Commit Graph

3 Commits

Author SHA1 Message Date
Teresa Johnson e1164de5d0 Restore "[ThinLTO] Use MD5 hash in function index." with fix
This restores commit r260408, along with a fix for a bot failure.

The bot failure was caused by dereferencing a unique_ptr in the same
call instruction parameter list where it was passed via std::move.
Apparently due to luck this was not exposed when I built the compiler
with clang, only with gcc.

llvm-svn: 260442
2016-02-10 21:55:02 +00:00
Teresa Johnson 89f38fb5cc Revert "[ThinLTO] Use MD5 hash in function index." due to bot failure
This reverts commit r260408. Bot failure that I need to investigate.

llvm-svn: 260412
2016-02-10 19:11:15 +00:00
Teresa Johnson 0919a84071 [ThinLTO] Use MD5 hash in function index.
Summary:
This patch uses the lower 64-bits of the MD5 hash of a function name as
a GUID in the function index, instead of storing function names. Any
local functions are first given a global name by prepending the original
source file name. This is the same naming scheme and GUID used by PGO in
the indexed profile format.

This change has a couple of benefits. The primary benefit is size
reduction in the combined index file, for example 483.xalancbmk's
combined index file was reduced by around 70%. It should also result in
memory savings for the index file in memory, as the in-memory map is
also indexed by the hash instead of the string.

Second, this enables integration with indirect call promotion, since the
indirect call profile targets are recorded using the same global naming
convention and hash. This will enable the function importer to easily
locate function summaries for indirect call profile targets to enable
their import and subsequent promotion.

The original source file name is recorded in the bitcode in a new
module-level record for use in the ThinLTO backend pipeline.

Reviewers: davidxl, joker.eph

Subscribers: llvm-commits, joker.eph

Differential Revision: http://reviews.llvm.org/D17028

llvm-svn: 260408
2016-02-10 18:57:54 +00:00