This patch fixes LTO's RecordStreamer so that it records symbols in the MCExpr

part of an asm .symver directive as being used. This prevents referenced
functions from being internalized and deleted.

Without the patch to LTOModule.cpp, the test case will produce the error:

LLVM ERROR: A @@ version cannot be undefined.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205221 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/LTO/LTOModule.cpp b/lib/LTO/LTOModule.cpp
index cffc9aaf7e2883e29d896ed0c88a5a4d27f532fd..567da04f90cc4d7c724f71d745b474edc2e4c1d2 100644 (file)
--- a/lib/LTO/LTOModule.cpp
+++ b/lib/LTO/LTOModule.cpp
@@ -660,6 +660,7 @@ namespace {
     void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) override {
       // FIXME: should we handle aliases?
       markDefined(*Symbol);
+      AddValueSymbols(Value);
     }
     bool EmitSymbolAttribute(MCSymbol *Symbol,
                              MCSymbolAttr Attribute) override {

diff --git a/test/LTO/symver-asm.ll b/test/LTO/symver-asm.ll
new file mode 100644 (file)
index 0000000..03dda2b
--- /dev/null
+++ b/test/LTO/symver-asm.ll
@@ -0,0 +1,16 @@
+; RUN: llvm-as < %s >%t1
+; RUN: llvm-lto -o %t2 %t1
+; RUN: llvm-nm %t2 | FileCheck %s
+
+target triple = "x86_64-unknown-linux-gnu"
+
+module asm ".symver io_cancel_0_4,io_cancel@@LIBAIO_0.4"
+
+; Even without -exported-symbol, io_cancel_0_4 should be noticed by LTOModule's
+; RecordStreamer, so it shouldn't get eliminated. However, the object file will
+; contain the aliased symver as well as the original.
+define i32 @io_cancel_0_4() {
+; CHECK: io_cancel@@LIBAIO_0.4
+; CHECK: io_cancel_0_4
+  ret i32 0
+}