forked from OSchip/llvm-project
30 lines
1.1 KiB
LLVM
30 lines
1.1 KiB
LLVM
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; RUN: llvm-as <%s | llvm-bcanalyzer -dump | FileCheck %s
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; Check that distinct nodes break uniquing cycles, so that uniqued subgraphs
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; are always in post-order.
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;
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; It may not be immediately obvious why this is an interesting graph. There
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; are three nodes in a cycle, and one of them (!1) is distinct. Because the
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; entry point is !2, a naive post-order traversal would give !3, !1, !2; but
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; this means when !3 is parsed the reader will need a forward reference for !2.
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; Forward references for uniqued node operands are expensive, whereas they're
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; cheap for distinct node operands. If the distinct node is emitted first, the
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; uniqued nodes don't need any forward references at all.
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; Nodes in this testcase are numbered to match how they are referenced in
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; bitcode. !3 is referenced as opN=3.
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; CHECK: <DISTINCT_NODE op0=3/>
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!1 = distinct !{!3}
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; CHECK-NEXT: <NODE op0=1/>
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!2 = !{!1}
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; CHECK-NEXT: <NODE op0=2/>
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!3 = !{!2}
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; Note: named metadata nodes are not cannot reference null so their operands
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; are numbered off-by-one.
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; CHECK-NEXT: <NAME
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; CHECK-NEXT: <NAMED_NODE op0=1/>
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!named = !{!2}
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