[stack protector] Fix a potential security bug in stack protector where the

address of the stack guard was being spilled to the stack.

Previously the address of the stack guard would get spilled to the stack if it
was impossible to keep it in a register. This patch introduces a new target
independent node and pseudo instruction which gets expanded post-RA to a
sequence of instructions that load the stack guard value. Register allocator
can now just remat the value when it can't keep it in a register. 

<rdar://problem/12475629>

llvm-svn: 213967

1 files changed, 3 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/Thumb1InstrInfo.h b/llvm/lib/Target/ARM/Thumb1InstrInfo.h
index c5845b75e58..88b1c370195 100644
--- a/llvm/lib/Target/ARM/Thumb1InstrInfo.h
+++ b/llvm/lib/Target/ARM/Thumb1InstrInfo.h
@@ -54,6 +54,9 @@ public:
                             const TargetRegisterClass *RC,
                             const TargetRegisterInfo *TRI) const override;
 
+private:
+  void expandLoadStackGuard(MachineBasicBlock::iterator MI,
+                            Reloc::Model RM) const override;
 };
 }