[Bug tree-optimization/60165] "may be used uninitialized" warning with -O3 but not with -O2

["glisse at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60165

--- Comment #13 from Marc Glisse <glisse at gcc dot gnu.org> ---
(In reply to Manuel López-Ibáñez from comment #10)
> Now, I agree that ideally, GCC should warn for your last testcase. But I
> guess in that case inlining either doesn't happen or it happens too late, so
> GCC only sees the first case.

Actually it is the reverse, inlining happens earlier in this new testcase (the
first example was recursive, which makes the inliner more conservative).

> The analysis that GCC performs are predicated
> on the transformations leading to better code, otherwise they are not
> performed. A tool for static analysis will surely inline as much as it
> could, not matter if the code is slower or larger, but this is not how GCC
> works because GCC is not a tool for static analysis.

Maybe we could have a wiki page explaining what options to tweak (inlining
parameters, etc) for a compilation where you are only interested in warnings?
(I had vaguely mentioned creating -Ow at some point, but that didn't seem such
a good idea)
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From: "bernd.edlinger at hotmail dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug ada/60174] New: ICE on ACATS cc3305a
Date: Thu, 13 Feb 2014 13:00:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id`174

            Bug ID: 60174
           Summary: ICE on ACATS cc3305a
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: ada
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bernd.edlinger at hotmail dot de

BUILD cc3305a.adb
gnatmake --GCC="/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/xgcc
-B/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/" -gnatws -O2 -gnat95
-I/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/testsuite/ada/acats/support
cc3305a.adb -largs --GCC="/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/xgcc
-B/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/"
/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/xgcc -c
-B/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/ -gnatws -O2 -gnat95
-I/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/testsuite/ada/acats/support
cc3305a.adb

Unable to coalesce ssa_names 34 and 399 which are marked as MUST COALESCE.
i_34(ab) and  i_399(ab)
+===========================GNAT BUG DETECTED==============================+
| 4.9.0 20140209 (experimental) (armv7l-unknown-linux-gnueabihf) GCC error:|
| SSA corruption                                                           |
| Error detected around cc3305a.adb:35:1                                   |
| Please submit a bug report; see http://gcc.gnu.org/bugs.html.            |
| Use a subject line meaningful to you and us to track the bug.            |
| Include the entire contents of this bug box in the report.               |
| Include the exact gcc or gnatmake command that you entered.              |
| Also include sources listed below in gnatchop format                     |
| (concatenated together with no headers between files).                   |
+==========================================================================+

Please include these source files with error report
Note that list may not be accurate in some cases,
so please double check that the problem can still
be reproduced with the set of files listed.
Consider also -gnatd.n switch (see debug.adb).

/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/ada/rts/system.ads
cc3305a.adb
/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/testsuite/ada/acats/support/report.ads
/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/ada/rts/s-soflin.ads
/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/ada/rts/ada.ads
/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/ada/rts/a-except.ads
/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/ada/rts/s-parame.ads
/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/ada/rts/s-stalib.ads
/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/ada/rts/a-unccon.ads
/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/ada/rts/s-traent.ads
/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/ada/rts/s-stache.ads
/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/ada/rts/s-stoele.ads
/home/ed/gnu/gcc-build-arm-linux-gnueabihf/gcc/ada/rts/s-stoele.adb


raised TYPES.UNRECOVERABLE_ERROR : comperr.adb:432
gnatmake: "cc3305a.adb" compilation error
FAIL:   cc3305a

cat LAST_UPDATED
Obtained from SVN: trunk revision 207646