On 07/24/2015 04:41 PM, Manuel López-Ibáñez wrote:
On 25 July 2015 at 00:17, Patrick Palka <patr...@parcs.ath.cx> wrote:
On Fri, Jul 24, 2015 at 5:55 PM, Manuel López-Ibáñez
<lopeziba...@gmail.com> wrote:
Is there a PR for this particular test case? I am interested in
improving the uninit analysis for gcc 6 so this potentially seems up
my alley.
We do not warn because of the infamous PR18501 (probably the
-Wuninitialized bug with the highest number of duplicates), where CPP
removes the default SSA definition of n and simply returns 1
unconditionally. But fixing PR18501 may not be necessary to detect
this case (Clang does it before doing any optimization).
You don't have to move the warning to the FE to fix this bug. Go back to
my proposal from several years ago which has a warning analysis phase at
the start and the end of the optimization pipeline. It can catch this
because it gets a chance to analyze the code prior to the generate PHI
elimination.
There are other cases that would be better warned from the FE:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=19808
I haven't looked at any of these recently. But fundamentally you don't
have to move the warning into the front-end, you just have to move it to
the start of the optimization pipeline.
jeff
