[PATCH] fix up compute_objsize (including PR 103143)

Martin Sebor msebor@gmail.com
Tue Nov 9 02:34:13 GMT 2021

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.

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