[Mips] Handle one byte unsupported relocations

[smaksimovic]

Summary

Fail gracefully instead of crashing upon encountering
this type of relocation.

[sdardis]

Two additional nits to the ones inlined, rather that use the term 'illegal' say 'unsupported', this goes for the title as well as the test file name.

Also, the summary should be "Fail gracefully" rather than "Exit gracefully".

Otherwise LGTM.

lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp

229

Nit: Mips does not support one byte fixups -> MIPS does not support one byte relocations

test/MC/Mips/illegal-relocation.s

3 ↗

(On Diff #129052)

Nit: description.

lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp

unsigned MipsELFObjectWriter::getRelocType(MCContext &Ctx,
                                            const MCFixup &Fixup,
                                            bool IsPCRel) const {
   // Determine the type of the relocation.
   unsigned Kind = (unsigned)Fixup.getKind();
 
   switch (Kind) {
   case Mips::fixup_Mips_NONE:
     return ELF::R_MIPS_NONE;
+  case FK_Data_1:
+    report_fatal_error("MIPS does not support one byte relocations");
   case Mips::fixup_Mips_16:
   case FK_Data_2:
     return IsPCRel ? ELF::R_MIPS_PC16 : ELF::R_MIPS_16;
   case Mips::fixup_Mips_32:
   case FK_Data_4:
     return IsPCRel ? ELF::R_MIPS_PC32 : ELF::R_MIPS_32;
   }
 

test/MC/Mips/unsupported-relocation.s

+# RUN: not llvm-mc -triple mips-unknown-linux -filetype=obj %s 2>%t
+# RUN: FileCheck %s < %t
+
+# Check that we emit an error for unsupported relocations instead of crashing.
+
+        .globl x
+
+        .data
+foo:
+        .byte   x
+        .byte   x+1
+
+# CHECK: LLVM ERROR: MIPS does not support one byte relocations