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<div>Hi,</div>
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<div>I have the following code:</div>
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<div> %a1<def> = COPY %a0<kill></div>
<div> ...</div>
<div> %a0h<def> = COPY %a1l</div>
<div> </div>
<div>, as input to MachineCopyPropagation.</div>
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<div>The second copy is illegally erased! This is wrong, because it is the low part of a1 that is copied to the high part of a0.</div>
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<div>At a first glance, it seems that </div>
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<div> if (!ReservedRegs.test(Def) &&</div>
<div> (!ReservedRegs.test(Src) || NoInterveningSideEffect(CopyMI, MI)) &&</div>
<div> (SrcSrc == Def || TRI->isSubRegister(SrcSrc, Def))) {</div>
<div> ... </div>
<div> (erase COPY)</div>
<div> </div>
<div>, should be extended to </div>
<div> </div>
<div>...</div>
<div> (SrcSrc == Def || (TRI->isSubRegister(SrcSrc, Def) && isMatchingSubRegIdx(%a0, %a0h, %a1, %a1l)))) {</div>
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<div>, where isMatchingSubRegIdx (or whatever) should make sure that this type of subreg motion is not missed.</div>
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<div>Or is there something else that I've missed, that would avoid the problem?</div>
<div> </div>
<div>/Jonas</div>
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<div> </div>
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