From e042428b3e1d69205ff422e0c328e28f67b3e465 Mon Sep 17 00:00:00 2001
From: Saleem Abdulrasool <compnerd@compnerd.org>
Date: Thu, 17 Aug 2017 02:42:24 +0000
Subject: [PATCH] ARM: mark CPSR as clobbered for Windows VLAs

When lowering a VLA, we emit a __chstk call.  However, this call can
internally clobber CPSR.  We did not mark this register as an ImpDef,
which could potentially allow a comparison to be hoisted above the call
to `__chkstk`.  In such a case, the CPSR could be clobbered, and the
check invalidated.  When the support was initially added, it seemed that
the call would take care of preventing CPSR from being clobbered, but
this is not the case.  Mark the register as clobbered to fix a possible
state corruption.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@311061 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/ARM/ARMISelLowering.cpp   |  4 ++++
 test/CodeGen/ARM/Windows/vla-cpsr.ll | 13 +++++++++++++
 2 files changed, 17 insertions(+)
 create mode 100644 test/CodeGen/ARM/Windows/vla-cpsr.ll

diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index 778ed3b26d2..ff8491d2e62 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -8790,6 +8790,8 @@ ARMTargetLowering::EmitLowered__chkstk(MachineInstr &MI,
         .addReg(ARM::R4, RegState::Implicit | RegState::Kill)
         .addReg(ARM::R4, RegState::Implicit | RegState::Define)
         .addReg(ARM::R12,
+                RegState::Implicit | RegState::Define | RegState::Dead)
+        .addReg(ARM::CPSR,
                 RegState::Implicit | RegState::Define | RegState::Dead);
     break;
   case CodeModel::Large: {
@@ -8804,6 +8806,8 @@ ARMTargetLowering::EmitLowered__chkstk(MachineInstr &MI,
         .addReg(ARM::R4, RegState::Implicit | RegState::Kill)
         .addReg(ARM::R4, RegState::Implicit | RegState::Define)
         .addReg(ARM::R12,
+                RegState::Implicit | RegState::Define | RegState::Dead)
+        .addReg(ARM::CPSR,
                 RegState::Implicit | RegState::Define | RegState::Dead);
     break;
   }
diff --git a/test/CodeGen/ARM/Windows/vla-cpsr.ll b/test/CodeGen/ARM/Windows/vla-cpsr.ll
new file mode 100644
index 00000000000..de0f0b68a4d
--- /dev/null
+++ b/test/CodeGen/ARM/Windows/vla-cpsr.ll
@@ -0,0 +1,13 @@
+; RUN: llc -mtriple thumbv7-windows-itanium -filetype asm -o /dev/null %s -print-machineinstrs=expand-isel-pseudos 2>&1 | FileCheck %s
+
+declare arm_aapcs_vfpcc void @g(i8*) local_unnamed_addr
+
+define arm_aapcs_vfpcc void @f(i32 %i) local_unnamed_addr {
+entry:
+  %vla = alloca i8, i32 %i, align 1
+  call arm_aapcs_vfpcc void @g(i8* nonnull %vla)
+  ret void
+}
+
+; CHECK: tBL pred:14, pred:%noreg, <es:__chkstk>, %LR<imp-def>, %SP<imp-use>, %R4<imp-use,kill>, %R4<imp-def>, %R12<imp-def,dead>, %CPSR<imp-def,dead>
+
-- 
2.40.0