Add a -exported-symbol option to llvm-lto.

Patch by Tom Roeder.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191825 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 17 insertions, 0 deletions

diff --git a/test/LTO/cfi_endproc.ll b/test/LTO/cfi_endproc.ll
index ecb0ed5..11646c7 100644
--- a/test/LTO/cfi_endproc.ll
+++ b/test/LTO/cfi_endproc.ll
@@ -1,5 +1,8 @@
 ; RUN: llvm-as < %s >%t1
 ; RUN: llvm-lto -o %t2 %t1
+; RUN: llvm-nm %t2 | FileCheck %s -check-prefix=NOEXPORT
+; RUN: llvm-lto -o %t3 -exported-symbol=main %t1
+; RUN: llvm-nm %t3 | FileCheck %s -check-prefix=EXPORT
 
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
@@ -13,7 +16,11 @@ module asm ".cfi_endproc"
 
 declare void @PR14512()
 
+; Without -exported-symbol, main should be eliminated by LTO.
+; With -exported-symbol=main, main should be preserved by LTO.
 define i32 @main(i32 %argc, i8** %argv) {
+; NOEXPORT-NOT: main
+; EXPORT: main
   call void @PR14512()
   ret i32 0
 }
diff --git a/tools/llvm-lto/llvm-lto.cpp b/tools/llvm-lto/llvm-lto.cpp
index ab1e162..3ecd13f 100644
--- a/tools/llvm-lto/llvm-lto.cpp
+++ b/tools/llvm-lto/llvm-lto.cpp
@@ -45,6 +45,12 @@ OutputFilename("o", cl::init(""),
   cl::desc("Override output filename"),
   cl::value_desc("filename"));
 
+static cl::list<std::string>
+ExportedSymbols("exported-symbol",
+  cl::desc("Symbol to export from the resulting object file"),
+  cl::ZeroOrMore);
+
+
 int main(int argc, char **argv) {
   // Print a stack trace if we signal out.
   sys::PrintStackTraceOnErrorSignal();
@@ -107,6 +113,10 @@ int main(int argc, char **argv) {
     }
   }
 
+  // Add all the exported symbols to the table of symbols to preserve.
+  for (unsigned i = 0; i < ExportedSymbols.size(); ++i)
+    CodeGen.addMustPreserveSymbol(ExportedSymbols[i].c_str());
+
   if (!OutputFilename.empty()) {
     size_t len = 0;
     std::string ErrorInfo;