[PATCH] D35605: LTO: Export functions referenced by the CFI jump table.

[Peter Collingbourne via Phabricator via llvm-commits]

pcc created this revision.
Herald added subscribers: hiraditya, inglorion, mehdi_amini.

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.


https://reviews.llvm.org/D35605

Files:
  llvm/lib/LTO/LTO.cpp
  llvm/test/LTO/Resolution/X86/export-jumptable.ll


Index: llvm/test/LTO/Resolution/X86/export-jumptable.ll
===================================================================
--- /dev/null
+++ llvm/test/LTO/Resolution/X86/export-jumptable.ll
@@ -0,0 +1,28 @@
+; 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"}
Index: llvm/lib/LTO/LTO.cpp
===================================================================
--- llvm/lib/LTO/LTO.cpp
+++ llvm/lib/LTO/LTO.cpp
@@ -1072,6 +1072,12 @@
         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() &&


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