[LTO] Fix (wrong) TLS attribute mismatch

[davide]

Summary

When we undefine, we also preserve type of symbol so that we get it right in the combined LTO object.

[davide]

Fixes https://llvm.org/bugs/show_bug.cgi?id=27956

[• rafael]

LGTM

test/ELF/lto/tls-preserve.ll

12

Simplify, you don't need the arguments for example.

ELF/LTO.cpp

       Mover(*Combined) {}
 
 static void undefine(Symbol *S) {
-  replaceBody<Undefined>(S, S->body()->getName(), STV_DEFAULT, 0);
+  replaceBody<Undefined>(S, S->body()->getName(), STV_DEFAULT, S->body()->Type);
 }
 
 void BitcodeCompiler::add(BitcodeFile &F) {

test/ELF/lto/tls-preserve.ll

+; TLS attribute needs to be preserved.
+; REQUIRES: x86
+; RUN: llvm-as %s -o %t1.o
+; RUN: ld.lld -shared %t1.o -m elf_x86_64 -o %t1
+; RUN: llvm-readobj -t %t1 | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@tsp_int = thread_local global i32 1, align 4
+
+define i32 @_start(i32, i8**) {
+  %val = load i32, i32* @tsp_int, align 4
+  ret i32 %val
+}
+
+; CHECK: Symbol {
+; CHECK:   Name: tsp_int
+; CHECK-NEXT:   Value: 0x0
+; CHECK-NEXT:   Size: 4
+; CHECK-NEXT:   Binding: Global
+; CHECK-NEXT:   Type: TLS
+; CHECK-NEXT:   Other: 0
+; CHECK-NEXT:   Section: .tdata
+; CHECK-NEXT: }