Re: [PATCH] RFC: -fasm-show-source

[Sandra Loosemore <sandra at codesourcery dot com>]

On 08/11/2016 02:34 PM, David Malcolm wrote:
> I sometimes find myself scouring assembler output from the compiler
> and trying to figure out which instructions correspond to which
> lines of source code; I believe this is a common activity for some
> end-users.
>
> The following patch adds a new -fasm-show-source option, which
> emits comments into the generated asm showing the pertinent
> line of source code, whenever it changes.  It uses the same logic
> as debug_hooks->source_line for tracking this (for handling
> line-based breakpoints).
>
> An example can be seen in the invoke.texi part of the patch.  As
> noted there, it's aimed at end-users, rather than gcc developers.
> The example shows a relatively short function; the option is
> likely to be much more useful for longer functions.
>
> I think it would further improve usability if this option were enabled
> by default when the final output is .s (either via -S, or by "-o foo.s").
> Ideas on how to implement that (in the driver) would be welcome - I
> started looking at the spec-handling code, but thought I'd post the
> idea here first, before diving in too deeply.
>
> Successfully bootstrapped&regrtested on x86_64-pc-linux-gnu; adds
> 2 PASS results to gcc.sum.
>
> Thoughts?  OK for trunk as-is?

Why not extend the existing -fverbose-asm to do this?  E.g. 
-fverbose-asm=source, or something like that.  Otherwise you need to 
cross-reference the documentation for the two options and explain how 
they interact (or don't interact, as the case may be).

-Sandra