Add error messages for emitting LDRA* pseudos without PAuth subtarget feature

Author: kovdan01

llvm/lib/Target/AArch64/AArch64ExpandHardenedPseudos.cpp

@@ -338,6 +338,11 @@ bool AArch64ExpandHardenedPseudos::expandAuthLoad(MachineInstr &MI) {
 
   LLVM_DEBUG(dbgs() << "Expanding: " << MI << "\n");
 
+  // LDRA and LDRApre preudos are emitted in AArch64DAGToDAGISel::tryAuthLoad
+  // and AArch64InstructionSelector::selectAuthLoad with prior checks against
+  // ptrauth subtarget feature
+  assert(STI.hasPAuth());
+
   bool IsPre = MI.getOpcode() == AArch64::LDRApre;
 
   MachineOperand DstOp = MI.getOperand(0);

llvm/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp

@@ -1723,6 +1723,9 @@ bool AArch64DAGToDAGISel::tryAuthLoad(SDNode *N) {
         return false;
   }
 
+  if (!Subtarget->hasPAuth())
+    report_fatal_error("pac instructions require ptrauth target feature");
+
   // We have 2 main isel alternatives:
   // - LDRAA/LDRAB, writeback or indexed.  Zero disc, small offsets, D key.
   // - LDRA/LDRApre.  Pointer needs to be in X16.

llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp

@@ -2856,6 +2856,9 @@ bool AArch64InstructionSelector::select(MachineInstr &I) {
 
   case AArch64::G_LDRA:
   case AArch64::G_LDRApre:
+    // TODO: implement a test case for this error
+    if (!STI.hasPAuth())
+      report_fatal_error("pac instructions require ptrauth target feature");
     return selectAuthLoad(I, MRI);
 
   case TargetOpcode::G_ZEXTLOAD:

llvm/test/CodeGen/AArch64/GlobalISel/ptrauth-lowering-err.ll

@@ -84,3 +84,20 @@ define void @bar(ptr %foo) #0 {
 }
 
 attributes #0 = { "ptrauth-calls" "target-cpu"="generic" }
+
+;--- tryAuthLoad.ll
+
+; RUN: not --crash llc -mtriple aarch64-elf tryAuthLoad.ll 2>&1 | \
+; RUN:   FileCheck tryAuthLoad.ll
+
+; CHECK: LLVM ERROR: pac instructions require ptrauth target feature
+
+define i64 @test(i64* %ptr) {
+  %tmp0 = ptrtoint i64* %ptr to i64
+  %tmp1 = call i64 @llvm.ptrauth.auth(i64 %tmp0, i32 2, i64 0)
+  %tmp2 = inttoptr i64 %tmp1 to i64*
+  %tmp3 = load i64, i64* %tmp2
+  ret i64 %tmp3
+}
+
+declare i64 @llvm.ptrauth.auth(i64, i32, i64)