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llvm-mirror/test/Bitcode/mdnodes-distinct-nodes-first.ll
Duncan P. N. Exon Smith f5921278f9 BitcodeWriter: Emit distinct nodes before uniqued nodes
When an operand of a distinct node hasn't been read yet, the reader can
use a DistinctMDOperandPlaceholder.  This is much cheaper than forward
referencing from a uniqued node.  Change
ValueEnumerator::organizeMetadata to partition distinct nodes and
uniqued nodes to reduce the overhead of cycles broken by distinct nodes.

Mehdi measured this for me; this removes most of the RAUW from the
importing step of -flto=thin, even after a WIP patch that removes
string-based DITypeRefs (introducing many more cycles to the metadata
graph).

llvm-svn: 267276
2016-04-23 04:42:39 +00:00

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LLVM

; RUN: llvm-as <%s | llvm-bcanalyzer -dump | FileCheck %s
; Check that distinct nodes are emitted before uniqued nodes, even if that
; breaks post-order traversals.
; Nodes in this testcase are numbered to match how they are referenced in
; bitcode. !1 is referenced as opN=1.
; CHECK: <DISTINCT_NODE op0=2/>
!1 = distinct !{!2}
; CHECK-NEXT: <NODE op0=1/>
!2 = !{!1}
; Note: named metadata nodes are not cannot reference null so their operands
; are numbered off-by-one.
; CHECK-NEXT: <NAME
; CHECK-NEXT: <NAMED_NODE op0=1/>
!named = !{!2}