diff --git a/include/llvm/MC/MCMachObjectWriter.h b/include/llvm/MC/MCMachObjectWriter.h
index 3d270ce7e0d..eb2789b90f9 100644
--- a/include/llvm/MC/MCMachObjectWriter.h
+++ b/include/llvm/MC/MCMachObjectWriter.h
@@ -262,6 +262,7 @@ public:
 
   bool IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
                                               const MCSymbolData &DataA,
+                                              const MCSymbolData *DataB,
                                               const MCFragment &FB,
                                               bool InSet,
                                               bool IsPCRel) const override;
diff --git a/include/llvm/MC/MCObjectWriter.h b/include/llvm/MC/MCObjectWriter.h
index fcfa968362b..2965ce21b82 100644
--- a/include/llvm/MC/MCObjectWriter.h
+++ b/include/llvm/MC/MCObjectWriter.h
@@ -91,12 +91,12 @@ public:
                                           const MCSymbolRefExpr *B,
                                           bool InSet) const;
 
-  virtual bool
-  IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
-                                         const MCSymbolData &DataA,
-                                         const MCFragment &FB,
-                                         bool InSet,
-                                         bool IsPCRel) const;
+  virtual bool IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
+                                                      const MCSymbolData &DataA,
+                                                      const MCSymbolData *DataB,
+                                                      const MCFragment &FB,
+                                                      bool InSet,
+                                                      bool IsPCRel) const;
 
   /// \brief True if this symbol (which is a variable) is weak. This is not
   /// just STB_WEAK, but more generally whether or not we can evaluate
diff --git a/lib/MC/ELFObjectWriter.cpp b/lib/MC/ELFObjectWriter.cpp
index 2004b1b8a2d..6105b25b8bf 100644
--- a/lib/MC/ELFObjectWriter.cpp
+++ b/lib/MC/ELFObjectWriter.cpp
@@ -300,6 +300,7 @@ class ELFObjectWriter : public MCObjectWriter {
     bool
     IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
                                            const MCSymbolData &DataA,
+                                           const MCSymbolData *DataB,
                                            const MCFragment &FB,
                                            bool InSet,
                                            bool IsPCRel) const override;
@@ -619,7 +620,7 @@ void ELFObjectWriter::WriteSymbol(SymbolTableWriter &Writer, ELFSymbolData &MSD,
 
   if (ESize) {
     int64_t Res;
-    if (!ESize->EvaluateAsAbsolute(Res, Layout))
+    if (!ESize->evaluateKnownAbsolute(Res, Layout))
       report_fatal_error("Size expression must be absolute.");
     Size = Res;
   }
@@ -1765,16 +1766,14 @@ void ELFObjectWriter::WriteObject(MCAssembler &Asm,
     WriteDataSectionData(Asm, Layout, *Sections[i]);
 }
 
-bool
-ELFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
-                                                      const MCSymbolData &DataA,
-                                                      const MCFragment &FB,
-                                                      bool InSet,
-                                                      bool IsPCRel) const {
-  if (::isWeak(DataA))
+bool ELFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(
+    const MCAssembler &Asm, const MCSymbolData &DataA,
+    const MCSymbolData *DataB, const MCFragment &FB, bool InSet,
+    bool IsPCRel) const {
+  if (!InSet && (::isWeak(DataA) || (DataB && ::isWeak(*DataB))))
     return false;
   return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(
-                                                 Asm, DataA, FB,InSet, IsPCRel);
+      Asm, DataA, DataB, FB, InSet, IsPCRel);
 }
 
 bool ELFObjectWriter::isWeak(const MCSymbolData &SD) const {
diff --git a/lib/MC/MCAssembler.cpp b/lib/MC/MCAssembler.cpp
index 857eafc0b7e..d7ca875f297 100644
--- a/lib/MC/MCAssembler.cpp
+++ b/lib/MC/MCAssembler.cpp
@@ -502,9 +502,8 @@ bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout,
         IsResolved = false;
       } else {
         const MCSymbolData &DataA = getSymbolData(SA);
-        IsResolved =
-          getWriter().IsSymbolRefDifferenceFullyResolvedImpl(*this, DataA,
-                                                             *DF, false, true);
+        IsResolved = getWriter().IsSymbolRefDifferenceFullyResolvedImpl(
+            *this, DataA, nullptr, *DF, false, true);
       }
     }
   } else {
diff --git a/lib/MC/MCObjectWriter.cpp b/lib/MC/MCObjectWriter.cpp
index 3c536ecc9fd..33e4556e102 100644
--- a/lib/MC/MCObjectWriter.cpp
+++ b/lib/MC/MCObjectWriter.cpp
@@ -35,18 +35,14 @@ bool MCObjectWriter::IsSymbolRefDifferenceFullyResolved(
   if(!DataA.getFragment() || !DataB.getFragment())
     return false;
 
-  return IsSymbolRefDifferenceFullyResolvedImpl(Asm, DataA,
-                                                *DataB.getFragment(),
-                                                InSet,
-                                                false);
+  return IsSymbolRefDifferenceFullyResolvedImpl(
+      Asm, DataA, &DataB, *DataB.getFragment(), InSet, false);
 }
 
-bool
-MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
-                                                      const MCSymbolData &DataA,
-                                                      const MCFragment &FB,
-                                                      bool InSet,
-                                                      bool IsPCRel) const {
+bool MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(
+    const MCAssembler &Asm, const MCSymbolData &DataA,
+    const MCSymbolData *DataB, const MCFragment &FB, bool InSet,
+    bool IsPCRel) const {
   const MCSection &SecA = DataA.getSymbol().AliasedSymbol().getSection();
   const MCSection &SecB = FB.getParent()->getSection();
   // On ELF and COFF  A - B is absolute if A and B are in the same section.
diff --git a/lib/MC/MachObjectWriter.cpp b/lib/MC/MachObjectWriter.cpp
index 56cccab1d39..93ff75211c4 100644
--- a/lib/MC/MachObjectWriter.cpp
+++ b/lib/MC/MachObjectWriter.cpp
@@ -660,6 +660,7 @@ void MachObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
 bool MachObjectWriter::
 IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
                                        const MCSymbolData &DataA,
+                                       const MCSymbolData *DataB,
                                        const MCFragment &FB,
                                        bool InSet,
                                        bool IsPCRel) const {
diff --git a/lib/MC/WinCOFFObjectWriter.cpp b/lib/MC/WinCOFFObjectWriter.cpp
index ff90b7c2cef..b62b342edd1 100644
--- a/lib/MC/WinCOFFObjectWriter.cpp
+++ b/lib/MC/WinCOFFObjectWriter.cpp
@@ -172,6 +172,7 @@ public:
 
   bool IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
                                               const MCSymbolData &DataA,
+                                              const MCSymbolData *DataB,
                                               const MCFragment &FB, bool InSet,
                                               bool IsPCRel) const override;
 
@@ -649,16 +650,17 @@ void WinCOFFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
 }
 
 bool WinCOFFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(
-    const MCAssembler &Asm, const MCSymbolData &DataA, const MCFragment &FB,
-    bool InSet, bool IsPCRel) const {
+    const MCAssembler &Asm, const MCSymbolData &DataA,
+    const MCSymbolData *DataB, const MCFragment &FB, bool InSet,
+    bool IsPCRel) const {
   // MS LINK expects to be able to replace all references to a function with a
   // thunk to implement their /INCREMENTAL feature.  Make sure we don't optimize
   // away any relocations to functions.
   if ((((DataA.getFlags() & COFF::SF_TypeMask) >> COFF::SF_TypeShift) >>
        COFF::SCT_COMPLEX_TYPE_SHIFT) == COFF::IMAGE_SYM_DTYPE_FUNCTION)
     return false;
-  return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(Asm, DataA, FB,
-                                                                InSet, IsPCRel);
+  return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(
+      Asm, DataA, DataB, FB, InSet, IsPCRel);
 }
 
 bool WinCOFFObjectWriter::isWeak(const MCSymbolData &SD) const {
diff --git a/test/MC/ELF/weak-diff2.s b/test/MC/ELF/weak-diff2.s
new file mode 100644
index 00000000000..daf64a44232
--- /dev/null
+++ b/test/MC/ELF/weak-diff2.s
@@ -0,0 +1,10 @@
+// RUN: not llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o %t 2>&1 | FileCheck %s
+
+// CHECK: error: Cannot represent a subtraction with a weak symbol
+
+.weak f
+f:
+    nop
+g:
+    nop
+.quad g - f