[lld] r259474 - ELF: Simplify and add comments.

[Rui Ueyama via llvm-commits]

Author: ruiu
Date: Tue Feb  2 01:50:18 2016
New Revision: 259474

URL: http://llvm.org/viewvc/llvm-project?rev=259474&view=rev
Log:
ELF: Simplify and add comments.

Modified:
    lld/trunk/ELF/Writer.cpp

Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=259474&r1=259473&r2=259474&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Tue Feb  2 01:50:18 2016
@@ -387,15 +387,23 @@ void Writer<ELFT>::scanRelocs(
         continue;
     }
 
-    // Here we are creating a relocation for the dynamic linker based on
-    // a relocation from an object file, but some relocations need no
-    // load-time fixup when the final target is known. Skip such relocation.
-    bool CBP = canBePreempted(Body, /*NeedsGot=*/false);
-    bool Dynrel = Config->Shared && !Target->isRelRelative(Type) &&
-                  !Target->isSizeRel(Type);
-    if (CBP)
+    // We get here if a program was not compiled as PIC.
+    if (canBePreempted(Body, /*NeedsGot=*/false)) {
       Body->setUsedInDynamicReloc();
-    if (CBP || Dynrel)
+      Out<ELFT>::RelaDyn->addReloc({&C, &RI});
+      continue;
+    }
+
+    // If we get here, the code we are handling is not PIC. We need to copy
+    // relocations from object files to the output file, so that the
+    // dynamic linker can fix up addresses. But there are a few exceptions.
+    // If the relocation will not change at runtime, we don't need to copy
+    // them. For example, we don't copy PC-relative relocations because
+    // the distance between two symbols won't change whereever they are
+    // loaded. Likewise, if we are linking an executable, it will be loaded
+    // at a fixed address, so we don't copy relocations.
+    if (Config->Shared && !Target->isRelRelative(Type) &&
+        !Target->isSizeRel(Type))
       Out<ELFT>::RelaDyn->addReloc({&C, &RI});
   }
 }