[ELF] Fix GCC8 warnings about "fall through", NFCI

Add break statements in Object/ELF.cpp since the code should consider the
generic tags for Hexagon, MIPS, and PPC. Add a test (copied from llvm-readobj)
to show that this works correctly (earlier versions of this patch would have
asserted).

The warnings in X86ELFObjectWriter.cpp are actually false-positives since
the nested switch() handles all possible values and returns in all cases.
Make this explicit by adding llvm_unreachable's.

Differential Revision: https://reviews.llvm.org/D58837

llvm-svn: 356037

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
index 910a9fcc3c3..8b6262ec22f 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
@@ -113,6 +113,7 @@ static unsigned getRelocType64(MCContext &Ctx, SMLoc Loc,
     case RT64_8:
       return IsPCRel ? ELF::R_X86_64_PC8 : ELF::R_X86_64_8;
     }
+    llvm_unreachable("unexpected relocation type!");
   case MCSymbolRefExpr::VK_GOT:
     switch (Type) {
     case RT64_64:
@@ -124,6 +125,7 @@ static unsigned getRelocType64(MCContext &Ctx, SMLoc Loc,
     case RT64_8:
       llvm_unreachable("Unimplemented");
     }
+    llvm_unreachable("unexpected relocation type!");
   case MCSymbolRefExpr::VK_GOTOFF:
     assert(Type == RT64_64);
     assert(!IsPCRel);
@@ -140,6 +142,7 @@ static unsigned getRelocType64(MCContext &Ctx, SMLoc Loc,
     case RT64_8:
       llvm_unreachable("Unimplemented");
     }
+    llvm_unreachable("unexpected relocation type!");
   case MCSymbolRefExpr::VK_DTPOFF:
     assert(!IsPCRel);
     switch (Type) {
@@ -152,6 +155,7 @@ static unsigned getRelocType64(MCContext &Ctx, SMLoc Loc,
     case RT64_8:
       llvm_unreachable("Unimplemented");
     }
+    llvm_unreachable("unexpected relocation type!");
   case MCSymbolRefExpr::VK_SIZE:
     assert(!IsPCRel);
     switch (Type) {
@@ -164,6 +168,7 @@ static unsigned getRelocType64(MCContext &Ctx, SMLoc Loc,
     case RT64_8:
       llvm_unreachable("Unimplemented");
     }
+    llvm_unreachable("unexpected relocation type!");
   case MCSymbolRefExpr::VK_TLSCALL:
     return ELF::R_X86_64_TLSDESC_CALL;
   case MCSymbolRefExpr::VK_TLSDESC:
@@ -196,6 +201,7 @@ static unsigned getRelocType64(MCContext &Ctx, SMLoc Loc,
     case X86::reloc_riprel_4byte_movq_load:
       return ELF::R_X86_64_REX_GOTPCRELX;
     }
+    llvm_unreachable("unexpected relocation type!");
   }
 }
 
@@ -233,6 +239,7 @@ static unsigned getRelocType32(MCContext &Ctx,
     case RT32_8:
       return IsPCRel ? ELF::R_386_PC8 : ELF::R_386_8;
     }
+    llvm_unreachable("unexpected relocation type!");
   case MCSymbolRefExpr::VK_GOT:
     assert(Type == RT32_32);
     if (IsPCRel)