From 872e6a81fc41f01236ee5c5b74a5d33d92fac2a9 Mon Sep 17 00:00:00 2001
From: Tim Northover <tnorthover@apple.com>
Date: Tue, 12 Nov 2013 21:32:41 +0000
Subject: [PATCH] ARM: diagnose invalid system LDM/STM

The system LDM and STM instructions can't usually writeback to the base
register. The one exception is when an LDM is actually an exception-return
(i.e. contains PC in the register list).

(There's already a test that "ldm sp!, {r0-r3, pc}^" works, which is why there
is no positive test).

rdar://problem/15223374

llvm-svn: 194512
---
 lib/Target/ARM/AsmParser/ARMAsmParser.cpp | 16 ++++++++++++++++
 test/MC/ARM/diagnostics.s                 |  5 +++++
 2 files changed, 21 insertions(+)

diff --git a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index 727bd26369c..e3f9e0dc609 100644
--- a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -5481,6 +5481,22 @@ validateInstruction(MCInst &Inst,
                    "writeback register not allowed in register list");
     break;
   }
+  case ARM::sysLDMIA_UPD:
+  case ARM::sysLDMDA_UPD:
+  case ARM::sysLDMDB_UPD:
+  case ARM::sysLDMIB_UPD:
+    if (!listContainsReg(Inst, 3, ARM::PC))
+      return Error(Operands[4]->getStartLoc(),
+                   "writeback register only allowed on system LDM "
+                   "if PC in register-list");
+    break;
+  case ARM::sysSTMIA_UPD:
+  case ARM::sysSTMDA_UPD:
+  case ARM::sysSTMDB_UPD:
+  case ARM::sysSTMIB_UPD:
+    return Error(Operands[2]->getStartLoc(),
+                 "system STM cannot have writeback register");
+    break;
   case ARM::tMUL: {
     // The second source operand must be the same register as the destination
     // operand.
diff --git a/test/MC/ARM/diagnostics.s b/test/MC/ARM/diagnostics.s
index 11c8306b1d7..3c26f6d645c 100644
--- a/test/MC/ARM/diagnostics.s
+++ b/test/MC/ARM/diagnostics.s
@@ -460,3 +460,8 @@
 @ CHECK-ERRORS: error: instruction requires: FPARMv8
 @ CHECK-ERRORS: error: instruction requires: FPARMv8
 @ CHECK-ERRORS: error: instruction requires: FPARMv8
+
+        stm sp!, {r0, pc}^
+        ldm sp!, {r0}^
+@ CHECK-ERRORS: error: system STM cannot have writeback register
+@ CHECK-ERRORS: error: writeback register only allowed on system LDM if PC in register-list