<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"> <head> <meta http-equiv="Content-Type" content="text/html; charset=us-ascii"> <meta name="Generator" content="Microsoft Word 14 (filtered medium)"> <style></style> </head> <body lang="ZH-CN" link="blue" vlink="purple"> <div class="WordSection1"> <p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D">Good question, let me explain a little more.<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D">For a spilled virtual register, it will not have a dedicated physical register for it anymore. And its real data lies in scratch memory.<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D">When a virtual register is used, it will be always reloaded from scratch memory. when it is updated, it will be written to scratch memory immediately.<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D">The content of the reserved register is only valid for one instruction(not including spill/unspill instruction). In the next instruction, it will be used to store other data.<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p> <p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> zhigang gong [mailto:zhigang.gong@gmail.com] <br> <b>Sent:</b> Friday, August 09, 2013 5:02 PM<br> <b>To:</b> Song, Ruiling<br> <b>Cc:</b> beignet@lists.freedesktop.org<br> <b>Subject:</b> Re: [Beignet] [PATCH 2/2] Skip spill/unspill instruction when trying to do spill.<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p> <div> <p class="MsoNormal"><span lang="EN-US">On Fri, Aug 9, 2013 at 4:38 PM, Song, Ruiling <<a href="mailto:ruiling.song@intel.com" target="_blank">ruiling.song@intel.com</a>> wrote:<o:p></o:p></span></p> <div> <div> <blockquote style="border:none;border-left:solid #CCCCCC 1.0pt;padding:0cm 0cm 0cm 6.0pt;margin-left:4.8pt;margin-right:0cm"> <div> <div> <p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D">When I do a spill, I directly construct a physical register, see below:</span><span lang="EN-US"><o:p></o:p></span></p> <p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D">spill->src(0) =GenRegister(GEN_GENERAL_REGISTER_FILE, dstStart + dstID, 0,</span><span lang="EN-US"><o:p></o:p></span></p> <p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D"> selReg.type, selReg.vstride, selReg.width, selReg.hstride);</span><span lang="EN-US"><o:p></o:p></span></p> <p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D">and also allocate one physical register from reserved register pool, change the spilled virtual register to physical register:</span><span lang="EN-US"><o:p></o:p></span></p> <p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D">dst.physical =1; <a href="http://dst.nr" target="_blank">dst.nr</a> = dstStart+dstID; dst.subnr = 0;</span><span lang="EN-US"><o:p></o:p></span></p> <p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D">so, in later emit code, when they call ra->genReg(), I will directly return the physical register; see GenRegAllocator::Opaque::genReg()</span><span lang="EN-US"><o:p></o:p></span></p> </div> </div> </blockquote> <div> <p class="MsoNormal"><span lang="EN-US"> Sounds good. But if my understanding is correct, then after spill or unspill, the spilledReg will become a physical<o:p></o:p></span></p> </div> <div> <p class="MsoNormal"><span lang="EN-US"> register:<o:p></o:p></span></p> </div> <div> <div> <p class="MsoNormal"><span lang="EN-US"> // change nr/subnr, keep other register settings<o:p></o:p></span></p> </div> <div> <p class="MsoNormal"><span lang="EN-US"> <a href="http://src.nr">src.nr</a> = srcStart+srcID; src.subnr=0; src.physical=1;<o:p></o:p></span></p> </div> <div> <p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p> </div> <div> <div> <p class="MsoNormal"><span lang="EN-US"> // change nr/subnr, keep other register settings<o:p></o:p></span></p> </div> <div> <p class="MsoNormal"><span lang="EN-US"> dst.physical =1; <a href="http://dst.nr"> dst.nr</a> = dstStart+dstID; dst.subnr = 0;<o:p></o:p></span></p> </div> </div> <div> <p class="MsoNormal"><span lang="EN-US"> And the most important side effect is that the reserved registers will be used.<o:p></o:p></span></p> </div> <div> <p class="MsoNormal"><span lang="EN-US"> Then latter, if we want to spill another register, then it may use the reserved registers again but those registers are already used by the<o:p></o:p></span></p> </div> <div> <p class="MsoNormal"><span lang="EN-US"> previous spilled register.<o:p></o:p></span></p> </div> <div> <p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p> </div> <div> <p class="MsoNormal"><span lang="EN-US"> Is it a problem?<o:p></o:p></span></p> </div> <div> <p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p> </div> </div> <blockquote style="border:none;border-left:solid #CCCCCC 1.0pt;padding:0cm 0cm 0cm 6.0pt;margin-left:4.8pt;margin-right:0cm"> <div> <div> <p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><span lang="EN-US"><o:p></o:p></span></p> <p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> beignet-bounces+ruiling.song=<a href="mailto:intel.com@lists.freedesktop.org" target="_blank">intel.com@lists.freedesktop.org</a> [mailto:<a href="mailto:beignet-bounces%2Bruiling.song" target="_blank">beignet-bounces+ruiling.song</a>=<a href="mailto:intel.com@lists.freedesktop.org" target="_blank">intel.com@lists.freedesktop.org</a>] <b>On Behalf Of </b>zhigang gong<br> <b>Sent:</b> Friday, August 09, 2013 4:29 PM<br> <b>To:</b> Song, Ruiling<br> <b>Cc:</b> <a href="mailto:beignet@lists.freedesktop.org" target="_blank">beignet@lists.freedesktop.org</a><br> <b>Subject:</b> Re: [Beignet] [PATCH 2/2] Skip spill/unspill instruction when trying to do spill.</span><span lang="EN-US"><o:p></o:p></span></p> <div> <div> <p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> <o:p></o:p></span></p> <div> <div> <p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">Could you tell something more about how could a spilledReg be a physical register?<o:p></o:p></span></p> </div> <div> <p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">This is not very clear for me. If a virtual register is to be spilled, then it will<o:p></o:p></span></p> </div> <div> <p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">always be a virtual register, and will be unspilled when it is used. When it may<o:p></o:p></span></p> </div> <div> <p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">become a physical register?<o:p></o:p></span></p> </div> <div> <p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> <o:p></o:p></span></p> </div> </div> <div> <p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:12.0pt"><span lang="EN-US"> <o:p></o:p></span></p> <div> <p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">On Fri, Aug 9, 2013 at 1:23 PM, Ruiling Song <<a href="mailto:ruiling.song@intel.com" target="_blank">ruiling.song@intel.com</a>> wrote:<o:p></o:p></span></p> <p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">We can only spill virtual registers, should skip physical register.<br> This fix random failure of compiler_box_blur when do spilling.<br> <br> Signed-off-by: Ruiling Song <<a href="mailto:ruiling.song@intel.com" target="_blank">ruiling.song@intel.com</a>><br> ---<br> backend/src/backend/gen_insn_selection.cpp | 7 +++++--<br> 1 file changed, 5 insertions(+), 2 deletions(-)<br> <br> diff --git a/backend/src/backend/gen_insn_selection.cpp b/backend/src/backend/gen_insn_selection.cpp<br> index 3610051..5cafa98 100644<br> --- a/backend/src/backend/gen_insn_selection.cpp<br> +++ b/backend/src/backend/gen_insn_selection.cpp<br> @@ -628,12 +628,15 @@ namespace gbe<br> <br> for (auto &block : blockList)<br> for (auto &insn : block.insnList) {<br> + // spill / unspill insn should be skipped when do spilling<br> + if(insn.opcode == SEL_OP_SPILL_REG || insn.opcode == SEL_OP_UNSPILL_REG) continue;<br> +<br> const uint32_t srcNum = insn.srcNum, dstNum = insn.dstNum;<br> <br> for (uint32_t srcID = 0; srcID < srcNum; ++srcID) {<br> const GenRegister selReg = insn.src(srcID);<br> const ir::Register reg = selReg.reg();<br> - if(selReg.file == GEN_GENERAL_REGISTER_FILE && reg == spilledReg) {<br> + if(reg == spilledReg && selReg.file == GEN_GENERAL_REGISTER_FILE && selReg.physical == 0) {<br> GBE_ASSERT(srcID < 5);<br> SelectionInstruction *unspill = this->create(SEL_OP_UNSPILL_REG, 1, 0);<br> unspill->state = GenInstructionState(simdWidth);<br> @@ -652,7 +655,7 @@ namespace gbe<br> for (uint32_t dstID = 0; dstID < dstNum; ++dstID) {<br> const GenRegister selReg = insn.dst(dstID);<br> const ir::Register reg = selReg.reg();<br> - if(selReg.file == GEN_GENERAL_REGISTER_FILE && reg == spilledReg) {<br> + if(reg == spilledReg && selReg.file == GEN_GENERAL_REGISTER_FILE && selReg.physical == 0) {<br> GBE_ASSERT(dstID < 5);<br> SelectionInstruction *spill = this->create(SEL_OP_SPILL_REG, 0, 1);<br> spill->state = GenInstructionState(simdWidth);<br> <span style="color:#888888">--<br> 1.7.9.5<br> <br> _______________________________________________<br> Beignet mailing list<br> <a href="mailto:Beignet@lists.freedesktop.org" target="_blank">Beignet@lists.freedesktop.org</a><br> <a href="http://lists.freedesktop.org/mailman/listinfo/beignet" target="_blank">http://lists.freedesktop.org/mailman/listinfo/beignet</a></span><o:p></o:p></span></p> </div> <p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> <o:p></o:p></span></p> </div> </div> </div> </div> </div> </blockquote> </div> <p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p> </div> </div> </div> </body> </html>