[PATCH] D19481: [ThinLTO] Use valueid instead of bitcode offsets in combined index file

[Teresa Johnson via llvm-commits]

tejohnson created this revision.
tejohnson added a reviewer: joker.eph.
tejohnson added a subscriber: llvm-commits.
Herald added a subscriber: joker.eph.

With the removal of support for lazy parsing of combined index summary
records (e.g. r267344), we no longer need to include the summary record
bitcode offset in the VST entries for definitions. Change the combined
index format to be similar to the per-module index format in using value
ids to cross-reference from the summary record to the VST entry (rather
than the summary record bitcode offset to cross-reference in the other
direction).

The visible changes are:
1) Add the value id to the combined summary records
2) Remove the summary offset from the combined VST records, which has
the following effects:
- No longer need the VST_CODE_COMBINED_GVDEFENTRY record, as all
  combined index VST entries now only contain the value id and
  corresponding GUID.
- No longer have duplicate VST entries in the case where there are
  multiple definitions of a symbol (e.g. weak/linkonce), as they all
  have the same value id and GUID.

An implication of #2 above is that in order to hook up an alias to the
correct aliasee based on the value id of the aliasee recorded in the
combined index alias record, we need to scan the entries in the index
for that GUID to find the one from the same module (i.e. the case where
there are multiple entries for the aliasee). But the reader no longer
has to maintain a special map to hook up the alias/aliasee.

http://reviews.llvm.org/D19481

Files:
  include/llvm/Bitcode/LLVMBitCodes.h
  lib/Bitcode/Reader/BitcodeReader.cpp
  lib/Bitcode/Writer/BitcodeWriter.cpp
  test/Bitcode/thinlto-alias.ll
  test/Bitcode/thinlto-function-summary-callgraph-pgo.ll
  test/Bitcode/thinlto-function-summary-callgraph.ll
  test/Bitcode/thinlto-function-summary-originalnames.ll
  test/Bitcode/thinlto-summary-linkage-types.ll
  test/Bitcode/thinlto-summary-section.ll
  test/tools/gold/X86/thinlto.ll
  test/tools/llvm-lto/thinlto.ll
  tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp

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