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    <div class="moz-cite-prefix">On 3/25/20 12:25 PM, Florian Hahn via
      llvm-dev wrote:<br>
    </div>
    <blockquote type="cite"
      cite="mid:F463FA86-CC7F-4314-B6AA-8301E2A0CEAD@apple.com">
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        <blockquote type="cite" class="">
          <div class="">On Mar 25, 2020, at 15:35, Nicolai Hähnle via
            llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org"
              class="" moz-do-not-send="true">llvm-dev@lists.llvm.org</a>>
            wrote:</div>
          <br class="Apple-interchange-newline">
          <div class=""><span style="caret-color: rgb(0, 0, 0);
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              !important;" class="">On Wed, Mar 25, 2020 at 8:52 AM
              Doerfert, Johannes <</span><a
              href="mailto:jdoerfert@anl.gov" style="font-family:
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              0px;" class="" moz-do-not-send="true">jdoerfert@anl.gov</a><span
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
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              float: none; display: inline !important;" class="">>
              wrote:</span><br style="caret-color: rgb(0, 0, 0);
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            <blockquote type="cite" style="font-family: Helvetica;
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              class="">I think the solution space for the value/use-list
              issue might be larger<br class="">
              than what was mentioned so far.<br class="">
              <br class="">
              <br class="">
              Some random thoughts:<br class="">
              <br class="">
              If no pass ever walks the use list of a constant, except
              globals which<br class="">
              we could handle differently, we could get rid of their
              use-list or<br class="">
              overwrite their use-list interface functions to make them
              no-ops. We<br class="">
              could also do this kind of specialization in the Use class
              (I think).<br class="">
            </blockquote>
            <br style="caret-color: rgb(0, 0, 0); font-family:
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              text-decoration: none;" class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
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              !important;" class="">Okay, let's actually think through
              how practical that is. The class</span><br
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              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">hierarchy is:</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
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              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <br style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none;" class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">Value</span><br style="caret-color:
              rgb(0, 0, 0); font-family: Helvetica; font-size: 12px;
              font-style: normal; font-variant-caps: normal;
              font-weight: normal; letter-spacing: normal; text-align:
              start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">- Argument</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">- BasicBlock</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">- InlineAsm (huh, why is that not a
              constant?)</span><br style="caret-color: rgb(0, 0, 0);
              font-family: Helvetica; font-size: 12px; font-style:
              normal; font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none;" class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">- MetadataAsValue (+ children)</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">- User</span><br style="caret-color:
              rgb(0, 0, 0); font-family: Helvetica; font-size: 12px;
              font-style: normal; font-variant-caps: normal;
              font-weight: normal; letter-spacing: normal; text-align:
              start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">-- Instruction (+ children)</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">-- Constant</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">--- ConstantData (undef, token none,
              literals)</span><br style="caret-color: rgb(0, 0, 0);
              font-family: Helvetica; font-size: 12px; font-style:
              normal; font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none;" class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">--- ConstantAggregate (non-literal
              aggregates)</span><br style="caret-color: rgb(0, 0, 0);
              font-family: Helvetica; font-size: 12px; font-style:
              normal; font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none;" class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">--- BlockAddress</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">--- ConstantExpr</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">--- GlobalValue (+ children)</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">-- Operator (utility / facade, i.e.
              not real)</span><br style="caret-color: rgb(0, 0, 0);
              font-family: Helvetica; font-size: 12px; font-style:
              normal; font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none;" class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">-- DerivedUser (extension point used
              by MemorySSA)</span><br style="caret-color: rgb(0, 0, 0);
              font-family: Helvetica; font-size: 12px; font-style:
              normal; font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none;" class="">
            <br style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none;" class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">It seems to me that the only points
              of this hierarchy that are</span><br style="caret-color:
              rgb(0, 0, 0); font-family: Helvetica; font-size: 12px;
              font-style: normal; font-variant-caps: normal;
              font-weight: normal; letter-spacing: normal; text-align:
              start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">guaranteed to be function-local are
              Argument and Instruction.</span><br style="caret-color:
              rgb(0, 0, 0); font-family: Helvetica; font-size: 12px;
              font-style: normal; font-variant-caps: normal;
              font-weight: normal; letter-spacing: normal; text-align:
              start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">Everything else could end up having
              uses from multiple functions</span><br style="caret-color:
              rgb(0, 0, 0); font-family: Helvetica; font-size: 12px;
              font-style: normal; font-variant-caps: normal;
              font-weight: normal; letter-spacing: normal; text-align:
              start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">and/or initializers of globals.
              DerivedUser seems particularly special</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">-- but it's only used by MemorySSA,
              and that appears to be</span><br style="caret-color:
              rgb(0, 0, 0); font-family: Helvetica; font-size: 12px;
              font-style: normal; font-variant-caps: normal;
              font-weight: normal; letter-spacing: normal; text-align:
              start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">function-local?</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <br style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none;" class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">Of the values that can have global
              references to them, I believe that</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">most could just be immortal and
              without use lists. I'd say this</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">applies to:</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">- InlineAsm</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">- MetadataAsValue</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">- Constant other than GlobalValue</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <br style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none;" class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">This leaves as values with global
              references that _cannot_ be immortal:</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">- GlobalValue (+ children)</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">- BasicBlock</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <br style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none;" class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">And values that will have use lists,
              and only local references are:</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">- Argument</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">- Instruction</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <br style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none;" class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">So the following does seem like a
              feasible minimal step forward:</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <br style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none;" class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">1. Build a mechanism to break the
              use dependencies for GlobalValue and</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">BasicBlock, i.e. allow immortal
              BlockAddress and ConstantGlobalValue</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">values while _also_ allowing us to
              delete GlobalValues and</span><br style="caret-color:
              rgb(0, 0, 0); font-family: Helvetica; font-size: 12px;
              font-style: normal; font-variant-caps: normal;
              font-weight: normal; letter-spacing: normal; text-align:
              start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">BasicBlocks.</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <br style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none;" class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">For this mechanism, we can let
              ourselves be inspired by</span><br style="caret-color:
              rgb(0, 0, 0); font-family: Helvetica; font-size: 12px;
              font-style: normal; font-variant-caps: normal;
              font-weight: normal; letter-spacing: normal; text-align:
              start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">mlir::SymbolRefAttr, which uses
              strings for the linkage.</span><br style="caret-color:
              rgb(0, 0, 0); font-family: Helvetica; font-size: 12px;
              font-style: normal; font-variant-caps: normal;
              font-weight: normal; letter-spacing: normal; text-align:
              start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <br style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none;" class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">Alternatively (and perhaps
              preferably), we could use a weak_ptr-like</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">mechanism. This can be very
              efficient, since each GlobalValue and</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">BasicBlock only ever needs to have a
              single instance of</span><br style="caret-color: rgb(0, 0,
              0); font-family: Helvetica; font-size: 12px; font-style:
              normal; font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none;" class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">ConstantGlobalValue and BlockAddress
              referring to it, respectively, so</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">a simple back-link is sufficient.</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <br style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none;" class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">2. Change setOperand to only update
              use lists of Argument and</span><br style="caret-color:
              rgb(0, 0, 0); font-family: Helvetica; font-size: 12px;
              font-style: normal; font-variant-caps: normal;
              font-weight: normal; letter-spacing: normal; text-align:
              start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">Instruction. All other use lists
              will always be empty -- no special</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">handling in the use list accessors
              is required, but we should place</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">assertions there to assert that use
              lists are not accidentally used on</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">other value types.</span><br
              style="caret-color: rgb(0, 0, 0); font-family: Helvetica;
              font-size: 12px; font-style: normal; font-variant-caps:
              normal; font-weight: normal; letter-spacing: normal;
              text-align: start; text-indent: 0px; text-transform: none;
              white-space: normal; word-spacing: 0px;
              -webkit-text-stroke-width: 0px; text-decoration: none;"
              class="">
            <br style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none;" class="">
            <span style="caret-color: rgb(0, 0, 0); font-family:
              Helvetica; font-size: 12px; font-style: normal;
              font-variant-caps: normal; font-weight: normal;
              letter-spacing: normal; text-align: start; text-indent:
              0px; text-transform: none; white-space: normal;
              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              text-decoration: none; float: none; display: inline
              !important;" class="">How does that sound for that start?</span></div>
        </blockquote>
        <br class="">
      </div>
      <div>I think one important observation is that most passes
        currently probably do not really care too much about use lists
        of various constants, beyond the bookkeeping required to
        maintain them.</div>
      <div><br class="">
      </div>
      <div>We might be able to break the dependencies on GlobalValue
        without too much work directly as an IR transformation. I’ve not
        thought this completely through, but we might get away with a
        module pass that duplicate globals per function and replace all
        uses in a function with the copy per function before running a
        set of function passes. Then merge the duplicates again before
        running passes that inspect global uses. It is probably not an
        optimal solution, but it might shorten the path towards getting
        into a state where we can run function passes in parallel. It
        would also require making ConstantInt & co function-local,
        but both things could be implemented in parallel.</div>
      <div><br class="">
      </div>
      <div>I think this thread explores the problem in quite a few
        directions very well. It might be worth summarizing the problems
        & possible solutions somewhere, e.g. the docs, to preserve
        them.</div>
      <div><br class="">
      </div>
      <div>Cheers,</div>
      <div>Florian</div>
      <br>
    </blockquote>
    I don't have access to the wiki for writing but I'm taking notes on
    what should  be added as I read the thread. :) Probably the holy
    grail<br>
    for multi threading a compiler is to make the pass manager async. I
    tried for months on the GCC side to figure that out by reading<br>
    the code e.t.c., its almost impossible it seems without IR level
    state detection.<br>
    <br>
    Frankly I gave up on that but if people are curious its a issue of
    IPO between passes and pass reordering issues,<br>
    <br>
    Nick<br>
    <blockquote type="cite"
      cite="mid:F463FA86-CC7F-4314-B6AA-8301E2A0CEAD@apple.com">
      <fieldset class="mimeAttachmentHeader"></fieldset>
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    </blockquote>
    <br>
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