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<p class="MsoNormal">Is the question just “why is SDNode::NumOperands unsigned short?” It’s to save a bit of memory: two “unsigned short” values are 4 bytes, where two “size_t” values would be 16 bytes. Not sure how much it realistically matters; I don’t
think anyone has really tried to evaluate the performance impact of changing that.<o:p></o:p></p>
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<p class="MsoNormal">-Eli<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><b>From:</b> llvm-dev <llvm-dev-bounces@lists.llvm.org>
<b>On Behalf Of </b>YoungJun Lee via llvm-dev<br>
<b>Sent:</b> Tuesday, May 26, 2020 8:04 PM<br>
<b>To:</b> llvm-dev@lists.llvm.org<br>
<b>Subject:</b> [EXT] [llvm-dev] Why limit to the 64k on the number of SDNode operands in SelectionDAG?<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Hi, all<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Why limit to the 64k on the number of SDNode operands in "Selection::createOperands()"?<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">If it has over the 64k on the number of SDNode, it occurs the assertion. <o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">This commit is related the contents on above. <o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><a href="https://github.com/llvm/llvm-project/commit/814a6794ba78ad52da499c67792602873e43d4f8">[SelectionDAG] Split very large token factors for loads into 64k chunks</a><o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Also, the return value type of "SDNode::getMaxNumOperands" function is "size_t", but really the return value type is fixed "unsigned short" because the type of "SDNode::NumOperands" is "unsigned short".<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">This commit is related the contents on above. <o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><a href="https://github.com/llvm/llvm-project/commit/1b8177232813a048407bbb43eef18d7f72794b35">[SelectionDAG] Add static getMaxNumOperands function to SDNode.</a><o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Thanks.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Best Regards.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">-- <o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Young Jun Lee [dog3hk]<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Tel : +82 010 3129 2621<o:p></o:p></p>
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