From 2089e4c8f11aeff994c14a85b9de246538c8fd8d Mon Sep 17 00:00:00 2001
From: Hsiangkai Wang <hsiangkai@gmail.com>
Date: Wed, 1 Aug 2018 04:17:41 +0000
Subject: [PATCH] [DebugInfo] Fix build failed in
 clang-x86_64-linux-selfhost-modules.

Only generate symbol difference expression if needed.

llvm-svn: 338484
---
 llvm/lib/MC/MCAssembler.cpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
index d3a84e26f1b0..1e23b6d816e8 100644
--- a/llvm/lib/MC/MCAssembler.cpp
+++ b/llvm/lib/MC/MCAssembler.cpp
@@ -954,7 +954,13 @@ bool MCAssembler::relaxDwarfLineAddr(MCAsmLayout &Layout,
   MCContext &Context = Layout.getAssembler().getContext();
   uint64_t OldSize = DF.getContents().size();
   int64_t AddrDelta;
-  bool Abs = DF.getAddrDelta().evaluateAsAbsolute(AddrDelta, Layout);
+  bool Abs;
+  if (getBackend().requiresDiffExpressionRelocations())
+    Abs = DF.getAddrDelta().evaluateAsAbsolute(AddrDelta, Layout);
+  else {
+    Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout);
+    assert(Abs && "We created a line delta with an invalid expression");
+  }
   int64_t LineDelta;
   LineDelta = DF.getLineDelta();
   SmallVectorImpl<char> &Data = DF.getContents();