[llvm] [AArch64][PAC] Lower jump-tables using hardened pseudo. (PR #97666)

[Daniil Kovalev via llvm-commits]

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@@ -10678,6 +10678,21 @@ SDValue AArch64TargetLowering::LowerBR_JT(SDValue Op,
   auto *AFI = DAG.getMachineFunction().getInfo<AArch64FunctionInfo>();
   AFI->setJumpTableEntryInfo(JTI, 4, nullptr);
 
+  // With jump-table-hardening, we only expand the full jump table dispatch
+  // sequence later, to guarantee the integrity of the intermediate values.
+  if (DAG.getMachineFunction().getFunction().hasFnAttribute(
+          "jump-table-hardening") ||
+      Subtarget->getTargetTriple().isArm64e()) {
+    assert(Subtarget->isTargetMachO() &&
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kovdan01 wrote:

Could you please explain what is MachO-specific here? It looks like that at least Linux+ELF could also we supported w/o changing code logic, just by deleting this assertion. ELF tests will require a slight change since assembly syntax and label names are a bit different, so I'm happy to add them by myself later if it's out of scope of the patch.

If there is definitely smth MachO-specific, shouldn't it also be checked in GlobalISel? Alternatively, the check can be moved to the pseudo expansion.

https://github.com/llvm/llvm-project/pull/97666