On 12/8/21 1:08 PM, Jeff Law wrote:
On 12/6/2021 10:32 AM, Martin Sebor wrote:
Attached is subset of the patch in part (4) below: factor out
PHI handling. It applies on top of patch 3/5.
On 12/3/21 5:00 PM, Jeff Law wrote:
On 11/8/2021 7:34 PM, Martin Sebor via Gcc-patches wrote:
The pointer-query code that implements compute_objsize() that's
in turn used by most middle end access warnings now has a few
warts in it and (at least) one bug. With the exception of
the bug the warts aren't behind any user-visible bugs that
I know of but they do cause problems in new code I've been
implementing on top of it. Besides fixing the one bug (just
a typo) the attached patch cleans up these latent issues:
1) It moves the bndrng member from the access_ref class to
access_data. As a FIXME in the code notes, the member never
did belong in the former and only takes up space in the cache.
2) The compute_objsize_r() function is big, unwieldy, and tedious
to step through because of all the if statements that are better
coded as one switch statement. This change factors out more
of its code into smaller handler functions as has been suggested
and done a few times before.
3) (2) exposed a few places where I fail to pass the current
GIMPLE statement down to ranger. This leads to worse quality
range info, including possible false positives and negatives.
I just spotted these problems in code review but I haven't
taken the time to come up with test cases. This change fixes
these oversights as well.
4) The handling of PHI statements is also in one big, hard-to-
follow function. This change moves the handling of each PHI
argument into its own handler which merges it into the previous
argument. This makes the code easier to work with and opens it
to reuse also for MIN_EXPR and MAX_EXPR. (This is primarily
used to print informational notes after warnings.)
5) Finally, the patch factors code to dump each access_ref
cached by the pointer_query cache out of pointer_query::dump
and into access_ref::dump. This helps with debugging.
These changes should have no user-visible effect and other than
a regression test for the typo (PR 103143) come with no tests.
They've been tested on x86_64-linux.
Sigh. You've identified 6 distinct changes above. The 5 you've
enumerated plus a typo fix somewhere. There's no reason why they
need to be a single patch and many reasons why they should be a
series of independent patches. Combining them into a single patch
isn't how we do things and it hides the actual bugfix in here.
Please send a fix for the typo first since that should be able to
trivially go forward. Then a patch for item #1. That should be
trivial to review when it's pulled out from teh rest of the patch.
Beyond that, your choice on ordering, but you need to break this down.
Jeff
gcc-pointer_query-refactor-3.diff
commit 6ac1d37947ad5cf07fe133faaf8414f00e0eed13
Author: Martin Sebor <mse...@redhat.com>
Date: Mon Dec 6 09:23:22 2021 -0700
Introduce access_ref::merge_ref.
gcc/ChangeLog:
* pointer-query.cc (access_ref::merge_ref): Define new
function.
(access_ref::get_ref): Move code into merge_ref and call it.
* pointer-query.h (access_ref::merge_ref): Declare new
function.
OK. But it's probably worth noting that this patch does more than just
factoring out the PHI handling. It also adds the MIN/MAX bits noted in
the original cover letter. That's not inherently as bad now that this
patch isn't intermixed with the other work.
Thank you for the review.
The MIN_MAX change was in the original ChangeLog but I wrote this
one from scratch and neglected to mention it here. Let me add it.
diff --git a/gcc/pointer-query.cc b/gcc/pointer-query.cc
index c75c4da6b60..24fbac84ec4 100644
--- a/gcc/pointer-query.cc
+++ b/gcc/pointer-query.cc
@ -766,7 +818,14 @@ access_ref::get_ref (vec<access_ref> *all_refs,
/* Avoid changing *THIS. */
if (pref && pref != this)
- *pref = phi_ref;
+ {
+ /* Keep the SSA_NAME of the PHI unchanged so that all PHI
arguments
+ can be referred to later if necessary. This is useful even if
+ they all refer to the same object. */
+ tree ref = pref->ref;
+ *pref = phi_ref;
+ pref->ref = ref;
+ }
I don't see any mention of this in the ChangeLog.
This only matters for informational notes, and it's necessary
because the new merge_ref() function might replace the ref
member with that of the "merged" object. It's needed to keep
the existing behavior where we want the informational notes
printed after a warning to point to all the objects that might
be subject to the out of bounds access. This is verified by
the Wstringop-overflow-58.c and -59.c tests.
So I'm fine with the patch itself. I would just ask for a better
ChangeLog. If one was to read the current ChangeLog they could easily
be led to believe this patch was just refactoring, but it brings in
other changes as well.
It wasn't my intention to change any observable behavior with
this change, and I don't think it does.
I was going to update the ChangeLog to mention the MIN/MAX part
above but I just ended up pushing it to the main repository by
mistake.
Martin
