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<div>We also had quad registers defined in function of 4 single registers, then we couldn't extract paired register from it easily.</div>
<div>So we changed and made them defined in function of paired registers. We also named the sub indices as to know what size of sub-register we want. Is something alike this:</div>
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<div>// Defining sub-register indexes</div>
<div>def sub_p0 : SubRegIndex<128, 0>;</div>
<div>def sub_p1 : SubRegIndex<128,128>;</div>
<div> </div>
<div>def sub_s0 : SubRegIndex<64, 0>;</div>
<div>def sub_s1 : SubRegIndex<64, 64>;</div>
<div>def sub_s2 : ComposedSubRegIndex<sub_p1, sub_s0>;</div>
<div>def sub_s3 : ComposedSubRegIndex<sub_p1, sub_s1>;</div>
<div> </div>
<div>// Composed register classes</div>
<div>
<div>// Paired Registers</div>
<div>class PGR<string n, list<Register> subregs></div>
<div> : : RegisterWithSubRegs<n, subregs> {</div>
<div> let SubRegIndices = [sub_s0, sub_s1];</div>
<div>}</div>
<div> </div>
<div>// Quad Register</div>
<div>
<div>class QGR<string n, list<Register> subregs></div>
<div> : RegisterWithSubRegs<n, subregs> {</div>
<div> let SubRegIndices = [sub_p0, sub_p1];</div>
<div>}</div>
<div> </div>
<div>// Defining registers</div>
<div>def P0 : PGR< 0, "$r0r1", [ R0, R1]>;</div>
<div>def P2 : PGR< 2, "$r2r3", [ R2, R3]>;</div>
<div>....</div>
<div> </div>
</div>
</div>
<div>def Q0 : QGR< 0, "$r0r1r2r3", [ P0, P2]>;</div>
<div> </div>
<div>//</div>
<div>Now can use any of those 6 sub-index to reference 2 sub-pair registers or any of the 4 single registers.</div>
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<blockquote style="margin: 0 0 0 0.8em; border-left: 1px #ccc solid; padding-left: 1em;"><hr id="MESSAGE_DATA_MARKER"><strong>From: </strong>Fraser <llvm-dev@lists.llvm.org><br><strong>To: </strong>jackie <jackie_linzz@126.com><br><strong>Cc: </strong>llvm-dev <llvm-dev@lists.llvm.org><br><strong>Date: </strong>Tuesday, 10 August 2021 2:15 PM CEST<br><strong>Subject: </strong>Re: [llvm-dev] How to define subreg relationship in td file?<br><br>Hi,<br><br>You can (I'm hesitant to say you "must") model this with extra "fake"<br>(in some sense) physical registers which represent the paired and<br>quadrupled registers. This will also tell the register allocator that<br>allocating VRPair0 will clobber both VR0 *and VR1*, for example.<br><br>So you have half the number of VRPair registers which each have two VRs<br>as subregisters, then half that again of VRQuad registers which have<br>two VRPairs as subregisters. The subregister properties will apply<br>transitively so your VRQuads will have four VR subregisters using<br>composed subregister indices which LLVM will either automatically infer<br>or you can specify yourself with ComposedSubRegIndex.<br><br>Take a look at RISCVRegisterInfo.td for inspriation. Each vector V<br>register is paired into VM2 which are in turn paried into VM4s and then<br>into VM8s.<br><br>Cheers,<br>Fraser<br><br>On Tue, 2021-08-10 at 19:54 +0800, 林政宗 via llvm-dev wrote:<br>> Hi, there.<br>> <br>> I met a problem about defining SubReg relationship when defining<br>> Registers in td file.<br>> The target has a kind of vector register named VR which is of type<br>> v4f32. <br>> 2 VR makes 1 DVR. 4 VR makes 1 QVR.<br>> I have some code like this:<br>> -------------------------------------------------------------------<br>> -----------------------------------<br>> def VRPairs : RegisterTuples<[vsub_0, vsub_1],<br>> [(decimate (rotl VRegs, 0), 2),<br>> (decimate (rotl VRegs, 1), 2)],<br>> []>;<br>> <br>> def VRQuads : RegisterTuples<[vsub_0, vsub_1, vsub_2, vsub_3],<br>> [(decimate (rotl VRegs, 0), 4),<br>> (decimate (rotl VRegs, 1), 4),<br>> (decimate (rotl VRegs, 2), 4),<br>> (decimate (rotl VRegs, 3), 4)],<br>> []>;<br>> def DVRRegs : RegisterClass<"xxx", [v8f32], 256, (add VRPairs)>;<br>> <br>> def QVRRegs : RegisterClass<"xxx", [v16f32], 512, (add VRQuads)>;<br>> -------------------------------------------------------------------<br>> -----------------------------------<br>> But also, 2 DVR makes 1 QVR. QVR has two subregs, each of which is 1<br>> DVR.<br>> How can I describe the SubReg relationship between DVR and QVR? <br>> Could anyone help? Thanks in advance!<br>> <br>> <br>> BR,<br>> Jerry<br>> <br>> <br>> <br>> <br>> <br>> _______________________________________________<br>> LLVM Developers mailing list<br>> <a href="mailto:llvm-dev@lists.llvm.org" target="_blank" rel="noopener noreferrer">llvm-dev@lists.llvm.org</a><br>> <br>> <a href="https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev" target="_blank" rel="noopener noreferrer">https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a><br>> <br><br>_______________________________________________<br>LLVM Developers mailing list<br><a href="mailto:llvm-dev@lists.llvm.org" target="_blank" rel="noopener noreferrer">llvm-dev@lists.llvm.org</a><br><a href="https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev" target="_blank" rel="noopener noreferrer">https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a><br>
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