[Assembler] Make fatal assembler errors non-fatal

Currently, if the assembler encounters an error after parsing (such as an
out-of-range fixup), it reports this as a fatal error, and so stops after the
first error. However, for most of these there is an obvious way to recover
after emitting the error, such as emitting the fixup with a value of zero. This
means that we can report on all of the errors in a file, not just the first
one. MCContext::reportError records the fact that an error was encountered, so
we won't actually emit an object file with the incorrect contents.

Differential Revision: http://reviews.llvm.org/D14717

llvm-svn: 253328

11 files changed, 219 insertions, 123 deletions

diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index 230d3d775b1..df7a606a717 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -630,28 +630,36 @@ void ELFObjectWriter::recordRelocation(MCAssembler &Asm,
     // In general, ELF has no relocations for -B. It can only represent (A + C)
     // or (A + C - R). If B = R + K and the relocation is not pcrel, we can
     // replace B to implement it: (A - R - K + C)
-    if (IsPCRel)
-      Asm.getContext().reportFatalError(
+    if (IsPCRel) {
+      Asm.getContext().reportError(
           Fixup.getLoc(),
           "No relocation available to represent this relative expression");
+      return;
+    }
 
     const auto &SymB = cast<MCSymbolELF>(RefB->getSymbol());
 
-    if (SymB.isUndefined())
-      Asm.getContext().reportFatalError(
+    if (SymB.isUndefined()) {
+      Asm.getContext().reportError(
           Fixup.getLoc(),
           Twine("symbol '") + SymB.getName() +
               "' can not be undefined in a subtraction expression");
+      return;
+    }
 
     assert(!SymB.isAbsolute() && "Should have been folded");
     const MCSection &SecB = SymB.getSection();
-    if (&SecB != &FixupSection)
-      Asm.getContext().reportFatalError(
+    if (&SecB != &FixupSection) {
+      Asm.getContext().reportError(
           Fixup.getLoc(), "Cannot represent a difference across sections");
+      return;
+    }
 
-    if (::isWeak(SymB))
-      Asm.getContext().reportFatalError(
+    if (::isWeak(SymB)) {
+      Asm.getContext().reportError(
           Fixup.getLoc(), "Cannot represent a subtraction with a weak symbol");
+      return;
+    }
 
     uint64_t SymBOffset = Layout.getSymbolOffset(SymB);
     uint64_t K = SymBOffset - FixupOffset;
@@ -784,8 +792,10 @@ void ELFObjectWriter::computeSymbolTable(
                     Renames.count(&Symbol)))
       continue;
 
-    if (Symbol.isTemporary() && Symbol.isUndefined())
-      Ctx.reportFatalError(SMLoc(), "Undefined temporary");
+    if (Symbol.isTemporary() && Symbol.isUndefined()) {
+      Ctx.reportError(SMLoc(), "Undefined temporary symbol");
+      continue;
+    }
 
     ELFSymbolData MSD;
     MSD.Symbol = cast<MCSymbolELF>(&Symbol);
diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
index 06f65fcb49a..9f3ab18a40b 100644
--- a/llvm/lib/MC/MCAssembler.cpp
+++ b/llvm/lib/MC/MCAssembler.cpp
@@ -179,14 +179,19 @@ const MCSymbol *MCAsmLayout::getBaseSymbol(const MCSymbol &Symbol) const {
 
   const MCExpr *Expr = Symbol.getVariableValue();
   MCValue Value;
-  if (!Expr->evaluateAsValue(Value, *this))
-    llvm_unreachable("Invalid Expression");
+  if (!Expr->evaluateAsValue(Value, *this)) {
+    Assembler.getContext().reportError(
+        SMLoc(), "expression could not be evaluated");
+    return nullptr;
+  }
 
   const MCSymbolRefExpr *RefB = Value.getSymB();
-  if (RefB)
-    Assembler.getContext().reportFatalError(
+  if (RefB) {
+    Assembler.getContext().reportError(
         SMLoc(), Twine("symbol '") + RefB->getSymbol().getName() +
                      "' could not be evaluated in a subtraction expression");
+    return nullptr;
+  }
 
   const MCSymbolRefExpr *A = Value.getSymA();
   if (!A)
@@ -196,9 +201,10 @@ const MCSymbol *MCAsmLayout::getBaseSymbol(const MCSymbol &Symbol) const {
   const MCAssembler &Asm = getAssembler();
   if (ASym.isCommon()) {
     // FIXME: we should probably add a SMLoc to MCExpr.
-    Asm.getContext().reportFatalError(SMLoc(),
-                                "Common symbol " + ASym.getName() +
-                                    " cannot be used in assignment expr");
+    Asm.getContext().reportError(SMLoc(),
+                                 "Common symbol '" + ASym.getName() +
+                                     "' cannot be used in assignment expr");
+    return nullptr;
   }
 
   return &ASym;
@@ -436,8 +442,13 @@ bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout,
   // probably merge the two into a single callback that tries to evaluate a
   // fixup and records a relocation if one is needed.
   const MCExpr *Expr = Fixup.getValue();
-  if (!Expr->evaluateAsRelocatable(Target, &Layout, &Fixup))
-    getContext().reportFatalError(Fixup.getLoc(), "expected relocatable expression");
+  if (!Expr->evaluateAsRelocatable(Target, &Layout, &Fixup)) {
+    getContext().reportError(Fixup.getLoc(), "expected relocatable expression");
+    // Claim to have completely evaluated the fixup, to prevent any further
+    // processing from being done.
+    Value = 0;
+    return true;
+  }
 
   bool IsPCRel = Backend.getFixupKindInfo(
     Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
diff --git a/llvm/lib/MC/WinCOFFObjectWriter.cpp b/llvm/lib/MC/WinCOFFObjectWriter.cpp
index 8d4d3df21ab..7eb470353b7 100644
--- a/llvm/lib/MC/WinCOFFObjectWriter.cpp
+++ b/llvm/lib/MC/WinCOFFObjectWriter.cpp
@@ -706,14 +706,17 @@ void WinCOFFObjectWriter::recordRelocation(
 
   const MCSymbol &Symbol = Target.getSymA()->getSymbol();
   const MCSymbol &A = Symbol;
-  if (!A.isRegistered())
-    Asm.getContext().reportFatalError(Fixup.getLoc(),
+  if (!A.isRegistered()) {
+    Asm.getContext().reportError(Fixup.getLoc(),
                                       Twine("symbol '") + A.getName() +
                                           "' can not be undefined");
+    return;
+  }
   if (A.isTemporary() && A.isUndefined()) {
-    Asm.getContext().reportFatalError(Fixup.getLoc(),
+    Asm.getContext().reportError(Fixup.getLoc(),
                                       Twine("assembler label '") + A.getName() +
                                           "' can not be undefined");
+    return;
   }
 
   MCSection *Section = Fragment->getParent();
@@ -731,17 +734,21 @@ void WinCOFFObjectWriter::recordRelocation(
 
   if (SymB) {
     const MCSymbol *B = &SymB->getSymbol();
-    if (!B->getFragment())
-      Asm.getContext().reportFatalError(
+    if (!B->getFragment()) {
+      Asm.getContext().reportError(
           Fixup.getLoc(),
           Twine("symbol '") + B->getName() +
               "' can not be undefined in a subtraction expression");
+      return;
+    }
 
-    if (!A.getFragment())
-      Asm.getContext().reportFatalError(
+    if (!A.getFragment()) {
+      Asm.getContext().reportError(
           Fixup.getLoc(),
           Twine("symbol '") + Symbol.getName() +
               "' can not be undefined in a subtraction expression");
+      return;
+    }
 
     CrossSection = &Symbol.getSection() != &B->getSection();
 
diff --git a/llvm/lib/MC/WinCOFFStreamer.cpp b/llvm/lib/MC/WinCOFFStreamer.cpp
index 02814fa7d28..a38b1a41a9b 100644
--- a/llvm/lib/MC/WinCOFFStreamer.cpp
+++ b/llvm/lib/MC/WinCOFFStreamer.cpp
@@ -122,29 +122,37 @@ void MCWinCOFFStreamer::BeginCOFFSymbolDef(MCSymbol const *Symbol) {
          "Got non-COFF section in the COFF backend!");
 
   if (CurSymbol)
-    FatalError("starting a new symbol definition without completing the "
-               "previous one");
+    Error("starting a new symbol definition without completing the "
+          "previous one");
   CurSymbol = Symbol;
 }
 
 void MCWinCOFFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
-  if (!CurSymbol)
-    FatalError("storage class specified outside of symbol definition");
+  if (!CurSymbol) {
+    Error("storage class specified outside of symbol definition");
+    return;
+  }
 
-  if (StorageClass & ~COFF::SSC_Invalid)
-    FatalError("storage class value '" + Twine(StorageClass) +
+  if (StorageClass & ~COFF::SSC_Invalid) {
+    Error("storage class value '" + Twine(StorageClass) +
                "' out of range");
+    return;
+  }
 
   getAssembler().registerSymbol(*CurSymbol);
   cast<MCSymbolCOFF>(CurSymbol)->setClass((uint16_t)StorageClass);
 }
 
 void MCWinCOFFStreamer::EmitCOFFSymbolType(int Type) {
-  if (!CurSymbol)
-    FatalError("symbol type specified outside of a symbol definition");
+  if (!CurSymbol) {
+    Error("symbol type specified outside of a symbol definition");
+    return;
+  }
 
-  if (Type & ~0xffff)
-    FatalError("type value '" + Twine(Type) + "' out of range");
+  if (Type & ~0xffff) {
+    Error("type value '" + Twine(Type) + "' out of range");
+    return;
+  }
 
   getAssembler().registerSymbol(*CurSymbol);
   cast<MCSymbolCOFF>(CurSymbol)->setType((uint16_t)Type);
@@ -152,7 +160,7 @@ void MCWinCOFFStreamer::EmitCOFFSymbolType(int Type) {
 
 void MCWinCOFFStreamer::EndCOFFSymbolDef() {
   if (!CurSymbol)
-    FatalError("ending symbol definition without starting one");
+    Error("ending symbol definition without starting one");
   CurSymbol = nullptr;
 }
 
@@ -281,9 +289,8 @@ void MCWinCOFFStreamer::FinishImpl() {
   MCObjectStreamer::FinishImpl();
 }
 
-LLVM_ATTRIBUTE_NORETURN
-void MCWinCOFFStreamer::FatalError(const Twine &Msg) const {
-  getContext().reportFatalError(SMLoc(), Msg);
+void MCWinCOFFStreamer::Error(const Twine &Msg) const {
+  getContext().reportError(SMLoc(), Msg);
 }
 }
 
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp
index 741b273073e..61c96f1d93c 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp
@@ -90,9 +90,11 @@ bool AArch64MachObjectWriter::getAArch64FixupKindMachOInfo(
     Log2Size = llvm::Log2_32(4);
     // This encompasses the relocation for the whole 21-bit value.
     switch (Sym->getKind()) {
-    default:
-      Asm.getContext().reportFatalError(Fixup.getLoc(),
-                                  "ADR/ADRP relocations must be GOT relative");
+    default: {
+      Asm.getContext().reportError(Fixup.getLoc(),
+                                   "ADR/ADRP relocations must be GOT relative");
+      return false;
+    }
     case MCSymbolRefExpr::VK_PAGE:
       RelocType = unsigned(MachO::ARM64_RELOC_PAGE21);
       return true;
@@ -170,25 +172,25 @@ void AArch64MachObjectWriter::recordRelocation(
   // assembler local symbols. If we got here, that's not what we have,
   // so complain loudly.
   if (Kind == AArch64::fixup_aarch64_pcrel_branch19) {
-    Asm.getContext().reportFatalError(Fixup.getLoc(),
-                                "conditional branch requires assembler-local"
-                                " label. '" +
-                                    Target.getSymA()->getSymbol().getName() +
-                                    "' is external.");
+    Asm.getContext().reportError(Fixup.getLoc(),
+                                 "conditional branch requires assembler-local"
+                                 " label. '" +
+                                     Target.getSymA()->getSymbol().getName() +
+                                     "' is external.");
     return;
   }
 
   // 14-bit branch relocations should only target internal labels, and so
   // should never get here.
   if (Kind == AArch64::fixup_aarch64_pcrel_branch14) {
-    Asm.getContext().reportFatalError(Fixup.getLoc(),
-                                "Invalid relocation on conditional branch!");
+    Asm.getContext().reportError(Fixup.getLoc(),
+                                 "Invalid relocation on conditional branch!");
     return;
   }
 
   if (!getAArch64FixupKindMachOInfo(Fixup, Type, Target.getSymA(), Log2Size,
-                                  Asm)) {
-    Asm.getContext().reportFatalError(Fixup.getLoc(), "unknown AArch64 fixup kind!");
+                                    Asm)) {
+    Asm.getContext().reportError(Fixup.getLoc(), "unknown AArch64 fixup kind!");
     return;
   }
 
@@ -200,8 +202,9 @@ void AArch64MachObjectWriter::recordRelocation(
     Type = MachO::ARM64_RELOC_UNSIGNED;
 
     if (IsPCRel) {
-      Asm.getContext().reportFatalError(Fixup.getLoc(),
-                                  "PC relative absolute relocation!");
+      Asm.getContext().reportError(Fixup.getLoc(),
+                                   "PC relative absolute relocation!");
+      return;
 
       // FIXME: x86_64 sets the type to a branch reloc here. Should we do
       // something similar?
@@ -229,16 +232,20 @@ void AArch64MachObjectWriter::recordRelocation(
       Writer->addRelocation(A_Base, Fragment->getParent(), MRE);
       return;
     } else if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None ||
-               Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None)
+               Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None) {
       // Otherwise, neither symbol can be modified.
-      Asm.getContext().reportFatalError(Fixup.getLoc(),
-                                  "unsupported relocation of modified symbol");
+      Asm.getContext().reportError(Fixup.getLoc(),
+                                   "unsupported relocation of modified symbol");
+      return;
+    }
 
     // We don't support PCrel relocations of differences.
-    if (IsPCRel)
-      Asm.getContext().reportFatalError(Fixup.getLoc(),
-                                  "unsupported pc-relative relocation of "
-                                  "difference");
+    if (IsPCRel) {
+      Asm.getContext().reportError(Fixup.getLoc(),
+                                   "unsupported pc-relative relocation of "
+                                   "difference");
+      return;
+    }
 
     // AArch64 always uses external relocations. If there is no symbol to use as
     // a base address (a local symbol with no preceding non-local symbol),
@@ -246,20 +253,26 @@ void AArch64MachObjectWriter::recordRelocation(
     //
     // FIXME: We should probably just synthesize an external symbol and use
     // that.
-    if (!A_Base)
-      Asm.getContext().reportFatalError(
+    if (!A_Base) {
+      Asm.getContext().reportError(
           Fixup.getLoc(),
           "unsupported relocation of local symbol '" + A->getName() +
               "'. Must have non-local symbol earlier in section.");
-    if (!B_Base)
-      Asm.getContext().reportFatalError(
+      return;
+    }
+    if (!B_Base) {
+      Asm.getContext().reportError(
           Fixup.getLoc(),
           "unsupported relocation of local symbol '" + B->getName() +
               "'. Must have non-local symbol earlier in section.");
+      return;
+    }
 
-    if (A_Base == B_Base && A_Base)
-      Asm.getContext().reportFatalError(Fixup.getLoc(),
-                                  "unsupported relocation with identical base");
+    if (A_Base == B_Base && A_Base) {
+      Asm.getContext().reportError(
+          Fixup.getLoc(), "unsupported relocation with identical base");
+      return;
+    }
 
     Value += (!A->getFragment() ? 0 : Writer->getSymbolAddress(*A, Layout)) -
              (!A_Base || !A_Base->getFragment() ? 0 : Writer->getSymbolAddress(
@@ -309,10 +322,12 @@ void AArch64MachObjectWriter::recordRelocation(
       // we need to preserve and merge with the new Target? How about
       // the FixedValue?
       if (!Symbol->getVariableValue()->evaluateAsRelocatable(Target, &Layout,
-                                                             &Fixup))
-        Asm.getContext().reportFatalError(Fixup.getLoc(),
-                                    "unable to resolve variable '" +
-                                        Symbol->getName() + "'");
+                                                             &Fixup)) {
+        Asm.getContext().reportError(Fixup.getLoc(),
+                                     "unable to resolve variable '" +
+                                         Symbol->getName() + "'");
+        return;
+      }
       return recordRelocation(Writer, Asm, Layout, Fragment, Fixup, Target,
                               FixedValue);
     }
@@ -337,11 +352,13 @@ void AArch64MachObjectWriter::recordRelocation(
         Value +=
             Layout.getSymbolOffset(*Symbol) - Layout.getSymbolOffset(*Base);
     } else if (Symbol->isInSection()) {
-      if (!CanUseLocalRelocation)
-        Asm.getContext().reportFatalError(
+      if (!CanUseLocalRelocation) {
+        Asm.getContext().reportError(
             Fixup.getLoc(),
             "unsupported relocation of local symbol '" + Symbol->getName() +
                 "'. Must have non-local symbol earlier in section.");
+        return;
+      }
       // Adjust the relocation to be section-relative.
       // The index is the section ordinal (1-based).
       const MCSection &Sec = Symbol->getSection();
@@ -361,9 +378,10 @@ void AArch64MachObjectWriter::recordRelocation(
           return;
         }
       }
-      Asm.getContext().reportFatalError(Fixup.getLoc(),
+      Asm.getContext().reportError(Fixup.getLoc(),
                                   "unsupported relocation of variable '" +
                                       Symbol->getName() + "'");
+      return;
     }
   }
 
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
index 2257a208107..fa52c9354c1 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
@@ -395,8 +395,10 @@ unsigned ARMAsmBackend::adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
       Value = -Value;
       isAdd = false;
     }
-    if (Ctx && Value >= 4096)
-      Ctx->reportFatalError(Fixup.getLoc(), "out of range pc-relative fixup value");
+    if (Ctx && Value >= 4096) {
+      Ctx->reportError(Fixup.getLoc(), "out of range pc-relative fixup value");
+      return 0;
+    }
     Value |= isAdd << 23;
 
     // Same addressing mode as fixup_arm_pcrel_10,
@@ -414,8 +416,10 @@ unsigned ARMAsmBackend::adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
       Value = -Value;
       opc = 2; // 0b0010
     }
-    if (Ctx && ARM_AM::getSOImmVal(Value) == -1)
-      Ctx->reportFatalError(Fixup.getLoc(), "out of range pc-relative fixup value");
+    if (Ctx && ARM_AM::getSOImmVal(Value) == -1) {
+      Ctx->reportError(Fixup.getLoc(), "out of range pc-relative fixup value");
+      return 0;
+    }
     // Encode the immediate and shift the opcode into place.
     return ARM_AM::getSOImmVal(Value) | (opc << 21);
   }
@@ -544,8 +548,10 @@ unsigned ARMAsmBackend::adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
     // could have an error on our hands.
     if (Ctx && !STI->getFeatureBits()[ARM::FeatureThumb2] && IsResolved) {
       const char *FixupDiagnostic = reasonForFixupRelaxation(Fixup, Value);
-      if (FixupDiagnostic)
-        Ctx->reportFatalError(Fixup.getLoc(), FixupDiagnostic);
+      if (FixupDiagnostic) {
+        Ctx->reportError(Fixup.getLoc(), FixupDiagnostic);
+        return 0;
+      }
     }
     // Offset by 4, and don't encode the low two bits.
     return ((Value - 4) >> 2) & 0xff;
@@ -559,16 +565,20 @@ unsigned ARMAsmBackend::adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
     // Offset by 4 and don't encode the lower bit, which is always 0.
     if (Ctx && !STI->getFeatureBits()[ARM::FeatureThumb2]) {
       const char *FixupDiagnostic = reasonForFixupRelaxation(Fixup, Value);
-      if (FixupDiagnostic)
-        Ctx->reportFatalError(Fixup.getLoc(), FixupDiagnostic);
+      if (FixupDiagnostic) {
+        Ctx->reportError(Fixup.getLoc(), FixupDiagnostic);
+        return 0;
+      }
     }
     return ((Value - 4) >> 1) & 0x7ff;
   case ARM::fixup_arm_thumb_bcc:
     // Offset by 4 and don't encode the lower bit, which is always 0.
     if (Ctx && !STI->getFeatureBits()[ARM::FeatureThumb2]) {
       const char *FixupDiagnostic = reasonForFixupRelaxation(Fixup, Value);
-      if (FixupDiagnostic)
-        Ctx->reportFatalError(Fixup.getLoc(), FixupDiagnostic);
+      if (FixupDiagnostic) {
+        Ctx->reportError(Fixup.getLoc(), FixupDiagnostic);
+        return 0;
+      }
     }
     return ((Value - 4) >> 1) & 0xff;
   case ARM::fixup_arm_pcrel_10_unscaled: {
@@ -580,8 +590,10 @@ unsigned ARMAsmBackend::adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
       isAdd = false;
     }
     // The value has the low 4 bits encoded in [3:0] and the high 4 in [11:8].
-    if (Ctx && Value >= 256)
-      Ctx->reportFatalError(Fixup.getLoc(), "out of range pc-relative fixup value");
+    if (Ctx && Value >= 256) {
+      Ctx->reportError(Fixup.getLoc(), "out of range pc-relative fixup value");
+      return 0;
+    }
     Value = (Value & 0xf) | ((Value & 0xf0) << 4);
     return Value | (isAdd << 23);
   }
@@ -599,8 +611,10 @@ unsigned ARMAsmBackend::adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
     }
     // These values don't encode the low two bits since they're always zero.
     Value >>= 2;
-    if (Ctx && Value >= 256)
-      Ctx->reportFatalError(Fixup.getLoc(), "out of range pc-relative fixup value");
+    if (Ctx && Value >= 256) {
+      Ctx->reportError(Fixup.getLoc(), "out of range pc-relative fixup value");
+      return 0;
+    }
     Value |= isAdd << 23;
 
     // Same addressing mode as fixup_arm_pcrel_10, but with 16-bit halfwords
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
index bff5df6e3c4..6c8cf7ba14f 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
@@ -509,8 +509,10 @@ public:
   /// necessary.
   void EmitValueImpl(const MCExpr *Value, unsigned Size, SMLoc Loc) override {
     if (const MCSymbolRefExpr *SRE = dyn_cast_or_null<MCSymbolRefExpr>(Value))
-      if (SRE->getKind() == MCSymbolRefExpr::VK_ARM_SBREL && !(Size == 4))
-        getContext().reportFatalError(Loc, "relocated expression must be 32-bit");
+      if (SRE->getKind() == MCSymbolRefExpr::VK_ARM_SBREL && !(Size == 4)) {
+        getContext().reportError(Loc, "relocated expression must be 32-bit");
+        return;
+      }
 
     EmitDataMappingSymbol();
     MCELFStreamer::EmitValueImpl(Value, Size, Loc);
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMMachObjectWriter.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMMachObjectWriter.cpp
index 95d7ea7c04a..cfd504e533a 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMMachObjectWriter.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMMachObjectWriter.cpp
@@ -150,10 +150,12 @@ RecordARMScatteredHalfRelocation(MachObjectWriter *Writer,
   // See <reloc.h>.
   const MCSymbol *A = &Target.getSymA()->getSymbol();
 
-  if (!A->getFragment())
-    Asm.getContext().reportFatalError(Fixup.getLoc(),
+  if (!A->getFragment()) {
+    Asm.getContext().reportError(Fixup.getLoc(),
                        "symbol '" + A->getName() +
                        "' can not be undefined in a subtraction expression");
+    return;
+  }
 
   uint32_t Value = Writer->getSymbolAddress(*A, Layout);
   uint32_t Value2 = 0;
@@ -163,10 +165,12 @@ RecordARMScatteredHalfRelocation(MachObjectWriter *Writer,
   if (const MCSymbolRefExpr *B = Target.getSymB()) {
     const MCSymbol *SB = &B->getSymbol();
 
-    if (!SB->getFragment())
-      Asm.getContext().reportFatalError(Fixup.getLoc(),
+    if (!SB->getFragment()) {
+      Asm.getContext().reportError(Fixup.getLoc(),
                          "symbol '" + B->getSymbol().getName() +
                          "' can not be undefined in a subtraction expression");
+      return;
+    }
 
     // Select the appropriate difference relocation type.
     Type = MachO::ARM_RELOC_HALF_SECTDIFF;
@@ -251,10 +255,12 @@ void ARMMachObjectWriter::RecordARMScatteredRelocation(MachObjectWriter *Writer,
   // See <reloc.h>.
   const MCSymbol *A = &Target.getSymA()->getSymbol();
 
-  if (!A->getFragment())
-    Asm.getContext().reportFatalError(Fixup.getLoc(),
+  if (!A->getFragment()) {
+    Asm.getContext().reportError(Fixup.getLoc(),
                        "symbol '" + A->getName() +
                        "' can not be undefined in a subtraction expression");
+    return;
+  }
 
   uint32_t Value = Writer->getSymbolAddress(*A, Layout);
   uint64_t SecAddr = Writer->getSectionAddress(A->getFragment()->getParent());
@@ -265,10 +271,12 @@ void ARMMachObjectWriter::RecordARMScatteredRelocation(MachObjectWriter *Writer,
     assert(Type == MachO::ARM_RELOC_VANILLA && "invalid reloc for 2 symbols");
     const MCSymbol *SB = &B->getSymbol();
 
-    if (!SB->getFragment())
-      Asm.getContext().reportFatalError(Fixup.getLoc(),
+    if (!SB->getFragment()) {
+      Asm.getContext().reportError(Fixup.getLoc(),
                          "symbol '" + B->getSymbol().getName() +
                          "' can not be undefined in a subtraction expression");
+      return;
+    }
 
     // Select the appropriate difference relocation type.
     Type = MachO::ARM_RELOC_SECTDIFF;
@@ -346,13 +354,15 @@ void ARMMachObjectWriter::recordRelocation(MachObjectWriter *Writer,
   unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
   unsigned Log2Size;
   unsigned RelocType = MachO::ARM_RELOC_VANILLA;
-  if (!getARMFixupKindMachOInfo(Fixup.getKind(), RelocType, Log2Size))
+  if (!getARMFixupKindMachOInfo(Fixup.getKind(), RelocType, Log2Size)) {
     // If we failed to get fixup kind info, it's because there's no legal
     // relocation type for the fixup kind. This happens when it's a fixup that's
     // expected to always be resolvable at assembly time and not have any
     // relocations needed.
-    Asm.getContext().reportFatalError(Fixup.getLoc(),
-                                "unsupported relocation on symbol");
+    Asm.getContext().reportError(Fixup.getLoc(),
+                                 "unsupported relocation on symbol");
+    return;
+  }
 
   // If this is a difference or a defined symbol plus an offset, then we need a
   // scattered relocation entry.  Differences always require scattered
diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp b/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
index a9b31ac877d..e4865e2455e 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
+++ b/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
@@ -63,15 +63,19 @@ static unsigned adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
     // address range. Forcing a signed division because Value can be negative.
     Value = (int64_t)Value / 4;
     // We now check if Value can be encoded as a 16-bit signed immediate.
-    if (!isInt<16>(Value) && Ctx)
-      Ctx->reportFatalError(Fixup.getLoc(), "out of range PC16 fixup");
+    if (!isInt<16>(Value) && Ctx) {
+      Ctx->reportError(Fixup.getLoc(), "out of range PC16 fixup");
+      return 0;
+    }
     break;
   case Mips::fixup_MIPS_PC19_S2:
     // Forcing a signed division because Value can be negative.
     Value = (int64_t)Value / 4;
     // We now check if Value can be encoded as a 19-bit signed immediate.
-    if (!isInt<19>(Value) && Ctx)
-      Ctx->reportFatalError(Fixup.getLoc(), "out of range PC19 fixup");
+    if (!isInt<19>(Value) && Ctx) {
+      Ctx->reportError(Fixup.getLoc(), "out of range PC19 fixup");
+      return 0;
+    }
     break;
   case Mips::fixup_Mips_26:
     // So far we are only using this type for jumps.
@@ -104,45 +108,57 @@ static unsigned adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
     // Forcing a signed division because Value can be negative.
     Value = (int64_t) Value / 2;
     // We now check if Value can be encoded as a 7-bit signed immediate.
-    if (!isInt<7>(Value) && Ctx)
-      Ctx->reportFatalError(Fixup.getLoc(), "out of range PC7 fixup");
+    if (!isInt<7>(Value) && Ctx) {
+      Ctx->reportError(Fixup.getLoc(), "out of range PC7 fixup");
+      return 0;
+    }
     break;
   case Mips::fixup_MICROMIPS_PC10_S1:
     Value -= 2;
     // Forcing a signed division because Value can be negative.
     Value = (int64_t) Value / 2;
     // We now check if Value can be encoded as a 10-bit signed immediate.
-    if (!isInt<10>(Value) && Ctx)
-      Ctx->reportFatalError(Fixup.getLoc(), "out of range PC10 fixup");
+    if (!isInt<10>(Value) && Ctx) {
+      Ctx->reportError(Fixup.getLoc(), "out of range PC10 fixup");
+      return 0;
+    }
     break;
   case Mips::fixup_MICROMIPS_PC16_S1:
     Value -= 4;
     // Forcing a signed division because Value can be negative.
     Value = (int64_t)Value / 2;
     // We now check if Value can be encoded as a 16-bit signed immediate.
-    if (!isInt<16>(Value) && Ctx)
-      Ctx->reportFatalError(Fixup.getLoc(), "out of range PC16 fixup");
+    if (!isInt<16>(Value) && Ctx) {
+      Ctx->reportError(Fixup.getLoc(), "out of range PC16 fixup");
+      return 0;
+    }
     break;
   case Mips::fixup_MIPS_PC18_S3:
     // Forcing a signed division because Value can be negative.
     Value = (int64_t)Value / 8;
     // We now check if Value can be encoded as a 18-bit signed immediate.
-    if (!isInt<18>(Value) && Ctx)
-      Ctx->reportFatalError(Fixup.getLoc(), "out of range PC18 fixup");
+    if (!isInt<18>(Value) && Ctx) {
+      Ctx->reportError(Fixup.getLoc(), "out of range PC18 fixup");
+      return 0;
+    }
     break;
   case Mips::fixup_MIPS_PC21_S2:
     // Forcing a signed division because Value can be negative.
     Value = (int64_t) Value / 4;
     // We now check if Value can be encoded as a 21-bit signed immediate.
-    if (!isInt<21>(Value) && Ctx)
-      Ctx->reportFatalError(Fixup.getLoc(), "out of range PC21 fixup");
+    if (!isInt<21>(Value) && Ctx) {
+      Ctx->reportError(Fixup.getLoc(), "out of range PC21 fixup");
+      return 0;
+    }
     break;
   case Mips::fixup_MIPS_PC26_S2:
     // Forcing a signed division because Value can be negative.
     Value = (int64_t) Value / 4;
     // We now check if Value can be encoded as a 26-bit signed immediate.
-    if (!isInt<26>(Value) && Ctx)
-      Ctx->reportFatalError(Fixup.getLoc(), "out of range PC26 fixup");
+    if (!isInt<26>(Value) && Ctx) {
+      Ctx->reportError(Fixup.getLoc(), "out of range PC26 fixup");
+      return 0;
+    }
     break;
   }
 
diff --git a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMachObjectWriter.cpp b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMachObjectWriter.cpp
index 9d7289658f0..b54a0e1b86b 100644
--- a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMachObjectWriter.cpp
+++ b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMachObjectWriter.cpp
@@ -241,12 +241,12 @@ bool PPCMachObjectWriter::recordScatteredRelocation(
     if (FixupOffset > 0xffffff) {
       char Buffer[32];
       format("0x%x", FixupOffset).print(Buffer, sizeof(Buffer));
-      Asm.getContext().reportFatalError(Fixup.getLoc(),
+      Asm.getContext().reportError(Fixup.getLoc(),
                                   Twine("Section too large, can't encode "
                                         "r_address (") +
                                       Buffer + ") into 24 bits of scattered "
                                                "relocation entry.");
-      llvm_unreachable("fatal error returned?!");
+      return false;
     }
 
     // Is this supposed to follow MCTarget/PPCAsmBackend.cpp:adjustFixupValue()?
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
index 9e801fc8f19..614e4386408 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
@@ -175,9 +175,10 @@ void X86MachObjectWriter::RecordX86_64Relocation(
     // non-relocatable expression.
     if (A->isUndefined() || B->isUndefined()) {
       StringRef Name = A->isUndefined() ? A->getName() : B->getName();
-      Asm.getContext().reportFatalError(Fixup.getLoc(),
+      Asm.getContext().reportError(Fixup.getLoc(),
         "unsupported relocation with subtraction expression, symbol '" +
         Name + "' can not be undefined in a subtraction expression");
+      return;
     }
 
     Value += Writer->getSymbolAddress(*A, Layout) -
@@ -387,12 +388,12 @@ bool X86MachObjectWriter::recordScatteredRelocation(MachObjectWriter *Writer,
     if (FixupOffset > 0xffffff) {
       char Buffer[32];
       format("0x%x", FixupOffset).print(Buffer, sizeof(Buffer));
-      Asm.getContext().reportFatalError(Fixup.getLoc(),
+      Asm.getContext().reportError(Fixup.getLoc(),
                          Twine("Section too large, can't encode "
                                 "r_address (") + Buffer +
                          ") into 24 bits of scattered "
                          "relocation entry.");
-      llvm_unreachable("fatal error returned?!");
+      return false;
     }
 
     MachO::any_relocation_info MRE;