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<p class="MsoNormal">Hi,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">At the moment the vectorize_width(X) #pragma is used to provide hints to LLVM<o:p></o:p></p>
<p class="MsoNormal">about which vectorisation factor to use. The unsigned argument ‘X’ used to match<o:p></o:p></p>
<p class="MsoNormal">the NumElements property in the VectorType class, however VectorType is now<o:p></o:p></p>
<p class="MsoNormal">defined in terms of a ElementCount class.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I’d like to propose an extension to the vectorize_width #pragma that now takes<o:p></o:p></p>
<p class="MsoNormal">an optional second parameter of ‘fixed’ or ‘scalable’ that matches up with<o:p></o:p></p>
<p class="MsoNormal">ElementCount. When not specified the default value would be ‘fixed’. A few<o:p></o:p></p>
<p class="MsoNormal">examples of how this would look like are shown below:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoPlainText"> // Vectorize the loop with <4 x eltty><o:p></o:p></p>
<p class="MsoPlainText"> #pragma clang loop vectorize_width(4)<o:p></o:p></p>
<p class="MsoPlainText"> #pragma clang loop vectorize_width(4, fixed)<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText"> // Vectorize the loop with <vscale x 4 x eltty><o:p></o:p></p>
<p class="MsoPlainText"> #pragma clang loop vectorize_width(4, scalable)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">As a further extension I’d also like to permit vectorize_width(fixed|scalable) to<o:p></o:p></p>
<p class="MsoNormal">allow users to hint at the type of vector used without specifying the<o:p></o:p></p>
<p class="MsoNormal">vectorisation factor. Examples of this would be:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoPlainText"> // Vectorize the loop with <N x eltty> for a profitable N<o:p></o:p></p>
<p class="MsoPlainText"> #pragma clang loop vectorize_width(fixed)<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText"> // Vectorize the loop with <vscale x N x eltty> for a profitable N<o:p></o:p></p>
<p class="MsoPlainText"> #pragma clang loop vectorize_width(scalable)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Any thoughts you have would be much appreciated!<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Kind Regards,<o:p></o:p></p>
<p class="MsoNormal">David Sherwood.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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