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[ThinLTO] Optionally ignore empty index file

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Summary:
In order to simplify distributed build system integration, where actions
may be scheduled before the Thin Link which determines the list of
objects selected by the linker. The gold plugin currently will emit
0-sized index files for objects not selected by the link, to enable
checking for expected output files by the build system. If the build
system then schedules a backend action for these bitcode files, we want
to be able to fall back to normal compilation instead of failing.

This is the LLVM side support for optionally enabling fallback
instead of issuing an error. Return a null CombinedIndex from
llvm::getModuleSummaryIndexForFile under the option when the file
is empty. Clang can then ignore the index when it is null.

Clang patch is D28362.

Reviewers: mehdi_amini

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D28410

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291302 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Teresa Johnson 2017-01-06 23:37:17 +00:00
parent 41b68ffb50
commit 12722f7e6c
1 changed files with 8 additions and 0 deletions
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8
lib/Object/ModuleSummaryIndexObjectFile.cpp
View File

@ -22,6 +22,12 @@
using namespace llvm;
using namespace object;
static llvm::cl::opt<bool> IgnoreEmptyThinLTOIndexFile(
"ignore-empty-index-file", llvm::cl::ZeroOrMore,
llvm::cl::desc(
"Ignore an empty index file and perform non-ThinLTO compilation"),
llvm::cl::init(false));
ModuleSummaryIndexObjectFile::ModuleSummaryIndexObjectFile(
MemoryBufferRef Object, std::unique_ptr<ModuleSummaryIndex> I)
: SymbolicFile(Binary::ID_ModuleSummaryIndex, Object), Index(std::move(I)) {
@ -97,6 +103,8 @@ llvm::getModuleSummaryIndexForFile(StringRef Path) {
if (EC)
return errorCodeToError(EC);
MemoryBufferRef BufferRef = (FileOrErr.get())->getMemBufferRef();
if (IgnoreEmptyThinLTOIndexFile && !BufferRef.getBufferSize())
return nullptr;
Expected<std::unique_ptr<object::ModuleSummaryIndexObjectFile>> ObjOrErr =
object::ModuleSummaryIndexObjectFile::create(BufferRef);
if (!ObjOrErr)