<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><div><div>On 1-Apr-09, at 12:42 PM, Nicolas Capens wrote:</div><blockquote type="cite"><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div lang="EN-US" link="blue" vlink="purple" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div class="Section1"><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Hi Stefanus,<o:p></o:p></span></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Thanks for the info. I still think it’s a bug though. Take for example a case where the vectors each have four elements. The values in Mask[] can range from 0 to 7, while HLSMask only has 4 elements. So LHSMask[Mask[i]] can go out of bounds, no?</span></div></div></div></span></blockquote><div><br></div>Good point! One easy way to fix this would be to use: </div><div><br></div><div>if (Mask[i] >= e) {</div><div><br></div><div>instead. The code could also be improved to consider the new mask equal to lhsmask/mask in places where they both refer to undefined elements.</div><div><br></div><div>Stefanus</div><div><div><br><div></div></div><blockquote type="cite"><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div lang="EN-US" link="blue" vlink="purple" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div class="Section1"><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p></o:p></span></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span class="Apple-style-span" style="font-family: Calibri; font-size: 15px; color: rgb(31, 73, 125); ">Cheers,</span></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Nicolas<o:p></o:p></span></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div><div style="border-right-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-top-style: solid; border-top-color: rgb(181, 196, 223); border-top-width: 1pt; padding-top: 3pt; padding-right: 0in; padding-bottom: 0in; padding-left: 0in; "><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; ">From:</span></b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; "><span class="Apple-converted-space"> </span><a href="mailto:llvmdev-bounces@cs.uiuc.edu">llvmdev-bounces@cs.uiuc.edu</a> [<a href="mailto:llvmdev-bounces@cs.uiuc.edu" style="color: blue; text-decoration: underline; ">mailto:llvmdev-bounces@cs.uiuc.edu</a>]<span class="Apple-converted-space"> </span><b>On Behalf Of<span class="Apple-converted-space"> </span></b>Stefanus Du Toit<br><b>Sent:</b><span class="Apple-converted-space"> </span>woensdag 1 april 2009 16:31<br><b>To:</b><span class="Apple-converted-space"> </span>LLVM Developers Mailing List<br><b>Subject:</b><span class="Apple-converted-space"> </span>Re: [LLVMdev] Shuffle combine<o:p></o:p></span></div></div></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; ">Hi Nicolas,<o:p></o:p></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div><div><div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; ">On 1-Apr-09, at 7:34 AM, Nicolas Capens wrote:<o:p></o:p></div></div><blockquote style="margin-top: 5pt; margin-bottom: 5pt; "><div><div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: black; ">I’m having some trouble understanding the following lines in InstructionCombining.cpp, which possibly contain a bug:<o:p></o:p></span></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: black; "> <o:p></o:p></span></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 10pt; font-family: 'Courier New'; color: blue; ">if</span><span class="apple-converted-space"><span style="font-size: 10pt; font-family: 'Courier New'; color: black; "> </span></span><span style="font-size: 10pt; font-family: 'Courier New'; color: black; ">(Mask[i] >= 2*e)</span><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: black; "><o:p></o:p></span></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 10pt; font-family: 'Courier New'; color: black; "> NewMask.push_back(2*e);</span><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: black; "><o:p></o:p></span></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 10pt; font-family: 'Courier New'; color: blue; ">else</span><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: black; "><o:p></o:p></span></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 10pt; font-family: 'Courier New'; color: black; "> NewMask.push_back(LHSMask[Mask[i]]);</span><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: black; "><o:p></o:p></span></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: black; "> <o:p></o:p></span></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: black; ">When Mask[i] is bigger than the size of LHSMask it reads out of bounds on that last line. I believe the first line is there to try to prevent that but then it should be comparing to LHSMask.size() not 2*e (e being Mask.size()). <o:p></o:p></span></div></div></div></div></blockquote><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; ">Upon quick inspection of the code, I don't think this is necessarily a bug right now, but the function could be improved.<o:p></o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; ">I believe this stems (in part at least) from the fact that shufflevector used to require that the sources and the mask have the same size, which was changed a few months ago to allow an arbitrarily-sized mask.<o:p></o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; ">This would be a bug all throughout this function (which generally assumes this is still the case), if the function didn't do the following check early:<o:p></o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "> unsigned VWidth = cast<VectorType>(SVI.getType())->getNumElements();<o:p></o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "> if (VWidth != cast<VectorType>(LHS->getType())->getNumElements())<o:p></o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "> return 0;<o:p></o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; ">In other words, if the mask size is not equal to the number of elements in the vectors, it skips this transformation.<o:p></o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; ">Because the LHS is a shufflevector in the part of the code you are mentioning, and the result of a shufflevector has the same number of elements as its mask, you are actually guaranteed that LHSMask.size() == Mask.size(), because LHSMask.size() == LHS->getNumElements() == Mask.size().<o:p></o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; ">It shouldn't be too hard to relax the constraint that this optimization requires the number of elements being shuffle to be equal to the mask size, but it'll probably take some careful testing!<o:p></o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; ">Stefanus<o:p></o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div></div><div><div><div><div><div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 9pt; font-family: Helvetica, sans-serif; color: black; ">--<o:p></o:p></span></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 9pt; font-family: Helvetica, sans-serif; color: black; ">Stefanus Du Toit <<a href="mailto:stefanus.dutoit@rapidmind.com" style="color: blue; text-decoration: underline; ">stefanus.dutoit@rapidmind.com</a>><o:p></o:p></span></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 9pt; font-family: Helvetica, sans-serif; color: black; "> RapidMind Inc.<o:p></o:p></span></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 9pt; font-family: Helvetica, sans-serif; color: black; "> phone: +1 519 885 5455 x116 -- fax: +1 519 885 1463<o:p></o:p></span></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 9pt; font-family: Helvetica, sans-serif; color: black; "><o:p> </o:p></span></div></div></div></div></div></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div></div><span><ATT00001.txt></span></div></div></span></blockquote></div><br><div apple-content-edited="true"> <span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>--</div><div>Stefanus Du Toit <<a href="mailto:stefanus.dutoit@rapidmind.com">stefanus.dutoit@rapidmind.com</a>></div><div> RapidMind Inc.</div><div> phone: +1 519 885 5455 x116 -- fax: +1 519 885 1463</div><div><br class="khtml-block-placeholder"></div></div></div></div></div></span><br class="Apple-interchange-newline"> </div><br></div></body></html>