Re: [PATCH] Fix debug info with crtl->stack_realign_tried (PR debug/40596)

["H.J. Lu" <hjl dot tools at gmail dot com>]

Hi,

I think the 2nd and 3rd patches should go together.

Xuepeng, can you comment on this? The proposed patches are at

http://gcc.gnu.org/ml/gcc-patches/2009-07/msg00091.html

Thanks.

H.J.
---
On Thu, Jul 2, 2009 at 4:29 AM, Jakub Jelinek<jakub@redhat.com> wrote:
> Hi!
>
> based_loc_descr has:
> ? ? ? ? ?/* If drap register is used to align stack, use frame
> ? ? ? ? ? ? pointer + offset to access stack variables. ?If stack
> ? ? ? ? ? ? is aligned without drap, use stack pointer + offset to
> ? ? ? ? ? ? access stack variables. ?*/
> ? ? ? ? ?if (crtl->stack_realign_tried
> ? ? ? ? ? ? ?&& cfa.reg == HARD_FRAME_POINTER_REGNUM
> ? ? ? ? ? ? ?&& reg == frame_pointer_rtx)
> ? ? ? ? ? ?{
> ? ? ? ? ? ? ?int base_reg
> ? ? ? ? ? ? ? ?= DWARF_FRAME_REGNUM (cfa.indirect
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?? HARD_FRAME_POINTER_REGNUM
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?: STACK_POINTER_REGNUM);
> ? ? ? ? ? ? ?return new_reg_loc_descr (base_reg, offset);
> ? ? ? ? ? ?}
>
> ? ? ? ? ?offset += frame_pointer_fb_offset;
> ? ? ? ? ?return new_loc_descr (DW_OP_fbreg, offset, 0);
> which got broken by epilogue unwinding support; before epilogue unwinding
> was added cfa variable at the point where based_loc_descr is called (after
> assembly for the function has been emitted) contained the CFA state after
> prologue, but that is no longer true if epilogue has unwind info and isn't
> followed by other code. ?Attached are two different fixes.
> The first patch changes dwarf2out_{begin,end}_epilogue, so that even when
> epilogue has unwind info, but isn't followed by anything else, cfa variable
> is restored to the state in the middle of the function.
>
> I've bootstrapped/regtested this patch on x86_64-linux and i686-linux with
> the second patch on top of it and the assert never triggered, so I'm
> assuming if crtl->stack_realign_tried is true, cfa.reg in the middle of
> function is always HARD_FRAME_POINTER_REGNUM (if stack is dynamically
> realigned, I think frame pointer is always forced) and cfa.indirect is true
> iff fde->drap_reg is not invalid.
>
> If so, then we could as well use the third patch instead of the first, never
> rely on cfa content after function has been emitted into assembly.
>
> Both the first and third patch fix the testcase in the PR:
> ? ? ? ?.uleb128 0xd ? ?# (DIE (0xef) DW_TAG_variable)
> ? ? ? ?.ascii "a3\0" ? # DW_AT_name
> ? ? ? ?.byte ? 0x1 ? ? # DW_AT_decl_file (pr40596.c)
> ? ? ? ?.byte ? 0x18 ? ?# DW_AT_decl_line
> ? ? ? ?.long ? 0x46 ? ?# DW_AT_type
> ? ? ? ?.byte ? 0x2 ? ? # DW_AT_location
> - ? ? ? .byte ? 0x91 ? ?# DW_OP_fbreg
> - ? ? ? .sleb128 20
> + ? ? ? .byte ? 0x74 ? ?# DW_OP_breg4
> + ? ? ? .sleb128 28
>
> ? ? ? ?Jakub
>



-- 
H.J.