Fix address computation for headers.

If the linker script has SECTIONS, the address computation is now
always done in LinkerScript::assignAddresses, like for any other
section.

Before fixHeaders would do a tentative computation that
assignAddresses would sometimes override.

This patch also splits the cases where assignAddresses needs to add
the headers to the first PT_LOAD and the address computation. The net
effect is that we no longer create an empty page for no reason in the
included test case, which matches bfd behavior.

llvm-svn: 287565
diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index 38477c8..cdc6695 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -707,24 +707,21 @@
   if (FirstPTLoad == Phdrs.end())
     return;
 
-  if (HeaderSize <= MinVA) {
-    // If linker script specifies program headers and first PT_LOAD doesn't
-    // have both PHDRS and FILEHDR attributes then do nothing
-    if (!Opt.PhdrsCommands.empty()) {
-      size_t SegNum = std::distance(Phdrs.begin(), FirstPTLoad);
-      if (!Opt.PhdrsCommands[SegNum].HasPhdrs ||
-          !Opt.PhdrsCommands[SegNum].HasFilehdr)
-        return;
-    }
-    // ELF and Program headers need to be right before the first section in
-    // memory. Set their addresses accordingly.
-    MinVA = alignDown(MinVA - HeaderSize, Target->PageSize);
-    Out<ELFT>::ElfHeader->Addr = MinVA;
-    Out<ELFT>::ProgramHeaders->Addr = Out<ELFT>::ElfHeader->Size + MinVA;
+  // If the linker script doesn't have PHDRS, add ElfHeader and ProgramHeaders
+  // now that we know we have space.
+  if (HeaderSize <= MinVA && !hasPhdrsCommands()) {
     FirstPTLoad->First = Out<ELFT>::ElfHeader;
     if (!FirstPTLoad->Last)
       FirstPTLoad->Last = Out<ELFT>::ProgramHeaders;
-  } else if (!FirstPTLoad->First) {
+  }
+
+  // ELF and Program headers need to be right before the first section in
+  // memory. Set their addresses accordingly.
+  MinVA = alignDown(MinVA - HeaderSize, Target->PageSize);
+  Out<ELFT>::ElfHeader->Addr = MinVA;
+  Out<ELFT>::ProgramHeaders->Addr = Out<ELFT>::ElfHeader->Size + MinVA;
+
+  if (!FirstPTLoad->First) {
     // Sometimes the very first PT_LOAD segment can be empty.
     // This happens if (all conditions met):
     //  - Linker script is used
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index a5d34b5..13ddf61 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -1267,11 +1267,13 @@
 // sections. These are special, we do not include them into output sections
 // list, but have them to simplify the code.
 template <class ELFT> void Writer<ELFT>::fixHeaders() {
-  uintX_t BaseVA = ScriptConfig->HasSections ? 0 : Config->ImageBase;
-  Out<ELFT>::ElfHeader->Addr = BaseVA;
-  uintX_t Off = Out<ELFT>::ElfHeader->Size;
-  Out<ELFT>::ProgramHeaders->Addr = Off + BaseVA;
   Out<ELFT>::ProgramHeaders->Size = sizeof(Elf_Phdr) * Phdrs.size();
+  // If the script has SECTIONS, assignAddresses will compute the values.
+  if (ScriptConfig->HasSections)
+    return;
+  uintX_t BaseVA = Config->ImageBase;
+  Out<ELFT>::ElfHeader->Addr = BaseVA;
+  Out<ELFT>::ProgramHeaders->Addr = BaseVA + Out<ELFT>::ElfHeader->Size;
 }
 
 // Assign VAs (addresses at run-time) to output sections.