[RISCV] Don't crash on unsupported relocations

[luismarques]

Summary

Instead of crashing due to the llvm_unreachable, provide a proper error when invalid fixups/relocs are encountered.

[asb]

Please update the check so it checks the error location too, like we do for other *invalid.s checks.

[luismarques]

Update test CHECKs to check for line number/columns.

[luismarques]

Add RUN line for riscv64

[asb]

LGTM, thanks.

llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFObjectWriter.cpp

 //===-- RISCVELFObjectWriter.cpp - RISCV ELF Writer -----------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "MCTargetDesc/RISCVFixupKinds.h"
 #include "MCTargetDesc/RISCVMCExpr.h"
 #include "MCTargetDesc/RISCVMCTargetDesc.h"
+#include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCELFObjectWriter.h"
 #include "llvm/MC/MCFixup.h"
 #include "llvm/MC/MCObjectWriter.h"
 #include "llvm/Support/ErrorHandling.h"
 
 using namespace llvm;
 
 namespace {
unsigned RISCVELFObjectWriter::getRelocType(MCContext &Ctx,
                                             const MCFixup &Fixup,
                                             bool IsPCRel) const {
   const MCExpr *Expr = Fixup.getValue();
   // Determine the type of the relocation
   unsigned Kind = Fixup.getTargetKind();
   if (IsPCRel) {
     switch (Kind) {
     default:
-      llvm_unreachable("invalid fixup kind!");
+      Ctx.reportError(Fixup.getLoc(), "Unsupported relocation type");
+      return ELF::R_RISCV_NONE;
     case FK_Data_4:
     case FK_PCRel_4:
       return ELF::R_RISCV_32_PCREL;
     case RISCV::fixup_riscv_pcrel_hi20:
       return ELF::R_RISCV_PCREL_HI20;
     case RISCV::fixup_riscv_pcrel_lo12_i:
       return ELF::R_RISCV_PCREL_LO12_I;
     case RISCV::fixup_riscv_pcrel_lo12_s:
case RISCV::fixup_riscv_call:
       return ELF::R_RISCV_CALL;
     case RISCV::fixup_riscv_call_plt:
       return ELF::R_RISCV_CALL_PLT;
     }
   }
 
   switch (Kind) {
   default:
-    llvm_unreachable("invalid fixup kind!");
+    Ctx.reportError(Fixup.getLoc(), "Unsupported relocation type");
+    return ELF::R_RISCV_NONE;
+  case FK_Data_1:
+    Ctx.reportError(Fixup.getLoc(), "1-byte data relocations not supported");
+    return ELF::R_RISCV_NONE;
+  case FK_Data_2:
+    Ctx.reportError(Fixup.getLoc(), "2-byte data relocations not supported");
+    return ELF::R_RISCV_NONE;
   case FK_Data_4:
     if (Expr->getKind() == MCExpr::Target &&
         cast<RISCVMCExpr>(Expr)->getKind() == RISCVMCExpr::VK_RISCV_32_PCREL)
       return ELF::R_RISCV_32_PCREL;
     return ELF::R_RISCV_32;
   case FK_Data_8:
     return ELF::R_RISCV_64;
   case FK_Data_Add_1:

llvm/test/MC/RISCV/fixups-invalid.s

+# RUN: not llvm-mc -filetype=obj %s -triple=riscv32 -o /dev/null 2>&1 \
+# RUN:     | FileCheck %s
+
+.byte foo
+# CHECK: error: 1-byte data relocations not supported
+# CHECK-NEXT: foo
+
+.2byte bar
+# CHECK: error: 2-byte data relocations not supported
+# CHECK-NEXT: bar