[llvm] [InstCombine] Combine ptrauth intrin. callee into same-key bundle. (PR #94707)

[Daniil Kovalev via llvm-commits]

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@@ -3665,6 +3665,78 @@ static IntrinsicInst *findInitTrampoline(Value *Callee) {
   return nullptr;
 }
 
+Instruction *InstCombinerImpl::foldPtrAuthIntrinsicCallee(CallBase &Call) {
+  Value *Callee = Call.getCalledOperand();
+  auto *IPC = dyn_cast<IntToPtrInst>(Callee);
+  if (!IPC || !IPC->isNoopCast(DL))
+    return nullptr;
+
+  IntrinsicInst *II = dyn_cast<IntrinsicInst>(IPC->getOperand(0));
+  if (!II)
+    return nullptr;
+
+  // Isolate the ptrauth bundle from the others.
+  std::optional<OperandBundleUse> PtrAuthBundleOrNone;
+  SmallVector<OperandBundleDef, 2> NewBundles;
+  for (unsigned BI = 0, BE = Call.getNumOperandBundles(); BI != BE; ++BI) {
+    OperandBundleUse Bundle = Call.getOperandBundleAt(BI);
+    if (Bundle.getTagID() == LLVMContext::OB_ptrauth)
+      PtrAuthBundleOrNone = Bundle;
+    else
+      NewBundles.emplace_back(Bundle);
+  }
+
+  Value *NewCallee = nullptr;
+  switch (II->getIntrinsicID()) {
+  default:
+    return nullptr;
+
+  // call(ptrauth.resign(p)), ["ptrauth"()] ->  call p, ["ptrauth"()]
+  // assuming the call bundle and the sign operands match.
+  case Intrinsic::ptrauth_resign: {
+    if (!PtrAuthBundleOrNone ||
+        II->getOperand(3) != PtrAuthBundleOrNone->Inputs[0] ||
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kovdan01 wrote:

Feel free to ignore: it's probably worth adding comments which say that operand N stands for X (e.g. operand 3 of intrinsic is a key to be resigned with). You already split the if into multiple parts instead of just using a giant condition in one if, so it looks like that there is not problem to split it even further and use multiple if statements with simple conditions and corresponding comments.

https://github.com/llvm/llvm-project/pull/94707