[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()) {
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kovdan01 wrote:

Isn't check against arm64e duplicating the check against function attribute? I'm not aware of full arm64e spec, but I suppose that frontend will set "jump-table-hardening" attribute when compiling for arm64e, so there is probably no need for this check here. The same applies to GlobalISel.

Feel free to ignore - I'm OK with such Apple-specific stuff if it's considered essential.

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