Re: committed [RISC-V]: Harden test scan patterns

[Andrew Pinski <pinskia@gmail.com>]

On Wed, Sep 27, 2023 at 1:14 PM Jeff Law <jeffreyalaw@gmail.com> wrote:
>
>
>
> On 9/27/23 12:22, Joern Rennecke wrote:
> > On Wed, 27 Sept 2023 at 18:22, Jeff Law <jeffreyalaw@gmail.com> wrote:
> >
> >> It would help to describe how these patterns were under specified so
> >> that folks don't continue to make the same mistake as new tests get added.
> >
> > dg-final scan-assembler, scan-assembler-not, and scan-assembler-times
> > use a tcl regular expression (often referred to abbreviated as RE), as
> > described in https://www.tcl.tk/man/tcl8.4/TclCmd/re_syntax.html .
> >
> > If your RE is not specific enough, it can match LTO information that the
> > compiler places into its assembly output when the relevant options are
> > provided, which is common when running tests where the test harness
> > iterates over a number of optimization option combinations.
> > Note that '.' is an atom that can match any character.  If you want to
> > match a dot specifically, you have to escape it with a backslash: '\.' .
> > When you are matching an instruction mnemonic, an effective way to
> > avoid matching in LTO information is to enforce matching of word start
> > (\m) and/or word end (\M) .
> > Note also that the backslash has to be quoted.  If the RE is enclosed in
> > '"' quotes, extra backslashes are needed.  That is not necessary when it
> > is enclosed in curly braces.
> >
> > For example, "ld.w" will be matched in:
> >
> > .ascii  "h\227\022\212ld@w\251jr\254'\320\255vwj\252\026\016\364"
> >
> > If you write {\mld\.w\M} instead, you avoid this problem.
> OK.  So that naturally leads to the question, why aren't others seeing
> this, both in the RISC-V world and more generally.  I'm not aware of any
> case where I've run the testsuite and tripped over this issue, nor am I
> aware of anyone else tripping over it.

I can answer the more generally part. Most other testcases if not all
scan-assembler tries to add spaces that allow not to catch things out
of place. Or even file/directory names.
The documentation at
https://gcc.gnu.org/onlinedocs/gccint/Final-Actions.html (and/or
https://gcc.gnu.org/wiki/HowToPrepareATestcase) definitely could be
expanded to make a mention of these gotchas really.

Thanks,
Andrew

>
> Jeff