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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.

llvm-svn: 311061
This commit is contained in:
Saleem Abdulrasool 2017-08-17 02:42:24 +00:00
parent 2f9743d2ea
commit dd8c16b58e
2 changed files with 17 additions and 0 deletions
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4
llvm/lib/Target/ARM/ARMISelLowering.cpp
View File

@ -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;
}

13
llvm/test/CodeGen/ARM/Windows/vla-cpsr.ll Normal file
View File

@ -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>