[lld] r345154 - Refactor assignFileOffsets. NFC.

[Rui Ueyama via llvm-commits]

Author: ruiu
Date: Wed Oct 24 08:47:46 2018
New Revision: 345154

URL: http://llvm.org/viewvc/llvm-project?rev=345154&view=rev
Log:
Refactor assignFileOffsets. NFC.

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=345154&r1=345153&r2=345154&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Wed Oct 24 08:47:46 2018
@@ -2020,49 +2020,48 @@ template <class ELFT> void Writer<ELFT>:
   }
 }
 
-// Adjusts the file alignment for a given output section and returns
-// its new file offset. The file offset must be the same with its
-// virtual address (modulo the page size) so that the loader can load
-// executables without any address adjustment.
-static uint64_t getFileAlignment(uint64_t Off, OutputSection *Cmd) {
-  OutputSection *First = Cmd->PtLoad ? Cmd->PtLoad->FirstSec : nullptr;
-  // The first section in a PT_LOAD has to have congruent offset and address
-  // module the page size.
-  if (Cmd == First)
-    return alignTo(Off, std::max<uint64_t>(Cmd->Alignment, Config->MaxPageSize),
-                   Cmd->Addr);
-
-  // For SHT_NOBITS we don't want the alignment of the section to impact the
-  // offset of the sections that follow. Since nothing seems to care about the
-  // sh_offset of the SHT_NOBITS section itself, just ignore it.
-  if (Cmd->Type == SHT_NOBITS)
+// Compute an in-file position for a given section. The file offset must be the
+// same with its virtual address modulo the page size, so that the loader can
+// load executables without any address adjustment.
+static uint64_t computeFileOffset(OutputSection *OS, uint64_t Off) {
+  // File offsets are not significant for .bss sections. By convention, we keep
+  // section offsets monotonically increasing rather than setting to zero.
+  if (OS->Type == SHT_NOBITS)
     return Off;
 
   // If the section is not in a PT_LOAD, we just have to align it.
-  if (!Cmd->PtLoad)
-    return alignTo(Off, Cmd->Alignment);
+  if (!OS->PtLoad)
+    return alignTo(Off, OS->Alignment);
+
+  // The first section in a PT_LOAD has to have congruent offset and address
+  // module the page size.
+  OutputSection *First = OS->PtLoad->FirstSec;
+  if (OS == First) {
+    uint64_t Alignment = std::max<uint64_t>(OS->Alignment, Config->MaxPageSize);
+    return alignTo(Off, Alignment, OS->Addr);
+  }
 
   // If two sections share the same PT_LOAD the file offset is calculated
   // using this formula: Off2 = Off1 + (VA2 - VA1).
-  return First->Offset + Cmd->Addr - First->Addr;
+  return First->Offset + OS->Addr - First->Addr;
 }
 
-static uint64_t setOffset(OutputSection *Cmd, uint64_t Off) {
-  Off = getFileAlignment(Off, Cmd);
-  Cmd->Offset = Off;
+// Set an in-file position to a given section and returns the end position of
+// the section.
+static uint64_t setFileOffset(OutputSection *OS, uint64_t Off) {
+  Off = computeFileOffset(OS, Off);
+  OS->Offset = Off;
 
-  // For SHT_NOBITS we should not count the size.
-  if (Cmd->Type == SHT_NOBITS)
+  if (OS->Type == SHT_NOBITS)
     return Off;
-
-  return Off + Cmd->Size;
+  return Off + OS->Size;
 }
 
 template <class ELFT> void Writer<ELFT>::assignFileOffsetsBinary() {
   uint64_t Off = 0;
   for (OutputSection *Sec : OutputSections)
     if (Sec->Flags & SHF_ALLOC)
-      Off = setOffset(Sec, Off);
+      Off = setFileOffset(Sec, Off);
   FileSize = alignTo(Off, Config->Wordsize);
 }
 
@@ -2073,8 +2072,8 @@ static std::string rangeToString(uint64_
 // Assign file offsets to output sections.
 template <class ELFT> void Writer<ELFT>::assignFileOffsets() {
   uint64_t Off = 0;
-  Off = setOffset(Out::ElfHeader, Off);
-  Off = setOffset(Out::ProgramHeaders, Off);
+  Off = setFileOffset(Out::ElfHeader, Off);
+  Off = setFileOffset(Out::ProgramHeaders, Off);
 
   PhdrEntry *LastRX = nullptr;
   for (PhdrEntry *P : Phdrs)
@@ -2082,7 +2081,7 @@ template <class ELFT> void Writer<ELFT>:
       LastRX = P;
 
   for (OutputSection *Sec : OutputSections) {
-    Off = setOffset(Sec, Off);
+    Off = setFileOffset(Sec, Off);
     if (Script->HasSectionsCommand)
       continue;
     // If this is a last section of the last executable segment and that