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Summary:
Records in the module summary index whether the bitcode was compiled
with the option necessary to enable splitting the LTO unit
(e.g. -fsanitize=cfi, -fwhole-program-vtables, or -fsplit-lto-unit).
The information is passed down to the ModuleSummaryIndex builder via a
new module flag "EnableSplitLTOUnit", which is propagated onto a flag
on the summary index.
This is then used during the LTO link to check whether all linked
summaries were built with the same value of this flag. If not, an error
is issued when we detect a situation requiring whole program visibility
of the class hierarchy. This is the case when both of the following
conditions are met:
1) We are performing LowerTypeTests or Whole Program Devirtualization.
2) There are type tests or type checked loads in the code.
Note I have also changed the ThinLTOBitcodeWriter to also gate the
module splitting on the value of this flag.
Reviewers: pcc
Subscribers: ormris, mehdi_amini, Prazek, inglorion, eraman, steven_wu, dexonsmith, arphaman, dang, llvm-commits
Differential Revision: https://reviews.llvm.org/D53890
llvm-svn: 350948
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Summary:
LowerTypeTests moves some function definitions from individual object
files to the merged module, leaving a stub to be called in the merged
module's jump table. If an alias was pointing to such a function
definition LowerTypeTests would fail because the alias would be left
without a definition to point to.
This change 1) emits information about aliases to the ThinLTO summary,
2) replaces aliases pointing to function definitions that are moved to
the merged module with function declarations, and 3) re-emits those
aliases in the merged module pointing to the correct function
definitions.
The patch does not correctly fix all possible mis-uses of aliases in
LowerTypeTests. For example, it does not handle aliases with a different
type from the pointed to function.
The addition of alias data increases the size of Chrome build artifacts
by less than 1%.
Reviewers: pcc
Reviewed By: pcc
Subscribers: mehdi_amini, eraman, mgrang, llvm-commits, eugenis, kcc
Differential Revision: https://reviews.llvm.org/D41741
llvm-svn: 322139
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