Reduce number of getOffset calls.

[ruiu]

Summary

Mergeable sections usually don't have relocations, so this piece
of code is being used to skip dead EH frames. This patch make it
explicit so that we don't needlessly spend time on getOffset.

[• rafael]

Unfortunately benchmarking this I got only very small variations. See
attached file for details.

Cheers,
Rafael

• times678 BDownload

ELF/Relocations.cpp

for (auto I = Rels.begin(), E = Rels.end(); I != E; ++I) {
 
     RelExpr Expr = Target->getRelExpr(Type, Body);
     bool Preemptible = isPreemptible(Body, Type);
     Expr = adjustExpr(File, Body, IsWrite, Expr, Type, Buf + RI.r_offset);
     if (HasError)
       continue;
 
     // Skip a relocation that points to a dead piece
-    // in a mergeable section.
-    if (C.getOffset(RI.r_offset) == (uintX_t)-1)
+    // in an .eh_frame section.
+    if (isa<EhInputSection<ELFT>>(&C) &&
+        C.getOffset(RI.r_offset) == (uintX_t)-1)
       continue;
 
     // This relocation does not require got entry, but it is relative to got and
     // needs it to be created. Here we request for that.
     if (Expr == R_GOTONLY_PC || Expr == R_GOTREL || Expr == R_PPC_TOC)
       Out<ELFT>::Got->HasGotOffRel = true;
 
     uintX_t Addend = computeAddend(File, Buf, E, RI, Expr, Body);