Adds support for variable sized allocas. For a variable sized alloca,
code is inserted to first check if the current stacklet has enough
space. If so, space is allocated by simply decrementing the stack
pointer. Otherwise a runtime routine (__morestack_allocate_stack_space
in libgcc) is called which allocates the required memory from the
heap.

Patch by Sanjoy Das.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@138818 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.h b/lib/Target/X86/X86ISelLowering.h
index 9a9093c..db59097 100644
--- a/lib/Target/X86/X86ISelLowering.h
+++ b/lib/Target/X86/X86ISelLowering.h
@@ -942,6 +942,10 @@
     MachineBasicBlock *EmitLoweredWinAlloca(MachineInstr *MI,
                                               MachineBasicBlock *BB) const;
 
+    MachineBasicBlock *EmitLoweredSegAlloca(MachineInstr *MI,
+                                            MachineBasicBlock *BB,
+                                            bool Is64Bit) const;
+
     MachineBasicBlock *EmitLoweredTLSCall(MachineInstr *MI,
                                           MachineBasicBlock *BB) const;