[llvm] [AArch64][PAC] Lower direct authenticated calls to ptrauth constants. (PR #97664)

[Daniil Kovalev via llvm-commits]

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@@ -2649,17 +2649,24 @@ bool IRTranslator::translateCallBase(const CallBase &CB,
   }
 
   std::optional<CallLowering::PtrAuthInfo> PAI;
-  if (CB.countOperandBundlesOfType(LLVMContext::OB_ptrauth)) {
+  if (auto Bundle = CB.getOperandBundle(LLVMContext::OB_ptrauth)) {
     // Functions should never be ptrauth-called directly.
     assert(!CB.getCalledFunction() && "invalid direct ptrauth call");
 
-    auto PAB = CB.getOperandBundle("ptrauth");
-    const Value *Key = PAB->Inputs[0];
-    const Value *Discriminator = PAB->Inputs[1];
-
-    Register DiscReg = getOrCreateVReg(*Discriminator);
-    PAI = CallLowering::PtrAuthInfo{cast<ConstantInt>(Key)->getZExtValue(),
-                                    DiscReg};
+    const Value *Key = Bundle->Inputs[0];
+    const Value *Discriminator = Bundle->Inputs[1];
+
+    // Look through ptrauth constants to try to eliminate the matching bundle
+    // and turn this into a direct call with no ptrauth.
+    // CallLowering will use the raw pointer if it doesn't find the PAI.
+    auto *CalleeCPA = dyn_cast<ConstantPtrAuth>(CB.getCalledOperand());
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kovdan01 wrote:

```suggestion
    const auto *CalleeCPA = dyn_cast<ConstantPtrAuth>(CB.getCalledOperand());
```

https://github.com/llvm/llvm-project/pull/97664