From d248f027955c6d032adfe9b65e41ef0fe5322eb4 Mon Sep 17 00:00:00 2001
From: Zachary Turner <zturner@google.com>
Date: Fri, 5 Apr 2019 17:12:37 +0000
Subject: [PDB Docs] Add info about the hash adjustment buffer.

This necessitates adding a document describing the serialized
hash table format.  This document is currently empty, although
it will be filled out in followup patches.

llvm-svn: 357784
---
 llvm/docs/PDB/HashStream.rst |  3 ---
 llvm/docs/PDB/HashTable.rst  |  2 ++
 llvm/docs/PDB/TpiStream.rst  | 10 +++++++++-
 llvm/docs/PDB/index.rst      |  8 ++++----
 4 files changed, 15 insertions(+), 8 deletions(-)
 delete mode 100644 llvm/docs/PDB/HashStream.rst
 create mode 100644 llvm/docs/PDB/HashTable.rst

(limited to 'llvm/docs/PDB')

diff --git a/llvm/docs/PDB/HashStream.rst b/llvm/docs/PDB/HashStream.rst
deleted file mode 100644
index a758db4d03d..00000000000
--- a/llvm/docs/PDB/HashStream.rst
+++ /dev/null
@@ -1,3 +0,0 @@
-=====================================
-The TPI & IPI Hash Streams
-=====================================
diff --git a/llvm/docs/PDB/HashTable.rst b/llvm/docs/PDB/HashTable.rst
new file mode 100644
index 00000000000..fbf4a1de528
--- /dev/null
+++ b/llvm/docs/PDB/HashTable.rst
@@ -0,0 +1,2 @@
+The PDB Serialized Hash Table Format
+====================================
diff --git a/llvm/docs/PDB/TpiStream.rst b/llvm/docs/PDB/TpiStream.rst
index 74f2c37b083..99f9a73bb11 100644
--- a/llvm/docs/PDB/TpiStream.rst
+++ b/llvm/docs/PDB/TpiStream.rst
@@ -289,7 +289,15 @@ accurate.
   index.  This can be used to do a binary search followed bin a linear search to
   get amortized O(log n) lookup by type index.
 
-- **HashAdjBufferOffset / HashAdjBufferLength** - 
+- **HashAdjBufferOffset / HashAdjBufferLength** - The offset and size within
+  the TPI hash stream of a serialized hash table whose keys are the hash values
+  in the hash value buffer and whose values are type indices.  This appears to
+  be useful in incremental linking scenarios, so that if a type is modified an
+  entry can be created mapping the old hash value to the new type index so that
+  a PDB file consumer can always have the most up to date version of the type
+  without forcing the incremental linker to garbage collect and update
+  references that point to the old version to now point to the new version.
+  The layout of this hash table is described in :doc:`HashTable`.
 
 .. _tpi_records:
 
diff --git a/llvm/docs/PDB/index.rst b/llvm/docs/PDB/index.rst
index d1b4379dbf8..a6054d720bd 100644
--- a/llvm/docs/PDB/index.rst
+++ b/llvm/docs/PDB/index.rst
@@ -52,7 +52,7 @@ File Layout
    ModiStream
    PublicStream
    GlobalStream
-   HashStream
+   HashTable
    CodeViewSymbols
    CodeViewTypes
 
@@ -158,9 +158,9 @@ following pages:
 :doc:`GlobalStream`
    Information about the Global Symbol Stream.
 
-:doc:`HashStream`
-   Information about the Hash Table stream, and how it can be used to quickly look up records
-   by name.
+:doc:`HashTable`
+   Information about the serialized hash table format used internally to represent things such
+   as the Named Stream Map and the Hash Adjusters in the :doc:`TPI/IPI Stream <TpiStream>`.
 
 CodeView
 ========
-- 
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