Re: [PATCH 1/1] s390/dasd: fix string length handling

[Nick Desaulniers]

On Mon, Aug 28, 2023 at 05:18:37PM +0000, David Laight wrote:
> From: Heiko Carstens
> > Sent: 28 August 2023 16:32
> >  	if (strlen(uid.vduit) > 0)
> 
> Does the compiler know enough to optimise that brain-dead test?
> 

For the purposes of skipping diagnostics, no; clang performs semantic
analysis BEFORE optimization (which is handled by LLVM). As such, clang
will produce diagnostics on dead code.

Partly because LLVM isn't very ergonomic at emitting diagnostics from
the backend, partly because Clang code owner and developers don't want
clang to emit diagnostics dependent on optimization level.

I disagree with my compatriots, and you can read more thoughts here:
https://discourse.llvm.org/t/rfc-improving-clangs-middle-and-back-end-diagnostics/69261?u=nickdesaulniers