From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from simark.ca (simark.ca [158.69.221.121]) by sourceware.org (Postfix) with ESMTPS id A0663385841A for ; Thu, 2 Mar 2023 16:49:45 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org A0663385841A Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=simark.ca Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=simark.ca Received: from [172.16.0.192] (192-222-180-24.qc.cable.ebox.net [192.222.180.24]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by simark.ca (Postfix) with ESMTPSA id E3C631E110; Thu, 2 Mar 2023 11:49:44 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=simark.ca; s=mail; t=1677775785; bh=Kt/XkKCKMCUxfKLOhFxIo/0Ge6wEleg8Flc+hB5Nzfo=; h=Date:Subject:To:References:From:In-Reply-To:From; b=T6szHbIJjuBxIYK0/ejJ2QaSft5wGf/JJIKxGFRyCTnGmoObAr/E14JO7EYDA4rnf tvOBrBuzvPoyCc4PhMC9bcxgRN7RBRPMrg1F3HGQIiOwZO4V4ydzVFwrDyEvwfHoJE ZdOknnt1hInm4LYo9yCMyasMkiQlvoJWaYowatzo= Message-ID: <5c6af706-bd7d-4c6b-3219-c95e62288aa0@simark.ca> Date: Thu, 2 Mar 2023 11:49:44 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 Subject: Re: [PATCH 1/2] gdb: updates to gdbarch.py algorithm Content-Language: fr To: Andrew Burgess , gdb-patches@sourceware.org References: <871qm7ihpf.fsf@redhat.com> From: Simon Marchi In-Reply-To: <871qm7ihpf.fsf@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-10.9 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,NICE_REPLY_A,SPF_HELO_PASS,SPF_PASS,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On 3/2/23 05:13, Andrew Burgess wrote: > Simon Marchi writes: > >> On 2/28/23 11:51, Andrew Burgess via Gdb-patches wrote: >>> Restructure how gdbarch.py generates the verify_gdbarch function. >>> Previously the postdefault handling was bundled together with the >>> validation. This means that a field can't have both a postdefault, >>> and set its invalid attribute to a string. >>> >>> This doesn't seem reasonable to me, I see no reason why a field can't >>> have both a postdefault (used when the tdep doesn't set the field), >>> and an invalid expression, which can be used to validate the value >>> that a tdep might set. >>> >>> In this commit I restructure the verify_gdbarch generation code to >>> allow the above, there is no change in the actual generated code in >>> this commit, that will come in later commit. >>> >>> I did end up having to remove the "invalid" attribute (where the >>> attribute was set to True) from a number of fields in this commit. >>> This invalid attribute was never having an effect as these components >>> all have a postdefault. Consider; the "postdefault" is applied if the >>> field still has its initial value, while an "invalid" attribute set to >>> True means error if the field still has its default value. But the >>> field never will have its default value, it will always have its >>> postdefault value. >>> --- >>> gdb/gdbarch.py | 31 ++++++++++++++++--------- >>> gdb/gdbarch_components.py | 49 ++++++++++++++------------------------- >>> 2 files changed, 37 insertions(+), 43 deletions(-) >>> >>> diff --git a/gdb/gdbarch.py b/gdb/gdbarch.py >>> index 93b1e8bf84e..7fea41c9572 100755 >>> --- a/gdb/gdbarch.py >>> +++ b/gdb/gdbarch.py >>> @@ -203,35 +203,44 @@ with open("gdbarch.c", "w") as f: >>> file=f, >>> ) >>> for c in filter(not_info, components): >>> - if c.invalid is False: >>> - print(f" /* Skip verify of {c.name}, invalid_p == 0 */", file=f) >>> - elif c.predicate: >>> - print(f" /* Skip verify of {c.name}, has predicate. */", file=f) >>> - elif isinstance(c.invalid, str) and c.postdefault is not None: >>> - print(f" if ({c.invalid})", file=f) >>> - print(f" gdbarch->{c.name} = {c.postdefault};", file=f) >>> - elif c.predefault is not None and c.postdefault is not None: >>> + # An opportunity to write in the 'postdefault' value. >>> + if c.postdefault is not None and c.predefault is not None: >>> print(f" if (gdbarch->{c.name} == {c.predefault})", file=f) >>> print(f" gdbarch->{c.name} = {c.postdefault};", file=f) >>> elif c.postdefault is not None: >>> print(f" if (gdbarch->{c.name} == 0)", file=f) >>> print(f" gdbarch->{c.name} = {c.postdefault};", file=f) >> >> I would find this postdefault snippet easier to read like this, with a >> single "if c.postdefault is not None", and then another condition inside >> to decide what we should compare against: >> >> if c.postdefault is not None: >> if c.predefault is not None: >> print(f" if (gdbarch->{c.name} == {c.predefault})", file=f) >> print(f" gdbarch->{c.name} = {c.postdefault};", file=f) >> else: >> print(f" if (gdbarch->{c.name} == 0)", file=f) >> print(f" gdbarch->{c.name} = {c.postdefault};", file=f) >> >> or even >> >> if c.postdefault is not None: >> predefault = c.predefault or "0" >> print(f" if (gdbarch->{c.name} == {predefault})", file=f) >> print(f" gdbarch->{c.name} = {c.postdefault};", file=f) > > I went with the second approach, I like removing the duplicate print > calls. > >> >>> + >>> + # Now validate the value. >>> + if c.invalid is False: >>> + print(f" /* Skip verify of {c.name}, invalid_p == 0 */", file=f) >>> + elif c.predicate: >>> + print(f" /* Skip verify of {c.name}, has predicate. */", file=f) >>> + elif c.invalid is None: >> >> I think it's confusing for the "invalid" parameter to be able to be >> None, that it's one to many state versus what we need to be able to >> represent. I think we can get by with string, True and False, where >> True means "auto", where the validity check is generated if it makes >> sense to. Having one less state would help simplify things. I hacked >> this locally and it seems to work. I can post this as a cleanup before >> or on top of your patch, as you prefer. >> >> Another cleanup that would help me understand what is going on would be >> to change this long list of if/elif to something that looks more like a >> decision tree. On top of your patch, and on top of my suggestion to get >> rid of the invalid=None state, this is what I made looks like: >> >> predefault = c.predefault or "0" >> >> # Now validate the value. >> if type(c.invalid) is str: >> print(f" if ({c.invalid})", file=f) >> print(f""" log.puts ("\\n\\t{c.name}");""", file=f) >> elif c.invalid: >> if c.predicate: >> print(f" /* Skip verify of {c.name}, has predicate. */", file=f) >> elif c.postdefault: >> # We currently don't print anything, but we could print: >> # print(f" /* Skip verify of {c.name}, has predicate. */", file=f) >> pass >> else: >> print(f" if (gdbarch->{c.name} == {predefault})", file=f) >> print(f""" log.puts ("\\n\\t{c.name}");""", file=f) >> else: >> print(f" /* Skip verify of {c.name}, invalid_p == 0 */", file=f) >> >> That structure is clearer to me. We see clearly the portions handling >> the three states of "invalid" (str, True and False). Inside invalid == >> True (which really means "auto"), we see that we skip generating the >> check when either predicate or postdefault is set, the two situations >> where generating the check doesn't make sense. >> >> Another nice thing about this is that there isn't the "unhandled case >> when generating gdbarch validation" case at the end. Each branch of the >> decision tree has an outcome. >> >> Again, if you agree with this cleanup, we could do it before or after >> your patch, as you wish. > > Yeah, I think what you have above would be a great improvement. I like > that we can (with what you propose) now have an "invalid" string and > also have a predicate, that feels like an improvement. I'm not sure if it was intended, but I don't mind. It would have been useful for my return_value patch (which we will not use in the end). In there, I wanted an "invalid" expression to validate that return_value was not set at the same time as return_value_as_value. But it was also possible to set neither, so I wanted a predicate as well (which would just check != 0). > I've included an update of my patch below. I haven't included the > "invalid" refactor that you describe above as it sounds like you already > have a patch for this work, and it would end up as a separate patch > anyway. I'm fine with it going in after my work of before, whatever > works best. > > Let me know what you think. Thanks, I think this looks good, and we can make further improvements from there. Approved-By: Simon Marchi Simon