<div dir="ltr"><br><div class="gmail_extra"><br><br><div class="gmail_quote">On Thu, Jul 31, 2014 at 12:28 AM, Adam Nemet <span dir="ltr"><<a href="mailto:anemet@apple.com" target="_blank">anemet@apple.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word"><br><div><div class=""><div>On Jul 30, 2014, at 10:56 PM, Pete Cooper <<a href="mailto:peter_cooper@apple.com" target="_blank">peter_cooper@apple.com</a>> wrote:</div>
<br><blockquote type="cite"><div style="word-wrap:break-word">Hi Adam<br><div><blockquote type="cite"><div>On Jul 30, 2014, at 10:28 PM, Adam Nemet <<a href="mailto:anemet@apple.com" target="_blank">anemet@apple.com</a>> wrote:</div>
<br><div><span style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;float:none;display:inline!important">Hi Pete,</span><br style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
<br style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
<span style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;float:none;display:inline!important">Just to clarify, are you proposing two things here? First, 0b… literals to have type bits<n> and second to allow bits<n> initializer to contain other bits<m> elements which would initialize the next m elements.</span><br style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
<br style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
</div></blockquote>Yeah, exactly those 2 things. I have them in separate patches, but I think we only get the benefit from sized binary literals if we also allow them to initialize multiple bits in another bits<n> type.</div>
</div></blockquote><div><br></div></div><div>Looks like bits<n> is already valid in a bits initializer context; it yields the bottom bit.</div><div><br></div><div><div>def a {</div><div> bits<2> opc = { 0, 1 };</div>
<div> bits<2> opc2 = { 1, 0 };</div><div> bits<2> oo = { opc, opc2 };</div><div>}</div><div><br></div><div>is valid and produces:</div><div><br></div><div>..</div><div> bits<2> oo = { 1, 0 };</div><div>
..</div><div><br></div><div>Are you aware of this? This may lead to some ambiguity with your proposed extension. (I have no idea whether this behavior is relied on anywhere though.)</div></div></div></div></blockquote><div>
<br></div><div>I think it would make sense to change this behavior to follow the behavior that Pete describes. I don't have the code handy but my guess is that what the code is doing here is requesting each element in the braces of a bits<n> initializer to be casted to `bit`; in that case, we would want to change that code to first try casting to bits and give that preference (and issues relevant diagnostics). Pete, is that what your patch does? Can you attach your patches?</div>
<div><br></div><div>Of course, before changing the behavior, we would probably want to place an assert on that codepath to catch all existing cases where the behavior would change.</div><div>Also it is important to scan all the docs in docs/TableGen/ and make any necessary updates (if there is nowhere that needs to be updated, then documentation needs to be *added* covering this behavior).</div>
<div>Finally, we should post a notice to LLVMdev for out-of-tree maintainers including information about how to add the necessary assert to check for places where this behavior would change their .td files.</div><div><br>
</div><div>-- Sean Silva</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word"><div><div><span class="HOEnZb"><font color="#888888"><div>
<br></div><div>Adam</div></font></span></div><div class=""><br><blockquote type="cite"><div style="word-wrap:break-word"><div><br></div><div>Thanks,</div><div>Pete<br><blockquote type="cite"><span style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;float:none;display:inline!important">I.e. I don’t think we currently accept:</span><br style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
<br style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
<span style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;float:none;display:inline!important">bits<4> x = { opc, opc }</span><br style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
<br style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
<span style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;float:none;display:inline!important">Thanks,</span><br style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
<span style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;float:none;display:inline!important">Adam</span></blockquote>
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