From 14b352ee16d47ecd4636004cefbced6f4f3ec6a8 Mon Sep 17 00:00:00 2001
From: Peter Collingbourne <peter@pcc.me.uk>
Date: Thu, 3 Oct 2019 23:42:44 +0000
Subject: [PATCH] LowerTypeTests: Rename local functions to avoid collisions
 with identically named functions in ThinLTO modules.

Without this we can encounter link errors or incorrect behaviour
at runtime as a result of the wrong function being referenced.

Differential Revision: https://reviews.llvm.org/D67945

llvm-svn: 373678
---
 lib/Transforms/IPO/LowerTypeTests.cpp             | 11 +++++++++++
 .../LowerTypeTests/export-rename-local.ll         | 15 +++++++++++++++
 2 files changed, 26 insertions(+)
 create mode 100644 test/Transforms/LowerTypeTests/export-rename-local.ll

diff --git a/lib/Transforms/IPO/LowerTypeTests.cpp b/lib/Transforms/IPO/LowerTypeTests.cpp
index 1b83ccb816e..36562961744 100644
--- a/lib/Transforms/IPO/LowerTypeTests.cpp
+++ b/lib/Transforms/IPO/LowerTypeTests.cpp
@@ -1887,6 +1887,17 @@ bool LowerTypeTestsModule::lower() {
         CfiFunctionLinkage Linkage = P.second.Linkage;
         MDNode *FuncMD = P.second.FuncMD;
         Function *F = M.getFunction(FunctionName);
+        if (F && F->hasLocalLinkage()) {
+          // Locally defined function that happens to have the same name as a
+          // function defined in a ThinLTO module. Rename it to move it out of
+          // the way of the external reference that we're about to create.
+          // Note that setName will find a unique name for the function, so even
+          // if there is an existing function with the suffix there won't be a
+          // name collision.
+          F->setName(F->getName() + ".1");
+          F = nullptr;
+        }
+
         if (!F)
           F = Function::Create(
               FunctionType::get(Type::getVoidTy(M.getContext()), false),
diff --git a/test/Transforms/LowerTypeTests/export-rename-local.ll b/test/Transforms/LowerTypeTests/export-rename-local.ll
new file mode 100644
index 00000000000..9e7c54ee94a
--- /dev/null
+++ b/test/Transforms/LowerTypeTests/export-rename-local.ll
@@ -0,0 +1,15 @@
+; RUN: opt -S %s -lowertypetests -lowertypetests-summary-action=export -lowertypetests-read-summary=%S/Inputs/exported-funcs.yaml | FileCheck %s
+
+; CHECK: define internal void @external_addrtaken.1()
+; CHECK: declare {{.*}} void @external_addrtaken.cfi()
+
+target triple = "x86_64-unknown-linux"
+
+define internal void @external_addrtaken() !type !1 {
+  ret void
+}
+
+!cfi.functions = !{!0}
+
+!0 = !{!"external_addrtaken", i8 0, !1}
+!1 = !{i64 0, !"typeid1"}