[ThinLTO] Enable importing of aliases as copy of aliasee

Summary:
This implements a missing feature to allow importing of aliases, which
was previously disabled because alias cannot be available_externally.
We instead import an alias as a copy of its aliasee.

Some additional work was required in the IndexBitcodeWriter for the
distributed build case, to ensure that the aliasee has a value id
in the distributed index file (i.e. even when it is not being
imported directly).

This is a performance win in codes that have many aliases, e.g. C++
applications that have many constructor and destructor aliases.

Reviewers: pcc

Subscribers: mehdi_amini, inglorion, eraman, llvm-commits

Differential Revision: https://reviews.llvm.org/D40747

llvm-svn: 320895

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/IR/Value.cpp b/llvm/lib/IR/Value.cpp
index 50235d8d30f..19b2535fbd6 100644
--- a/llvm/lib/IR/Value.cpp
+++ b/llvm/lib/IR/Value.cpp
@@ -409,7 +409,7 @@ void Value::doRAUW(Value *New, bool NoMetadata) {
   if (!NoMetadata && isUsedByMetadata())
     ValueAsMetadata::handleRAUW(this, New);
 
-  while (!use_empty()) {
+  while (!materialized_use_empty()) {
     Use &U = *UseList;
     // Must handle Constants specially, we cannot call replaceUsesOfWith on a
     // constant because they are uniqued.