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

diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index 778ed3b26d2e240e45ba154d5cdab56127c71259..ff8491d2e62ec0d3be688fae75484e4fb017154d 100644 (file)
--- 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 (file)
index 0000000..de0f0b6
--- /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>
+