<div dir="ltr">I agree with the sentiment: without a usable backend bit-rot will surely ensue. I guess ideally the patches would accompany a real backend relying upon them and a target environment executing them, e.g. a simulator environment for the DSP so access to the real hardware isn't required.<div><br></div><div>FWIW my original curiosity stems from wondering whether a C/C++ compiler can even be created for a non-mainstream architecture such as Knuth's original MIX (<a href="http://en.wikipedia.org/wiki/MIX" target="_blank">http://en.wikipedia.org/wiki/MIX</a> - given such features as a byte size that isn't aligned to the memory word size of 6-bit bytes, 31-bit words, so a char pointer effectively requires padding for the p[5] case of bit-30). But if a MIX backend was created then at least execution environments exist for it - however I guess a very real question for the community clang/llvm would be whether the additional complexity for supporting such a "toy environment" is warranted, especially since MIX was superseded by MMIX (which has a gcc backend).</div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Mar 10, 2015 at 5:09 PM, Reid Kleckner <span dir="ltr"><<a href="mailto:rnk@google.com" target="_blank">rnk@google.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">It's definitely doable, but I'd be worried about the maintenance burden. Beyond contributing the initial patches, I'd want to see a maintenance commitment and relatively comprehensive tests that can be run upstream.<div><br></div><div>For example, if there were an i24 MVT, how would I test my target independent SDAG change that operates on all integer values? Currently, our answer to that question is "find a backend that uses it and test that". Without such a backend, it's hard for us to promise that this support will continue to work.</div></div><div class="gmail_extra"><br><div class="gmail_quote"><div><div class="h5">On Tue, Mar 10, 2015 at 3:12 AM, Tyro Software <span dir="ltr"><<a href="mailto:softwaretyro@gmail.com" target="_blank">softwaretyro@gmail.com</a>></span> wrote:<br></div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="h5"><div dir="ltr"><div style="font-size:12.8000001907349px">Back in 2009 there was some discussion of the practicality of supporting char sizes greater than 8-bit:<br></div><div style="font-size:12.8000001907349px"><br></div><div style="font-size:12.8000001907349px"><div><a href="http://lists.cs.uiuc.edu/pipermail/cfe-dev/2009-September/thread.html#6349" target="_blank">http://lists.cs.uiuc.edu/pipermail/cfe-dev/2009-September/thread.html#6349</a></div><div><a href="http://lists.cs.uiuc.edu/pipermail/llvmdev/2009-September/thread.html#26025" target="_blank">http://lists.cs.uiuc.edu/pipermail/llvmdev/2009-September/thread.html#26025</a></div></div><div style="font-size:12.8000001907349px"><br></div><div style="font-size:12.8000001907349px">with the consensus seemingly being "quite doable, please get a good patch and submit".</div><div style="font-size:12.8000001907349px"><br></div><div style="font-size:12.8000001907349px">However the current code appears (to my neophyte eyes) to be explicitly 8-bit, e.g. one instance called out in the mail thread remains:</div><div style="font-size:12.8000001907349px"><br></div><div style="font-size:12.8000001907349px"><div>/// isString - This method returns true if this is an array of i8.</div><div>bool ConstantDataSequential::isString() const {</div><div> return isa<ArrayType>(getType()) && getElementType()->isIntegerTy(8);</div><div>}</div></div><div style="font-size:12.8000001907349px"><br></div><div style="font-size:12.8000001907349px">I didn't find anything related beyond this mail thread such as a discussion of a patch but of course I might be searching too narrowly - perhaps someone here can recall whether it went any further, whether insurmountable barriers do exist, etc?</div><div style="font-size:12.8000001907349px"><br></div><div style="font-size:12.8000001907349px">Thanks for whatever advice & thread necromancy you can offer,</div><div style="font-size:12.8000001907349px">Tyro</div></div>
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