

Extra parentheses around this 

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