Re: [PATCH] final: Improve output for -dp and -fverbose-asm

[Segher Boessenkool <segher@kernel.crashing.org>]

On Thu, Nov 30, 2017 at 09:54:26AM -0700, Martin Sebor wrote:
> >It is neither line length nor amt of info that makes the second one
> >way better readable.
> 
> The justification certainly makes it easier to read.  But
> the abbreviations make it harder to interpret.  [c=4 l=4]
> makes no sense to anyone not already familiar with what
> it means.
> 
> There's nothing wrong with using mnemonics as long as they're
> well established and commonly understood.  Absent that, they
> should be explained in some accessible document.
> 
> Not everyone who reads the verbose assembly is familiar with
> GCC internals.  Users read it to help debug problems in their
> code.  They shouldn't have to also study GCC source code to
> understand what the contents mean.

This is the -dp output, I hardly ever use -fverbose-asm, it has been
unreadable for ten years or so.

-fverbose-asm looks like this:
===
.L.yk:
 # 81288.c:4:   unsigned int *un = (f3 != 0) ? &t4 : 0;
        cmpdi 0,4,0      # tmp130, f3
        beq 0,.L2        #
 # 81288.c:6:   *un ^= t4;
        srdi 9,3,32      #, tmp131, t4
        xor 9,9,3        #, tmp132, tmp131, t4
 # 81288.c:7:   if (*un == t4)
        rldicl 9,9,0,32  # tmp133, tmp132
 # 81288.c:7:   if (*un == t4)
        cmpd 7,9,3       # t4, tmp134, tmp133
        beq 7,.L7        #
.L5:
 # 81288.c:11: }
        mr 3,4   #, <retval>
        blr
.L2:
 # 81288.c:6:   *un ^= t4;
        lwz 9,0(4)       # MEM[(unsigned int *)0B], _13
        trap
.L7:
 # 81288.c:8:     f3 = !!t4;
        addic 4,9,-1     # tmp139, tmp133
        subfe 4,4,9      # <retval>, tmp139, tmp133
        b .L5    #
===

If we're okay with outputting that kind of stuff to *users*, then how
bad is [c=8 l=4] for GCC developers?  Heh.


Segher