[Object][NFC] Remove unneeded llvm_unreachable

[gAlfonso-bit]

Summary

The structure of this method now matches the one above it.

[MaskRay]

I agree that the call site uses are somewhat problematic, but cast has stronger guarantee. Do you have a test case to trigger a code path that dyn_cast returns nullptr? If not, the if statement should just be replaced with unconditional cast.

llvm/lib/Object/ELFObjectFile.cpp

785–786

This can just used cast and delete llvm_unreachable

[gAlfonso-bit]

This comment was removed by gAlfonso-bit.

[MaskRay]

llvm/utils/TableGen/DecoderEmitter.cpp

2111 ↗

(On Diff #480661)

See the reverted ba59ec2843f99f19d55d7cd9f9ac536fb038fdab: this change seems wrong.

[gAlfonso-bit]

This comment was removed by gAlfonso-bit.

[craig.topper]

llvm/lib/MC/MCExpr.cpp

889

R isn't checked for null after this so if the dynamic cast fails it will dereference a null point. cast would have generated an assert on assertion builds.

[gAlfonso-bit]

This comment was removed by gAlfonso-bit.

[gAlfonso-bit]

This comment was removed by gAlfonso-bit.

[MaskRay]

In D139452#4132950, @gAlfonso-bit wrote:

@MaskRay Can I have commit permissions please

I'll land this patch for you. Your previous changes are all about this kind of NFC cleanup. I think I only want to endorse people with contributions like bug fixing or useful feature requests...

llvm/lib/MC/MCExpr.cpp

case Binary: {
     MCValue LHSValue, RHSValue;
 
     if (!ABE->getLHS()->evaluateAsRelocatableImpl(LHSValue, Asm, Layout, Fixup,
                                                   Addrs, InSet) ||
         !ABE->getRHS()->evaluateAsRelocatableImpl(RHSValue, Asm, Layout, Fixup,
                                                   Addrs, InSet)) {
       // Check if both are Target Expressions, see if we can compare them.
       if (const MCTargetExpr *L = dyn_cast<MCTargetExpr>(ABE->getLHS())) {
-        const MCTargetExpr *R = cast<MCTargetExpr>(ABE->getRHS());
+        const MCTargetExpr *R = dyn_cast<MCTargetExpr>(ABE->getRHS());
         switch (ABE->getOpcode()) {
         case MCBinaryExpr::EQ:
           Res = MCValue::get(L->isEqualTo(R) ? -1 : 0);
           return true;
         case MCBinaryExpr::NE:
           Res = MCValue::get(R->isEqualTo(R) ? 0 : -1);
           return true;
         default:

llvm/lib/Object/ELFObjectFile.cpp

 
 Expected<std::vector<BBAddrMap>> ELFObjectFileBase::readBBAddrMap(
     std::optional<unsigned> TextSectionIndex) const {
   if (const auto *Obj = dyn_cast<ELF32LEObjectFile>(this))
     return readBBAddrMapImpl(Obj->getELFFile(), TextSectionIndex);
   if (const auto *Obj = dyn_cast<ELF64LEObjectFile>(this))
     return readBBAddrMapImpl(Obj->getELFFile(), TextSectionIndex);
   if (const auto *Obj = dyn_cast<ELF32BEObjectFile>(this))
     return readBBAddrMapImpl(Obj->getELFFile(), TextSectionIndex);
-  if (const auto *Obj = cast<ELF64BEObjectFile>(this))
-    return readBBAddrMapImpl(Obj->getELFFile(), TextSectionIndex);
-  else
-    llvm_unreachable("Unsupported binary format");
+  return readBBAddrMapImpl(cast<ELF64BEObjectFile>(this)->getELFFile(),
+                           TextSectionIndex);
 }