From c1eff79f61ff76e181fa73e0478d14a9d3d58008 Mon Sep 17 00:00:00 2001
From: Rafael Espindola <rafael.espindola@gmail.com>
Date: Fri, 30 Sep 2016 06:37:29 +0000
Subject: [PATCH] Fix --gc-sections crash.

We would crash when a non-alloca section pointed to a gced part of a
merge section.

That can happen when a C/c++ constant in put in a merge section and
debug info is present.

llvm-svn: 282845
---
 lld/ELF/InputSection.cpp                      |  4 +++-
 lld/test/ELF/gc-sections-non-alloc-to-merge.s | 21 +++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)
 create mode 100644 lld/test/ELF/gc-sections-non-alloc-to-merge.s

diff --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
index 964bf392dd86..1c01972fc8a1 100644
--- a/lld/ELF/InputSection.cpp
+++ b/lld/ELF/InputSection.cpp
@@ -623,7 +623,9 @@ typename ELFT::uint MergeInputSection<ELFT>::getOffset(uintX_t Offset) const {
   // If Offset is not at beginning of a section piece, it is not in the map.
   // In that case we need to search from the original section piece vector.
   const SectionPiece &Piece = *this->getSectionPiece(Offset);
-  assert(Piece.Live);
+  if (!Piece.Live)
+    return 0;
+
   uintX_t Addend = Offset - Piece.InputOff;
   return Piece.OutputOff + Addend;
 }
diff --git a/lld/test/ELF/gc-sections-non-alloc-to-merge.s b/lld/test/ELF/gc-sections-non-alloc-to-merge.s
new file mode 100644
index 000000000000..cdc11de88893
--- /dev/null
+++ b/lld/test/ELF/gc-sections-non-alloc-to-merge.s
@@ -0,0 +1,21 @@
+# REQUIRES: x86
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
+# RUN: ld.lld %t.o -o %t --gc-sections
+# RUN: llvm-readobj -s --elf-output-style=GNU %t | FileCheck %s
+
+# CHECK:  .merge1     PROGBITS    {{[0-9a-z]*}} {{[0-9a-z]*}} 000004
+
+        .global _start
+_start:
+        .quad .Lfoo
+
+        .section        .merge1,"aM",@progbits,4
+        .p2align        2
+.Lfoo:
+        .long 1
+.Lbar:
+        .long 2
+
+        .section bar
+        .quad .Lbar
-- 
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