[clang] [llvm] [AArch64][PAC] Sign block addresses used in indirectbr. (PR #97647)

[Ahmed Bougacha via cfe-commits]

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@@ -10685,6 +10689,26 @@ SDValue AArch64TargetLowering::LowerBR_JT(SDValue Op,
   return DAG.getNode(ISD::BRIND, DL, MVT::Other, JTInfo, SDValue(Dest, 0));
 }
 
+SDValue AArch64TargetLowering::LowerBRIND(SDValue Op, SelectionDAG &DAG) const {
+  MachineFunction &MF = DAG.getMachineFunction();
+  std::optional<uint16_t> BADisc =
+      Subtarget->getPtrAuthBlockAddressDiscriminator(MF.getFunction());
+  if (!BADisc)
+    return SDValue();
+
+  SDLoc DL(Op);
+  SDValue Chain = Op.getOperand(0);
+  SDValue Dest = Op.getOperand(1);
+
+  SDValue Disc = DAG.getTargetConstant(*BADisc, DL, MVT::i64);
+  SDValue Key = DAG.getTargetConstant(AArch64PACKey::IA, DL, MVT::i32);
+  SDValue AddrDisc = DAG.getRegister(AArch64::XZR, MVT::i64);
+
+  SDNode *BrA = DAG.getMachineNode(AArch64::BRA, DL, MVT::Other,
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ahmedbougacha wrote:

Interesting, that explains it.  I'd rather have the BR_JT survive as a BR_JT (or really, an AArch64 BR_JT that's analogous to ISD::BRIND, so that we can still do what we do on JumpTableDests), but that's a more serious change for the whole backend; let's do it separately.  For now checking the target seems iffy but probably workable

https://github.com/llvm/llvm-project/pull/97647