[AArch64] Emit BTI j on EH landing pads ()

Landing pads reached by the unwinder are entered via 'br', so they must
start with BTI j when -mbranch-protection requests BTI.  Add isEHPad()
to the jump-target test.

Size/perf: +4 B per pad only when BTI is enabled.

Test: new CodeGen/AArch64/bti-ehpad.ll.
Signed-off-by: Shashi Shankar <[email protected]>

Author: shashforge

llvm/lib/Target/AArch64/AArch64BranchTargets.cpp

@@ -100,7 +100,7 @@ bool AArch64BranchTargets::runOnMachineFunction(MachineFunction &MF) {
     // If the block itself is address-taken, it could be indirectly branched
     // to, but not called.
     if (MBB.isMachineBlockAddressTaken() || MBB.isIRBlockAddressTaken() ||
-        JumpTableTargets.count(&MBB))
+        JumpTableTargets.count(&MBB) || MBB.isEHPad())
       CouldJump = true;
 
     if (CouldCall || CouldJump) {

llvm/test/CodeGen/AArch64/bti-ehpad.ll

@@ -0,0 +1,17 @@
+; RUN: llc -mtriple=aarch64-linux-gnu -mbranch-protection=standard %s -o - | FileCheck %s
+
+declare i32 @__gxx_personality_v0(...)
+
+define void @foo() personality ptr @__gxx_personality_v0 {
+entry:
+  invoke void @bar() to label %exit unwind label %lpad
+
+lpad:                                    ; CHECK-LABEL: lpad:
+  landingpad { ptr, i32 } cleanup        ; CHECK:       bti     j
+  resume { ptr null, i32 0 }
+
+exit:
+  ret void
+}
+
+declare void @bar()