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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - TargetLowering::computeKnownBitsForTargetNode - constant pool extraction"
href="https://bugs.llvm.org/show_bug.cgi?id=45315">45315</a>
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<th>Summary</th>
<td>TargetLowering::computeKnownBitsForTargetNode - constant pool extraction
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<th>Product</th>
<td>libraries
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<th>Version</th>
<td>trunk
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>Windows NT
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Common Code Generator Code
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>llvm-dev@redking.me.uk
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<th>CC</th>
<td>craig.topper@gmail.com, efriedma@quicinc.com, llvm-bugs@lists.llvm.org, spatel+llvm@rotateright.com
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<pre>We can't safely extract the knownbits of target constant pools (e.g.
X86ISD::VBROADCAST_LOAD) because SimplifyDemandedBits may then attempt to
constant fold it, which then infinite loops as it gets relowered to
X86ISD::VBROADCAST_LOAD again......
As an initial stopgap, we could just not constant fold if SimplifyDemandedBits
encounters an opcode above FIRST_TARGET_MEMORY_OPCODE (or is a MemSDNode?) but
this doesn't address non-loading target patterns that might be used for
constant creation, so maybe we need some way to flag that a
computeKnownBitsForTargetNode call came from a lowered constant?</pre>
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