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<p class="MsoNormal">Currently, the <span style="font-size:10.0pt;font-family:Consolas">
alloca</span> instruction always allocates in the generic address space (0).<o:p></o:p></p>
<p class="MsoNormal">This proposal is to extend the semantics of <span style="font-size:10.0pt;font-family:Consolas">
alloca</span> instruction to allow allocation in any specified address space.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b>Proposed Syntax<o:p></o:p></b></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:Consolas"><result> = alloca [inalloca] <type> [, <ty> <NumElements>] [, align <alignment>]
<b>[, <span style="color:black;background:white">addrspace </span><<span style="color:black;background:white">num</span>>]</b> ; yields type addrspace(num)*:result<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:Consolas"><o:p> </o:p></span></p>
<p class="MsoNormal"><b>Motivation<o:p></o:p></b></p>
<p class="MsoNormal">Managed language clients typically use address space 1 to represent GC-pointers.<o:p></o:p></p>
<p class="MsoNormal">Some managed clients (CLR, in particular) allow construction of GC pointers to stack locations.<o:p></o:p></p>
<p class="MsoNormal">For example, MSIL instruction ldloca (ECMA 335, p 370) creates a GC pointer to a stack local.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Creating an <span style="font-size:10.0pt;font-family:Consolas">
addrespace(1)*</span> pointer to a stack location currently involves two steps: the
<span style="font-size:10.0pt;font-family:Consolas">alloca</span>, and an <span style="font-size:10.0pt;font-family:Consolas">
addrspacecast</span>.<o:p></o:p></p>
<p class="MsoNormal">Managed code transformations (ex: <span style="font-size:10.0pt;font-family:Consolas">
RewriteStatepointsForGC</span>) do not handle arbitrary address space casting.<o:p></o:p></p>
<p class="MsoNormal">So, it is desirable to obtain the <span style="font-size:10.0pt;font-family:Consolas">
addrespace(1)*</span> pointer by construction.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks,<o:p></o:p></p>
<p class="MsoNormal">Swaroop.<o:p></o:p></p>
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