[lld-link] preserve @llvm.used symbols in LTO
Summary:
We translate @llvm.used to COFF by generating /include directives
in the .drectve section. However, in LTO links, this happens after
directives have already been processed, so the new directives do
not take effect. This change marks @llvm.used symbols as GCRoots
so that they are preserved as intended.
Fixes PR40733.
Reviewers: rnk, pcc, ruiu
Reviewed By: ruiu
Subscribers: mehdi_amini, steven_wu, dexonsmith, dang, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D58255
git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@354410 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/COFF/InputFiles.cpp b/COFF/InputFiles.cpp
index 1ebb5da..ae68cbe 100644
--- a/COFF/InputFiles.cpp
+++ b/COFF/InputFiles.cpp
@@ -688,6 +688,8 @@
Sym = Symtab->addRegular(this, SymName);
}
Symbols.push_back(Sym);
+ if (ObjSym.isUsed())
+ Config->GCRoot.push_back(Sym);
}
Directives = Obj->getCOFFLinkerOpts();
}
diff --git a/test/COFF/used-lto.ll b/test/COFF/used-lto.ll
new file mode 100644
index 0000000..c269fba
--- /dev/null
+++ b/test/COFF/used-lto.ll
@@ -0,0 +1,15 @@
+; REQUIRES: x86
+; RUN: llvm-as -o %t.obj %s
+; RUN: lld-link -dll -debug -opt:ref -noentry -out:%t.dll %t.obj
+; RUN: llvm-pdbutil dump -publics %t.pdb | FileCheck %s
+
+; CHECK: S_PUB32 {{.*}} `foo`
+
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+
+@llvm.used = appending global [1 x i8*] [i8* bitcast (void ()* @foo to i8*)], section "llvm.metadata"
+
+define void @foo() {
+ ret void
+}
