[cfe-dev] RFC: Implementing -fno-delete-null-pointer-checks in clang

Tim Northover via cfe-dev cfe-dev at lists.llvm.org
Wed Apr 18 11:21:16 PDT 2018


On 18 April 2018 at 18:13, Manoj Gupta via cfe-dev
<cfe-dev at lists.llvm.org> wrote:
> Therefore, I would like to implement support for this flag (maybe with a
> different name),

I'd suggest -mdo-what-i-mean; the whole idea is horribly
underspecified, and basically rips up the LangRef in favour of a
nebulous set of good and bad optimizations (probably as dictated by
the ones that have bitten someone who wrote bad code recently and was
grumpy enough about it to complain at us).

In particular I'm skeptical that the address space solution actually
works. What they actually mean is probably not so much about removing
the icmps, but about the control-flow decisions based on them. And
LLVM might not be aware that any given conditional branch comes from a
tainted comparison.

Cheers.

Tim.


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