<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><blockquote type="cite"><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">Hi Nick,</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 13px/normal Courier; min-height: 16px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">><i> Just as a quick recap the problem I encountered is how to deal </i></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">><i> instructions in a block being used as operands in the unwind dest. Such </i></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">><i> as this:</i></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">><i> </i></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">><i> bb1: unwinds to %cleanup</i></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">><i> call void @foo() ; might throw, might not</i></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">><i> %x = add i32 %y, %z</i></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">><i> call void @foo() ; might throw, might not</i></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">><i> ret void</i></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">><i> cleanup:</i></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">><i> call void @use(i32 %x)</i></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">><i> </i></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">><i> The problem is that %x might not have been executed before we enter </i></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">><i> %cleanup.</i></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 13px/normal Courier; min-height: 16px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">how about just declaring this illegal? i.e. require the first call</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">to be in a different basic block to the second, making it possible</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">to use a phi node in %cleanup.</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 13px/normal Courier; min-height: 16px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">Ciao,</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 13px/normal Courier; min-height: 16px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Courier" size="4" style="font: 13.0px Courier">Duncan.</font></div></blockquote></div><div><font class="Apple-style-span" face="Courier" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><font class="Apple-style-span" face="Courier" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><font class="Apple-style-span" face="Courier" size="3"><span class="Apple-style-span" style="font-size: 13px;">I pretty much support your opinion Duncan. Unwind</span></font></div><div><font class="Apple-style-span" face="Courier" size="3"><span class="Apple-style-span" style="font-size: 13px;">BBs should not mess with values defined by their worker</span></font></div><div><font class="Apple-style-span" face="Courier" size="3"><span class="Apple-style-span" style="font-size: 13px;">BB. We should not introduce undefined behaviour intentionally.</span></font></div><div><font class="Apple-style-span" face="Courier" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><font class="Apple-style-span" face="Courier" size="3"><span class="Apple-style-span" style="font-size: 13px;"><span class="Apple-tab-span" style="white-space:pre"> </span>Gabor<br></span></font></div><div><font class="Apple-style-span" face="Courier" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div>
</body></html>