[llvm] r308504 - LTO: Export functions referenced by the CFI jump table.

[Peter Collingbourne via llvm-commits]

Author: pcc
Date: Wed Jul 19 11:18:19 2017
New Revision: 308504

URL: http://llvm.org/viewvc/llvm-project?rev=308504&view=rev
Log:
LTO: Export functions referenced by the CFI jump table.

If the LowerTypeTests pass decides to add a function to a jump
table for CFI, it will add its name to the set cfiFunctionDefs,
which among other things will cause the function to be renamed in
the ThinLTO backend.

One other thing that we must do with such functions is to not
internalize them, because the jump table in the full LTO object will
contain a reference to the actual function body in the ThinLTO object.

This patch handles that by ensuring that we export any functions
whose names appear in the cfiFunctionDefs set.

Fixes PR33831.

Differential Revision: https://reviews.llvm.org/D35605

Added:
    llvm/trunk/test/LTO/Resolution/X86/export-jumptable.ll
Modified:
    llvm/trunk/lib/LTO/LTO.cpp

Modified: llvm/trunk/lib/LTO/LTO.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/LTO/LTO.cpp?rev=308504&r1=308503&r2=308504&view=diff
==============================================================================
--- llvm/trunk/lib/LTO/LTO.cpp (original)
+++ llvm/trunk/lib/LTO/LTO.cpp Wed Jul 19 11:18:19 2017
@@ -1072,6 +1072,12 @@ Error LTO::runThinLTO(AddStreamFn AddStr
         ExportedGUIDs.insert(GUID);
     }
 
+    // Any functions referenced by the jump table in the regular LTO object must
+    // be exported.
+    for (auto &Def : ThinLTO.CombinedIndex.cfiFunctionDefs())
+      ExportedGUIDs.insert(
+          GlobalValue::getGUID(GlobalValue::dropLLVMManglingEscape(Def)));
+
     auto isExported = [&](StringRef ModuleIdentifier, GlobalValue::GUID GUID) {
       const auto &ExportList = ExportLists.find(ModuleIdentifier);
       return (ExportList != ExportLists.end() &&

Added: llvm/trunk/test/LTO/Resolution/X86/export-jumptable.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/LTO/Resolution/X86/export-jumptable.ll?rev=308504&view=auto
==============================================================================
--- llvm/trunk/test/LTO/Resolution/X86/export-jumptable.ll (added)
+++ llvm/trunk/test/LTO/Resolution/X86/export-jumptable.ll Wed Jul 19 11:18:19 2017
@@ -0,0 +1,32 @@
+; Test that we do not internalize functions that appear in the CFI jump table in
+; the full LTO object file; any such functions will be referenced by the jump
+; table.
+
+; RUN: opt -thinlto-bc -o %t %s
+; RUN: llvm-lto2 run -o %t2 -r %t,f1,p -r %t,f2,p -r %t,_start,px %t -save-temps
+; RUN: llvm-dis %t2.1.2.internalize.bc -o - | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; CHECK: define void @f1()
+define void @f1() !type !0 {
+  ret void
+}
+
+; CHECK: define internal void @f2()
+define void @f2() !type !1 {
+  ret void
+}
+
+define i1 @_start(i8* %p) {
+  %1 = call i1 @llvm.type.test(i8* %p, metadata !"typeid1")
+  call void @f1()
+  call void @f2()
+  ret i1 %1
+}
+
+declare i1 @llvm.type.test(i8*, metadata)
+
+!0 = !{i64 0, !"typeid1"}
+!1 = !{i64 0, !"typeid2"}