[LLD][COFF][NFC] Use dyn_cast on section chunks

Instead of dyn_cast_or_null, chunk pointers are never null.

Author: cjacek

lld/COFF/Writer.cpp

@@ -472,7 +472,7 @@ bool Writer::createThunks(OutputSection *os, int margin) {
   // Recheck Chunks.size() each iteration, since we can insert more
   // elements into it.
   for (size_t i = 0; i != os->chunks.size(); ++i) {
-    SectionChunk *sc = dyn_cast_or_null<SectionChunk>(os->chunks[i]);
+    SectionChunk *sc = dyn_cast<SectionChunk>(os->chunks[i]);
     if (!sc)
       continue;
     MachineTypes machine = sc->getMachine();
@@ -606,7 +606,7 @@ void Writer::createECCodeMap() {
 // Verify that all relocations are in range, with no extra margin requirements.
 bool Writer::verifyRanges(const std::vector<Chunk *> chunks) {
   for (Chunk *c : chunks) {
-    SectionChunk *sc = dyn_cast_or_null<SectionChunk>(c);
+    SectionChunk *sc = dyn_cast<SectionChunk>(c);
     if (!sc)
       continue;
     MachineTypes machine = sc->getMachine();
@@ -872,8 +872,8 @@ bool Writer::fixGnuImportChunks() {
     if (!pSec->chunks.empty())
       hasIdata = true;
     llvm::stable_sort(pSec->chunks, [&](Chunk *s, Chunk *t) {
-      SectionChunk *sc1 = dyn_cast_or_null<SectionChunk>(s);
-      SectionChunk *sc2 = dyn_cast_or_null<SectionChunk>(t);
+      SectionChunk *sc1 = dyn_cast<SectionChunk>(s);
+      SectionChunk *sc2 = dyn_cast<SectionChunk>(t);
       if (!sc1 || !sc2) {
         // if SC1, order them ascending. If SC2 or both null,
         // S is not less than T.