[llvm][AArch64] Preserve regmask when expanding the BLR_BTI pseudo instruction (#73927)

Fixes #73787

Not doing so lead to us making use of a register after the call, which
has been clobbered by the call.

Added an MIR test that runs only the pseudo expansion pass.

Author: DavidSpickett

llvm/lib/Target/AArch64/AArch64ExpandPseudoInsts.cpp

@@ -837,6 +837,7 @@ bool AArch64ExpandPseudo::expandCALL_BTI(MachineBasicBlock &MBB,
       BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(Opc)).getInstr();
   Call->addOperand(CallTarget);
   Call->setCFIType(*MBB.getParent(), MI.getCFIType());
+  Call->copyImplicitOps(*MBB.getParent(), MI);
 
   MachineInstr *BTI =
       BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(AArch64::HINT))

llvm/test/CodeGen/AArch64/blr-bti-preserves-regmask.mir

@@ -0,0 +1,23 @@
+# RUN: llc -mtriple=aarch64-none-linux-gnu -run-pass=aarch64-expand-pseudo -o - %s | FileCheck %s
+
+# When expanding a BLR_BTI, we should keep the regmask that was attached to it.
+# Otherwise we could end up using a register after the BL which was clobbered by
+# the function that was called.
+# CHECK:    BUNDLE implicit-def $lr, implicit-def $w30, implicit-def $sp, implicit-def $wsp, implicit $sp {
+# CHECK:      BL @_setjmp, csr_aarch64_aapcs, implicit-def $lr, implicit $sp, implicit-def dead $lr, implicit $sp, implicit-def $sp
+# CHECK:      HINT 36
+# CHECK:    }
+
+--- |
+  define void @a() {
+    ret void
+  }
+
+  declare void @_setjmp(...)
+...
+---
+name: a
+body: |
+  bb.0:
+    BLR_BTI @_setjmp, csr_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit-def $sp
+...

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

@@ -49,7 +49,7 @@ define void @f2(ptr noundef %x) !kcfi_type !2 {
 
 ; KCFI:       BUNDLE{{.*}} {
 ; KCFI-NEXT:    KCFI_CHECK $x0, 12345678, implicit-def $x9, implicit-def $x16, implicit-def $x17, implicit-def $nzcv
-; KCFI-NEXT:    BLR killed $x0, implicit-def $lr, implicit $sp
+; KCFI-NEXT:    BLR killed $x0, csr_aarch64_aapcs, implicit-def $lr, implicit $sp, implicit-def dead $lr, implicit $sp, implicit-def $sp
 ; KCFI-NEXT:    HINT 36
 ; KCFI-NEXT:  }