On Thu, Jan 13, 2022 at 2:45 AM Qing Zhao <qing.z...@oracle.com> wrote:
>
> Hi, Richard,
>
> This is the updated version for the second patch, which is mainly the change
> for "Enable -Wuninitialized + -ftrivial-auto-var-init for address taken
> variables”.
>
> In this update, I mainly made the following change:
>
> 1. Delete “repl_var”, use the var_def_stmt, i.e, the call to .DEFERRED_INIT
> to record the warning suppressed info.
> 2. Add and change the comments in multiple places to make the change more
> readable.
>
> Now, for the deleted variable, we will get the necessary info to report
> warning from the call to .DEFERRED_INIT.
>
> A. the name string of DECL from the 3rd parameter of the call;
> B. the location of the DECL from the location of the call;
> C. the call can also be used to hold the information on whether the
> warning
> has been issued or not to suppress warning messages when needed;
>
> Please see the detailed description below for the problem and solution of
> this patch.
>
> This patch has been bootstrapped and regressing tested on both X86 and
> aarch64.
>
> Okay for GCC12?
I think the change to split "%qD is used uninitialized" is bad for i8n
though it seems
like none of the strings passed to warn_uninit are currently marked
for localization.
I suppose there's lazy matching with the exact same strings passed to
warning_at around like 641 but after your change those will no longer match up,
at least for the "%qs ..." case constructed. I think a better way
(for i8n) would be
to pass down a flag whether it is "may" or "is" and have the full translatable
strings literally passed to warning_at at the expense of some code duplication.
Actually the extra flag is unnecessary, the OPT_W... we pass is already fully
specifying that.
Instead of doing
+ if (gimple_call_internal_p (var_def_stmt, IFN_DEFERRED_INIT))
+ {
+ /* Ignore the call to .DEFERRED_INIT that define the original
+ var itself as the following case:
+ temp = .DEFERRED_INIT (4, 2, â~@~\alt_reloc");
+ alt_reloc = temp;
+ In order to avoid generating warning for the fake usage
+ at alt_reloc = temp.
...
I thought of many options, none really very appealing so I guess we have to
go with this for now.
So OK with the i8n thing sorted out - please post one hopefully last update
for the patch.
Thanks for your patience,
Richard.
> thanks.
>
> Qing.
>
> ========================
> Enable -Wuninitialized + -ftrivial-auto-var-init for address
> taken variables.
>
> With -ftrivial-auto-var-init, the address taken auto variable is replaced with
> a temporary variable during gimplification, and the original auto variable
> might
> be eliminated by compiler optimization completely. As a result, the current
> uninitialized warning analysis cannot get enough information from the IR,
> therefore the uninitialized warnings for address taken variable cannot be
> issued based on the current implemenation of -ftrival-auto-var-init.
>
> For more info please refer to:
> https://gcc.gnu.org/pipermail/gcc-patches/2021-August/577431.html
>
> In order to improve this situation, we can improve uninitialized analysis
> for address taken auto variables with -ftrivial-auto-var-init as following:
>
> for the following stmt:
>
> _1 = .DEFERRED_INIT (4, 2, &"alt_reloc"[0]);
> if (_1 != 0)
>
> The original variable DECL has been eliminated from the IR, all the necessary
> information that is needed for reporting the warnings for DECL can be acquired
> from the call to .DEFERRED_INIT.
>
> A. the name string of DECL from the 3rd parameter of the call;
> B. the location of the DECL from the location of the call;
> C. the call can also be used to hold the information on whether the
> warning
> has been issued or not to suppress warning messages when needed;
>
> The current testing cases for uninitialized warnings + -ftrivial-auto-var-init
> are adjusted to reflect the fact that we can issue warnings for address taken
> variables.
>
> gcc/ChangeLog:
>
> 2022-01-12 qing zhao <qing.z...@oracle.com>
>
> * tree-ssa-uninit.c (warn_uninit): Handle .DEFERRED_INIT call with an
> anonymous SSA_NAME specially.
> (check_defs): Likewise.
> (warn_uninit_phi_uses): Adjust the message format for warn_uninit.
> (warn_uninitialized_vars): Likewise.
> (warn_uninitialized_phi): Likewise
>
> gcc/testsuite/ChangeLog:
>
> 2022-01-12 qing zhao <qing.z...@oracle.com>
>
> * gcc.dg/auto-init-uninit-16.c (testfunc): Delete xfail to reflect
> the fact that address taken variable can be warned.
> * gcc.dg/auto-init-uninit-34.c (warn_scalar_1): Likewise.
> (warn_scalar_2): Likewise.
> * gcc.dg/auto-init-uninit-37.c (T1): Likewise.
> (T2): Likewise.
> * gcc.dg/auto-init-uninit-B.c (baz): Likewise.
>
> The complete patch is attached:
>
