[PATCH] tree-ssa-uninit: suppress more spurious warnings

Alexander Monakov amonakov@ispras.ru
Fri May 17 16:59:00 GMT 2019


On Fri, 17 May 2019, Jeff Law wrote:

> So my question is are these showing up in practice?  The gimple based
> tests seem to be skipping the optimizers that would have eliminated this
> stuff.
> 
> In each of the testcases I would have expected jump threading to have
> eliminated the problematical path through the CFG.

If there's anything slightly complicated, like say a loop, between the
(lack of) definition and the use, optimizations won't be able to simplify
the flow and the false positive/negative can be seen.

In fact Vlad's first patch submission used a trivial loop in a C testcase
alongside a minimized gimple testcase to showcase how this happens:
https://gcc.gnu.org/ml/gcc-patches/2019-04/msg00040.html

Alexander



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