[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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@320895 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 21 insertions, 8 deletions

diff --git a/test/ThinLTO/X86/distributed_import.ll b/test/ThinLTO/X86/distributed_import.ll
index e7e4904d52b..365fbd9b0f7 100644
--- a/test/ThinLTO/X86/distributed_import.ll
+++ b/test/ThinLTO/X86/distributed_import.ll
@@ -10,11 +10,15 @@
 ; RUN: llvm-lto2 run %t1.bc %t2.bc -o %t.o -save-temps \
 ; RUN:     -thinlto-distributed-indexes \
 ; RUN:     -r=%t1.bc,g, \
+; RUN:     -r=%t1.bc,analias, \
 ; RUN:     -r=%t1.bc,f,px \
-; RUN:     -r=%t2.bc,g,px
-; RUN: opt -function-import -summary-file %t1.bc.thinlto.bc %t1.bc -o %t1.out
-; RUN: opt -function-import -summary-file %t2.bc.thinlto.bc %t2.bc -o %t2.out
-; RUN: llvm-dis -o - %t2.out | FileCheck %s
+; RUN:     -r=%t2.bc,g,px \
+; RUN:     -r=%t2.bc,analias,px \
+; RUN:     -r=%t2.bc,aliasee,px
+; RUN: opt -function-import -import-all-index -summary-file %t1.bc.thinlto.bc %t1.bc -o %t1.out
+; RUN: opt -function-import -import-all-index -summary-file %t2.bc.thinlto.bc %t2.bc -o %t2.out
+; RUN: llvm-dis -o - %t1.out | FileCheck %s --check-prefix=IMPORT
+; RUN: llvm-dis -o - %t2.out | FileCheck %s --check-prefix=EXPORT
 
 ; Save the generated index files.
 ; RUN: cp %t1.bc.thinlto.bc %t1.bc.thinlto.bc.orig
@@ -34,26 +38,35 @@
 ; RUN: llvm-lto2 run %t1.bc %t2.bc -o %t.o -save-temps \
 ; RUN:     -thinlto-distributed-indexes \
 ; RUN:     -r=%t1.bc,g, \
+; RUN:     -r=%t1.bc,analias, \
 ; RUN:     -r=%t1.bc,f,px \
-; RUN:     -r=%t2.bc,g,px
+; RUN:     -r=%t2.bc,g,px \
+; RUN:     -r=%t2.bc,analias,px \
+; RUN:     -r=%t2.bc,aliasee,px
 ; RUN: diff %t1.bc.thinlto.bc.orig %t1.bc.thinlto.bc
 ; RUN: diff %t2.bc.thinlto.bc.orig %t2.bc.thinlto.bc
 
 ; Make sure importing occurs as expected
 ; RUN: cp %t1.bc.sv %t1.bc
 ; RUN: cp %t2.bc.sv %t2.bc
-; RUN: opt -function-import -summary-file %t2.bc.thinlto.bc %t2.bc -o %t2.out
-; RUN: llvm-dis -o - %t2.out | FileCheck %s
+; RUN: opt -function-import -import-all-index -summary-file %t1.bc.thinlto.bc %t1.bc -o %t1.out
+; RUN: opt -function-import -import-all-index -summary-file %t2.bc.thinlto.bc %t2.bc -o %t2.out
+; RUN: llvm-dis -o - %t1.out | FileCheck %s --check-prefix=IMPORT
+; RUN: llvm-dis -o - %t2.out | FileCheck %s --check-prefix=EXPORT
 
-; CHECK: @G.llvm.
+; IMPORT: define available_externally i32 @g() !thinlto_src_module
+; IMPORT: define available_externally void @analias() !thinlto_src_module
+; EXPORT: @G.llvm.
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 declare i32 @g(...)
+declare void @analias(...)
 
 define void @f() {
 entry:
   call i32 (...) @g()
+  call void (...) @analias()
   ret void
 }