llvm-mirror/test/Bitcode/mdnodes-distinct-in-post-order.ll
Mehdi Amini 57004ae3ac Add an index for Module Metadata record in the bitcode
This index record the position for each metadata record in
the bitcode, so that the reader will be able to lazy-load
on demand each individual record.

We also make sure that every abbrev is emitted upfront so
that the block can be skipped while reading.

I don't plan to commit this before having the reader
counterpart, but I figured this can be reviewed mostly
independently.

Recommit r290684 (was reverted in r290686 because a test
was broken) after adding a threshold to avoid emitting
the index when unnecessary (little amount of metadata).
This optimization "hides" a limitation of the ability
to backpatch in the bitstream: we can only backpatch
safely when the position has been flushed. So if we emit
an index for one metadata, it is possible that (part of)
the offset placeholder hasn't been flushed and the backpatch
will fail.

Differential Revision: https://reviews.llvm.org/D28083

llvm-svn: 290690
2016-12-28 22:30:28 +00:00

31 lines
1.1 KiB
LLVM

; RUN: llvm-as <%s -bitcode-mdindex-threshold=0 | llvm-bcanalyzer -dump | FileCheck %s -check-prefix=CHECK -check-prefix=MDINDEX
; RUN: llvm-as <%s | llvm-bcanalyzer -dump | FileCheck %s -check-prefix=CHECK
; Check that distinct nodes are emitted in post-order to avoid unnecessary
; forward references.
; Nodes in this testcase are numbered to match how they are referenced in
; bitcode. !3 is referenced as opN=3.
; The leafs should come first (in either order).
; CHECK: <DISTINCT_NODE/>
; CHECK-NEXT: <DISTINCT_NODE/>
!1 = distinct !{}
!2 = distinct !{}
; CHECK-NEXT: <DISTINCT_NODE op0=1 op1=2/>
!3 = distinct !{!1, !2}
; CHECK-NEXT: <DISTINCT_NODE op0=1 op1=3 op2=2/>
!4 = distinct !{!1, !3, !2}
; Before the named records we emit the index containing the position of the
; previously emitted records, but only if we have a number of record above
; a threshold (can be controlled through `-bitcode-mdindex-threshold`).
; MDINDEX: <INDEX {{.*}} (offset match)
; 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=3/>
!named = !{!4}