diff --git a/llvm/include/llvm/MC/MCAsmLayout.h b/llvm/include/llvm/MC/MCAsmLayout.h
--- a/llvm/include/llvm/MC/MCAsmLayout.h
+++ b/llvm/include/llvm/MC/MCAsmLayout.h
@@ -49,6 +49,10 @@
   /// Get the assembler object this is a layout for.
   MCAssembler &getAssembler() const { return Assembler; }
 
+  /// \returns whether the offset of fragment \p F can be obtained via
+  /// getFragmentOffset.
+  bool canGetFragmentOffset(const MCFragment *F) const;
+
   /// Invalidate the fragments starting with F because it has been
   /// resized. The fragment's size should have already been updated, but
   /// its bundle padding will be recomputed.
diff --git a/llvm/include/llvm/MC/MCFragment.h b/llvm/include/llvm/MC/MCFragment.h
--- a/llvm/include/llvm/MC/MCFragment.h
+++ b/llvm/include/llvm/MC/MCFragment.h
@@ -65,6 +65,9 @@
 
   FragmentType Kind;
 
+  /// Whether fragment is being laid out.
+  bool IsBeingLaidOut;
+
 protected:
   bool HasInstructions;
 
diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
--- a/llvm/lib/MC/MCAssembler.cpp
+++ b/llvm/lib/MC/MCAssembler.cpp
@@ -397,6 +397,9 @@
   assert((!Prev || isFragmentValid(Prev)) &&
          "Attempt to compute fragment before its predecessor!");
 
+  assert(!F->IsBeingLaidOut && "Already being laid out!");
+  F->IsBeingLaidOut = true;
+
   ++stats::FragmentLayouts;
 
   // Compute fragment offset and size.
@@ -404,6 +407,7 @@
     F->Offset = Prev->Offset + getAssembler().computeFragmentSize(*this, *Prev);
   else
     F->Offset = 0;
+  F->IsBeingLaidOut = false;
   LastValidFragment[F->getParent()] = F;
 
   // If bundling is enabled and this fragment has instructions in it, it has to
diff --git a/llvm/lib/MC/MCExpr.cpp b/llvm/lib/MC/MCExpr.cpp
--- a/llvm/lib/MC/MCExpr.cpp
+++ b/llvm/lib/MC/MCExpr.cpp
@@ -547,8 +547,10 @@
   if (!Asm->getWriter().isSymbolRefDifferenceFullyResolved(*Asm, A, B, InSet))
     return;
 
-  if (SA.getFragment() == SB.getFragment() && !SA.isVariable() &&
-      !SA.isUnset() && !SB.isVariable() && !SB.isUnset()) {
+  MCFragment *FA = SA.getFragment();
+  MCFragment *FB = SB.getFragment();
+  if (FA == FB && !SA.isVariable() && !SA.isUnset() && !SB.isVariable() &&
+      !SB.isUnset()) {
     Addend += (SA.getOffset() - SB.getOffset());
 
     // Pointers to Thumb symbols need to have their low-bit set to allow
@@ -570,12 +572,17 @@
   if (!Layout)
     return;
 
-  const MCSection &SecA = *SA.getFragment()->getParent();
-  const MCSection &SecB = *SB.getFragment()->getParent();
+  const MCSection &SecA = *FA->getParent();
+  const MCSection &SecB = *FB->getParent();
 
   if ((&SecA != &SecB) && !Addrs)
     return;
 
+  // One of the symbol involved is part of a fragment being laid out. Quit now
+  // to avoid a self loop.
+  if (!Layout->canGetFragmentOffset(FA) || !Layout->canGetFragmentOffset(FB))
+    return;
+
   // Eagerly evaluate.
   Addend += Layout->getSymbolOffset(A->getSymbol()) -
             Layout->getSymbolOffset(B->getSymbol());
diff --git a/llvm/lib/MC/MCFragment.cpp b/llvm/lib/MC/MCFragment.cpp
--- a/llvm/lib/MC/MCFragment.cpp
+++ b/llvm/lib/MC/MCFragment.cpp
@@ -48,6 +48,25 @@
   return F->getLayoutOrder() <= LastValid->getLayoutOrder();
 }
 
+bool MCAsmLayout::canGetFragmentOffset(const MCFragment *F) const {
+  MCSection *Sec = F->getParent();
+  MCSection::iterator I;
+  if (MCFragment *LastValid = LastValidFragment[Sec]) {
+    // Fragment already valid, offset is available.
+    if (F->getLayoutOrder() <= LastValid->getLayoutOrder())
+      return true;
+    I = ++MCSection::iterator(LastValid);
+  } else
+    I = Sec->begin();
+
+  // A fragment ordered before F is currently being laid out.
+  const MCFragment *FirstInvalidFragment = &*I;
+  if (FirstInvalidFragment->IsBeingLaidOut)
+    return false;
+
+  return true;
+}
+
 void MCAsmLayout::invalidateFragmentsFrom(MCFragment *F) {
   // If this fragment wasn't already valid, we don't need to do anything.
   if (!isFragmentValid(F))
@@ -235,7 +254,7 @@
 MCFragment::MCFragment(FragmentType Kind, bool HasInstructions,
                        MCSection *Parent)
     : Parent(Parent), Atom(nullptr), Offset(~UINT64_C(0)), LayoutOrder(0),
-      Kind(Kind), HasInstructions(HasInstructions) {
+      Kind(Kind), IsBeingLaidOut(false), HasInstructions(HasInstructions) {
   if (Parent && !isa<MCDummyFragment>(*this))
     Parent->getFragmentList().push_back(this);
 }
diff --git a/llvm/test/MC/AsmParser/layout-interdependency.s b/llvm/test/MC/AsmParser/layout-interdependency.s
new file mode 100644
--- /dev/null
+++ b/llvm/test/MC/AsmParser/layout-interdependency.s
@@ -0,0 +1,10 @@
+# RUN: not llvm-mc --filetype=obj %s -o /dev/null 2>&1 | FileCheck %s
+
+fct_end:
+
+# CHECK: layout-interdependency.s:[[#@LINE+1]]:7: error: expected assembly-time absolute expression
+.fill (data_start - fct_end), 1, 42
+# CHECK: layout-interdependency.s:[[#@LINE+1]]:7: error: expected assembly-time absolute expression
+.fill (fct_end - data_start), 1, 42
+
+data_start: