<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hi Daniel, Paul<div class=""><br class=""></div><div class="">Thanks for looking in to this. I think its great to fix the inconsistency here.</div><div class=""><br class=""></div><div class="">...<br class=""><div><blockquote type="cite" class=""><div class="">On Nov 18, 2015, at 2:19 AM, Daniel Sanders via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" class="">llvm-dev@lists.llvm.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="WordSection1" style="page: WordSection1; font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">><span class="Apple-converted-space"> </span><span lang="EN-US" class="">-----Original Message-----</span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">><span class="Apple-converted-space"> </span><span lang="EN-US" class="">From: Robinson, Paul [<a href="mailto:Paul_Robinson@playstation.sony.com" style="color: purple; text-decoration: underline;" class="">mailto:Paul_Robinson@playstation.sony.com</a>]</span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">><span class="Apple-converted-space"> </span><span lang="EN-US" class="">Sent: 17 November 2015 22:58</span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">><span class="Apple-converted-space"> </span><span lang="EN-US" class="">To: Daniel Sanders;<span class="Apple-converted-space"> </span><a href="mailto:llvm-dev@lists.llvm.org" style="color: purple; text-decoration: underline;" class="">llvm-dev@lists.llvm.org</a></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">><span class="Apple-converted-space"> </span><span lang="EN-US" class="">Subject: RE: Mips unconditionally uses fast-isel?</span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">><span class="Apple-converted-space"> </span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">> > > The other thing that might work, is having TargetMachine remember how</div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">> > > the fast-isel option got set, and make OptLevelChanger do the right</div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">> > > thing. But that seems like a hack to work around Mips not obeying the</div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">> > > specified optimization level, honestly.</div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">> ></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">> > I think we should do that as well. I don't think it's right that optnone</div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">> > enables Fast ISel even when it's been explicitly disabled. It should do</div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">> > the same checks as addPassesToGenerateCode() does.</div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">><span class="Apple-converted-space"> </span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">> Hm? What you're asking for is that "-O2" and "-O2 -fast-isel=none" are</div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">> identical, unless you have an 'optnone' function. Do you really have a</div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">> use-case for controlling the codegen path for an 'optnone' function?</div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">> The whole point of 'optnone' is to avoid optimizations.</div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">> --paulr</div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">><span class="Apple-converted-space"> </span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">No, that's already true. -O2 doesn't try to enable Fast ISel (unless the optnone attribute is given) so –fast-isel=false has no effect.<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">I'm saying that optnone means 'use –O0 for this function' and that optnone should<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">respect non-default values of the -fast-isel flag like –O0 does. This is the behaviour I'd expect:<o:p class=""></o:p></span></div><table class="MsoTableGrid" border="1" cellspacing="0" cellpadding="0" style="border-collapse: collapse; border: none;"><tbody class=""><tr class=""><td width="161" valign="top" style="width: 120.5pt; border: 1pt solid windowtext; background-color: rgb(217, 217, 217); padding: 0cm 5.4pt; background-position: initial initial; background-repeat: initial initial;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class=""><o:p class=""> </o:p></span></div></td><td width="131" valign="top" style="width: 98.55pt; border-style: solid solid solid none; border-top-color: windowtext; border-right-color: windowtext; border-bottom-color: windowtext; border-top-width: 1pt; border-right-width: 1pt; border-bottom-width: 1pt; background-color: rgb(217, 217, 217); padding: 0cm 5.4pt; background-position: initial initial; background-repeat: initial initial;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">-fast-isel=false<o:p class=""></o:p></span></div></td><td width="122" valign="top" style="width: 91.8pt; border-style: solid solid solid none; border-top-color: windowtext; border-right-color: windowtext; border-bottom-color: windowtext; border-top-width: 1pt; border-right-width: 1pt; border-bottom-width: 1pt; background-color: rgb(217, 217, 217); padding: 0cm 5.4pt; background-position: initial initial; background-repeat: initial initial;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">-fast-isel=default<o:p class=""></o:p></span></div></td><td width="121" valign="top" style="width: 90.85pt; border-style: solid solid solid none; border-top-color: windowtext; border-right-color: windowtext; border-bottom-color: windowtext; border-top-width: 1pt; border-right-width: 1pt; border-bottom-width: 1pt; background-color: rgb(217, 217, 217); padding: 0cm 5.4pt; background-position: initial initial; background-repeat: initial initial;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">-fast-isel=true<o:p class=""></o:p></span></div></td></tr><tr class=""><td width="161" valign="top" style="width: 120.5pt; border-style: none solid solid; border-right-color: windowtext; border-bottom-color: windowtext; border-left-color: windowtext; border-right-width: 1pt; border-bottom-width: 1pt; border-left-width: 1pt; background-color: rgb(217, 217, 217); padding: 0cm 5.4pt; background-position: initial initial; background-repeat: initial initial;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">-O0<o:p class=""></o:p></span></div></td><td width="131" valign="top" style="width: 98.55pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">SelectionDAG<o:p class=""></o:p></span></div></td><td width="122" valign="top" style="width: 91.8pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">FastISel<o:p class=""></o:p></span></div></td><td width="121" valign="top" style="width: 90.85pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">FastISel<o:p class=""></o:p></span></div></td></tr><tr class=""><td width="161" valign="top" style="width: 120.5pt; border-style: none solid solid; border-right-color: windowtext; border-bottom-color: windowtext; border-left-color: windowtext; border-right-width: 1pt; border-bottom-width: 1pt; border-left-width: 1pt; background-color: rgb(217, 217, 217); padding: 0cm 5.4pt; background-position: initial initial; background-repeat: initial initial;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">-O0 + optnone attribute<o:p class=""></o:p></span></div></td><td width="131" valign="top" style="width: 98.55pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">SelectionDAG*<o:p class=""></o:p></span></div></td><td width="122" valign="top" style="width: 91.8pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">FastISel<o:p class=""></o:p></span></div></td><td width="121" valign="top" style="width: 90.85pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">FastISel<o:p class=""></o:p></span></div></td></tr><tr class=""><td width="161" valign="top" style="width: 120.5pt; border-style: none solid solid; border-right-color: windowtext; border-bottom-color: windowtext; border-left-color: windowtext; border-right-width: 1pt; border-bottom-width: 1pt; border-left-width: 1pt; background-color: rgb(217, 217, 217); padding: 0cm 5.4pt; background-position: initial initial; background-repeat: initial initial;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">-O1 + optnone attribute<o:p class=""></o:p></span></div></td><td width="131" valign="top" style="width: 98.55pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">SelectionDAG*<o:p class=""></o:p></span></div></td><td width="122" valign="top" style="width: 91.8pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">FastISel<o:p class=""></o:p></span></div></td><td width="121" valign="top" style="width: 90.85pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">FastISel<o:p class=""></o:p></span></div></td></tr><tr class=""><td width="161" valign="top" style="width: 120.5pt; border-style: none solid solid; border-right-color: windowtext; border-bottom-color: windowtext; border-left-color: windowtext; border-right-width: 1pt; border-bottom-width: 1pt; border-left-width: 1pt; background-color: rgb(217, 217, 217); padding: 0cm 5.4pt; background-position: initial initial; background-repeat: initial initial;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">-O2 + optnone attribute<o:p class=""></o:p></span></div></td><td width="131" valign="top" style="width: 98.55pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">SelectionDAG*<o:p class=""></o:p></span></div></td><td width="122" valign="top" style="width: 91.8pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">FastISel<o:p class=""></o:p></span></div></td><td width="121" valign="top" style="width: 90.85pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">FastISel<o:p class=""></o:p></span></div></td></tr><tr class=""><td width="161" valign="top" style="width: 120.5pt; border-style: none solid solid; border-right-color: windowtext; border-bottom-color: windowtext; border-left-color: windowtext; border-right-width: 1pt; border-bottom-width: 1pt; border-left-width: 1pt; background-color: rgb(217, 217, 217); padding: 0cm 5.4pt; background-position: initial initial; background-repeat: initial initial;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">-O3 + optnone attribute<o:p class=""></o:p></span></div></td><td width="131" valign="top" style="width: 98.55pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">SelectionDAG*<o:p class=""></o:p></span></div></td><td width="122" valign="top" style="width: 91.8pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">FastISel<o:p class=""></o:p></span></div></td><td width="121" valign="top" style="width: 90.85pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">FastISel<o:p class=""></o:p></span></div></td></tr><tr class=""><td width="161" valign="top" style="width: 120.5pt; border-style: none solid solid; border-right-color: windowtext; border-bottom-color: windowtext; border-left-color: windowtext; border-right-width: 1pt; border-bottom-width: 1pt; border-left-width: 1pt; background-color: rgb(217, 217, 217); padding: 0cm 5.4pt; background-position: initial initial; background-repeat: initial initial;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">-O1<o:p class=""></o:p></span></div></td><td width="131" valign="top" style="width: 98.55pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">SelectionDAG<o:p class=""></o:p></span></div></td><td width="122" valign="top" style="width: 91.8pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">SelectionDAG<o:p class=""></o:p></span></div></td><td width="121" valign="top" style="width: 90.85pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">FastISel<o:p class=""></o:p></span></div></td></tr><tr class=""><td width="161" valign="top" style="width: 120.5pt; border-style: none solid solid; border-right-color: windowtext; border-bottom-color: windowtext; border-left-color: windowtext; border-right-width: 1pt; border-bottom-width: 1pt; border-left-width: 1pt; background-color: rgb(217, 217, 217); padding: 0cm 5.4pt; background-position: initial initial; background-repeat: initial initial;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">-O2<o:p class=""></o:p></span></div></td><td width="131" valign="top" style="width: 98.55pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">SelectionDAG<o:p class=""></o:p></span></div></td><td width="122" valign="top" style="width: 91.8pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">SelectionDAG<o:p class=""></o:p></span></div></td><td width="121" valign="top" style="width: 90.85pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">FastISel<o:p class=""></o:p></span></div></td></tr><tr class=""><td width="161" valign="top" style="width: 120.5pt; border-style: none solid solid; border-right-color: windowtext; border-bottom-color: windowtext; border-left-color: windowtext; border-right-width: 1pt; border-bottom-width: 1pt; border-left-width: 1pt; background-color: rgb(217, 217, 217); padding: 0cm 5.4pt; background-position: initial initial; background-repeat: initial initial;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">-O3<o:p class=""></o:p></span></div></td><td width="131" valign="top" style="width: 98.55pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">SelectionDAG<o:p class=""></o:p></span></div></td><td width="122" valign="top" style="width: 91.8pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">SelectionDAG<o:p class=""></o:p></span></div></td><td width="121" valign="top" style="width: 90.85pt; border-style: none solid solid none; border-bottom-color: windowtext; border-bottom-width: 1pt; border-right-color: windowtext; border-right-width: 1pt; padding: 0cm 5.4pt;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">FastISel<o:p class=""></o:p></span></div></td></tr></tbody></table><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">The cells marked with '*' differ from the current behavior.</span></div></div></div></blockquote>This table is excellent. Any chance you can find a good place in code to put it, or even somewhere in the docs?</div><div><br class=""></div><div>I did look to see if <a href="http://llvm.org/docs/WritingAnLLVMBackend.html#instruction-selector" class="">http://llvm.org/docs/WritingAnLLVMBackend.html#instruction-selector</a> had a section on fast-isel but it surprisingly doesn’t. If it did, I think this table would have been good to put there to explain when a backend will get which selector.</div><div><br class=""></div><div>Cheers,</div><div>Pete<br class=""><blockquote type="cite" class=""><div class=""><div class="WordSection1" style="page: WordSection1; font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class=""><o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-family: 'Courier New';" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">In terms of code, I think this part of OptLevelChanger::OptLevelChanger():<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-family: 'Courier New';" class=""> if (NewOptLevel == CodeGenOpt::None) {<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-family: 'Courier New';" class=""> DEBUG(dbgs() << "\nEnable FastISel for Function "<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-family: 'Courier New';" class=""> << IS.MF->getFunction()->getName() << "\n");<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-family: 'Courier New';" class=""> IS.TM.setFastISel(true);<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-family: 'Courier New';" class=""> }<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">Should be:<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-family: 'Courier New';" class=""> if (NewOptLevel == CodeGenOpt::None) {<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-family: 'Courier New';" class=""> DEBUG(dbgs() << "\nEnable FastISel for Function "<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-family: 'Courier New';" class=""> << IS.MF->getFunction()->getName() << "\n");<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-family: 'Courier New';" class=""> IS.TM.setFastISel(EnableFastISelOption != cl::BOU_FALSE);<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-family: 'Courier New';" class=""> }<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">Where EnableFastISelOption has the same value as the global in LLVMTargetMachine.cpp<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">The main reason I'm asking for this is that I think it's weird to for optnone to use a different code generator<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">than –O0. These hidden overrides exist to help us debug code generation problems and, faced with a code<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">generation bug, –fast-isel=false is useful for quickly determining whether it's in FastISel or somewhere else.<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">The current behaviour allows optnone to overrule the hidden option to force-disable FastISel which will give<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="" class="">misleading guidance for bugs that lie in functions with optnone.<o:p class=""></o:p></span></div></div><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">_______________________________________________</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">LLVM Developers mailing list</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><a href="mailto:llvm-dev@lists.llvm.org" style="color: purple; text-decoration: underline; font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">llvm-dev@lists.llvm.org</a><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><a href="http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev" style="color: purple; text-decoration: underline; font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a></div></blockquote></div><br class=""></div></body></html>