[LTO] Fix the interaction between linker redefined symbols and ThinLTO

This is the same as r304719 but for ThinLTO.
The substantial difference is that in this case we don't have
whole visibility, just the summary.
In the LTO case, when we got the resolution for the input file we
could just see if the linker told us whether a symbol was linker
redefined (using --wrap or --defsym) and switch the linkage directly
for the GV.

Here, we have the summary. So, we record that the linkage changed
from <whatever it was> to $weakany to prevent IPOs across this symbol
boundaries and actually just switch the linkage at FunctionImport time.

This patch should also fixes the lld bits (as all the scaffolding for
communicating if a symbol is linker redefined should be there & should
be the same), but I'll make sure to add some tests there as well.

Fixes PR33192.

Differential Revision:  https://reviews.llvm.org/D35064

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@307303 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 16 insertions, 0 deletions

diff --git a/test/LTO/Resolution/X86/linker-redef-thin.ll b/test/LTO/Resolution/X86/linker-redef-thin.ll
new file mode 100644
index 00000000000..ebaac8094e7
--- /dev/null
+++ b/test/LTO/Resolution/X86/linker-redef-thin.ll
@@ -0,0 +1,16 @@
+; RUN: opt -module-summary %s -o %t.o
+; RUN: llvm-lto2 run -o %t1.o %t.o -r %t.o,patatino,pr
+; RUN: llvm-readobj -t %t1.o.0 | FileCheck %s
+
+; CHECK: Name: patatino
+; CHECK-NEXT: Value:
+; CHECK-NEXT: Size:
+; CHECK-NEXT: Binding: Weak
+; CHECK-NEXT: Type: Function
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @patatino() {
+  ret void
+}