NuPlusFrameLowering class

The NuPlusFrameLowering class must handle all the operations concerning the stack frame. It implements the TargetFrameLowering interface. In nu+ the stack grows incrementing the address (i.e. the stack grows down) and it is 64-byte aligned. The NuPlusFrameLowering implements the following functions:

• emitPrologue and emitEpilogue, which insert prolog and epilog code into the function.
• eliminateCallFramePseudoInstr, responsible for eliminating call frame setup and destroy pseudo instructions, replacing them with concrete instructions.
• hasReservedCallFrame, returns true if the prologue inserter should reserve space for outgoing arguments.
• hasFP, returns true if the specified function should have a dedicated frame pointer register. This is true if the function has variable sized allocas or if frame pointer elimination is disabled.
• determineCalleeSaves, determines which of the registers reported by TargetRegisterInfo::getCalleeSavedRegs() should actually get saved.