Add an index for Module Metadata record in the bitcode

Summary:
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.

Reviewers: pcc, tejohnson

Subscribers: llvm-commits

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

llvm-svn: 290684

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/test/Bitcode/mdnodes-in-post-order.ll b/llvm/test/Bitcode/mdnodes-in-post-order.ll
index fbe1c34cf00..845175d6879 100644
--- a/llvm/test/Bitcode/mdnodes-in-post-order.ll
+++ b/llvm/test/Bitcode/mdnodes-in-post-order.ll
@@ -15,6 +15,9 @@
 ; CHECK-NEXT:    'leaf
 ; CHECK-NEXT:  }
 
+; Before the records we emit an offset to the index for the block
+; CHECK-NEXT:   <INDEX_OFFSET
+
 ; The leafs should come first (in either order).
 ; CHECK-NEXT:  <NODE op0=1/>
 ; CHECK-NEXT:  <NODE op0=2/>
@@ -27,6 +30,10 @@
 ; CHECK-NEXT:  <NODE op0=3 op1=5 op2=4/>
 !6 = !{!3, !5, !4}
 
+; Before the named records we emit the index containing the position of the
+; previously emitted records
+; CHECK-NEXT:   <INDEX {{.*}} (offset match)
+
 ; Note: named metadata nodes are not cannot reference null so their operands
 ; are numbered off-by-one.
 ; CHECK-NEXT:  <NAME