xref: /llvm-project/llvm/test/Bitcode/mdnodes-distinct-nodes-break-cycles.ll (revision e98f9258349aeb8414a556326aeee8ba94a7c839)
1*e98f9258SMehdi Amini; RUN: llvm-as <%s -bitcode-mdindex-threshold=0 | llvm-bcanalyzer -dump | FileCheck %s
230805b24SDuncan P. N. Exon Smith; Check that distinct nodes break uniquing cycles, so that uniqued subgraphs
330805b24SDuncan P. N. Exon Smith; are always in post-order.
430805b24SDuncan P. N. Exon Smith;
530805b24SDuncan P. N. Exon Smith; It may not be immediately obvious why this is an interesting graph.  There
630805b24SDuncan P. N. Exon Smith; are three nodes in a cycle, and one of them (!1) is distinct.  Because the
730805b24SDuncan P. N. Exon Smith; entry point is !2, a naive post-order traversal would give !3, !1, !2; but
830805b24SDuncan P. N. Exon Smith; this means when !3 is parsed the reader will need a forward reference for !2.
930805b24SDuncan P. N. Exon Smith; Forward references for uniqued node operands are expensive, whereas they're
1030805b24SDuncan P. N. Exon Smith; cheap for distinct node operands.  If the distinct node is emitted first, the
1130805b24SDuncan P. N. Exon Smith; uniqued nodes don't need any forward references at all.
1230805b24SDuncan P. N. Exon Smith
1330805b24SDuncan P. N. Exon Smith; Nodes in this testcase are numbered to match how they are referenced in
1430805b24SDuncan P. N. Exon Smith; bitcode.  !3 is referenced as opN=3.
1530805b24SDuncan P. N. Exon Smith
1630805b24SDuncan P. N. Exon Smith; CHECK:       <DISTINCT_NODE op0=3/>
1730805b24SDuncan P. N. Exon Smith!1 = distinct !{!3}
1830805b24SDuncan P. N. Exon Smith
1930805b24SDuncan P. N. Exon Smith; CHECK-NEXT:  <NODE op0=1/>
2030805b24SDuncan P. N. Exon Smith!2 = !{!1}
2130805b24SDuncan P. N. Exon Smith
2230805b24SDuncan P. N. Exon Smith; CHECK-NEXT:  <NODE op0=2/>
2330805b24SDuncan P. N. Exon Smith!3 = !{!2}
2430805b24SDuncan P. N. Exon Smith
25*e98f9258SMehdi Amini; Before the named records we emit the index containing the position of the
26*e98f9258SMehdi Amini; previously emitted records
27*e98f9258SMehdi Amini; CHECK-NEXT:   <INDEX {{.*}} (offset match)
28*e98f9258SMehdi Amini
2930805b24SDuncan P. N. Exon Smith; Note: named metadata nodes are not cannot reference null so their operands
3030805b24SDuncan P. N. Exon Smith; are numbered off-by-one.
3130805b24SDuncan P. N. Exon Smith; CHECK-NEXT:  <NAME
3230805b24SDuncan P. N. Exon Smith; CHECK-NEXT:  <NAMED_NODE op0=1/>
3330805b24SDuncan P. N. Exon Smith!named = !{!2}
34