From 9be24cf516c79322e53d2d7b3a391117c4460883 Mon Sep 17 00:00:00 2001
From: Rafael Espindola <rafael.espindola@gmail.com>
Date: Wed, 20 Sep 2017 18:30:57 +0000
Subject: [PATCH] Fix assigning to _gp in linker scripts.

The previous logic was to try to detect if a linker script defined _gp
by checking !ElfSym::MipsGp->Value. That doesn't work in all cases as
the assigned value can be 0.

We now just always defined it Writer.cpp and always overwrite it
afterwards if needed.

llvm-svn: 313788
---
 lld/ELF/LinkerScript.cpp   | 1 +
 lld/ELF/Writer.cpp         | 2 +-
 lld/test/ELF/mips-gp-ext.s | 7 +++++++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index af8398290e67..3ed6ad090938 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -148,6 +148,7 @@ void LinkerScript::assignSymbol(SymbolAssignment *Cmd, bool InSec) {
   ExprValue V = Cmd->Expression();
   if (V.isAbsolute()) {
     Sym->Value = V.getValue();
+    Sym->Section = nullptr;
   } else {
     Sym->Section = V.Sec;
     Sym->Value = V.getSectionOffset();
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index 6dd3d9f92418..b4342a93c560 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -964,7 +964,7 @@ template <class ELFT> void Writer<ELFT>::setReservedSymbolSections() {
 
   // Setup MIPS _gp_disp/__gnu_local_gp symbols which should
   // be equal to the _gp symbol's value.
-  if (ElfSym::MipsGp && !ElfSym::MipsGp->Value) {
+  if (ElfSym::MipsGp) {
     // Find GP-relative section with the lowest address
     // and use this address to calculate default _gp value.
     for (OutputSection *OS : OutputSections) {
diff --git a/lld/test/ELF/mips-gp-ext.s b/lld/test/ELF/mips-gp-ext.s
index 98b9cbc06d28..2fd21b7a9818 100644
--- a/lld/test/ELF/mips-gp-ext.s
+++ b/lld/test/ELF/mips-gp-ext.s
@@ -10,6 +10,13 @@
 # RUN: ld.lld -shared -o %t.rel.so --script %t.rel.script %t.o
 # RUN: llvm-objdump -s -t %t.rel.so | FileCheck --check-prefix=REL %s
 
+# RUN: echo "SECTIONS { \
+# RUN:          .text : { *(.text) } \
+# RUN:          _gp = 0x100 + ABSOLUTE(.); \
+# RUN:          .got  : { *(.got) } }" > %t.rel.script
+# RUN: ld.lld -shared -o %t.rel.so --script %t.rel.script %t.o
+# RUN: llvm-objdump -s -t %t.rel.so | FileCheck --check-prefix=REL %s
+
 # RUN: echo "SECTIONS { \
 # RUN:          .text : { *(.text) } \
 # RUN:          _gp = 0x200; \