[PATCH] ARM MC: Fix the initial DWARF CFI unwind info at the start of a function

[Keith Walker]

The document http://infocenter.arm.com/help/topic/com.arm.doc.ihi0040b/IHI0040B_aadwarf.pdf provides the ARM specific DWARF information and in Section 3.4 it specifies that

  "The CFA is the value of the stack pointer (r13) at the call site in the previous frame."

This means that the DWARF operation "DW_CFA_def_cfa SP 0" is the correct default for the start of a function.

So this change get's my thumbs up!

Keith

> -----Original Message-----
> From: Rafael Ávila de Espíndola [mailto:rafael.espindola at gmail.com]
> Sent: 23 January 2014 16:04
> To: rafael.espindola at gmail.com; dschuff at google.com;
> jvoung at chromium.org; Keith Walker; mseaborn at chromium.org
> Cc: llvm-commits at cs.uiuc.edu; Amara Emerson
> Subject: Re: [PATCH] ARM MC: Fix the initial DWARF CFI unwind info at
> the start of a function
> 
> 
>   The structure itself it correct. I will let one of the ARM folks give
> the final LGTM to check if that is the correct CFI instruction to use.
> 
> http://llvm-reviews.chandlerc.com/D2597