Remove doesSectionRequireSymbols.

In an assembly expression like

bar:
.long L0 + 1

the intended semantics is that bar will contain a pointer one byte past L0.

In sections that are merged by content (strings, 4 byte constants, etc), a
single position in the section doesn't give the linker enough information.
For example, it would not be able to tell a relocation must point to the
end of a string, since that would look just like the start of the next.

The solution used in ELF to use relocation with symbols if there is a non-zero
addend.

In MachO before this patch we would just keep all symbols in some sections.

This would miss some cases (only cstrings on x86_64 were implemented) and was
inefficient since most relocations have an addend of 0 and can be represented
without the symbol.

This patch implements the non-zero addend logic for MachO too.

llvm-svn: 224985

1 files changed, 23 insertions, 27 deletions

diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp
index e12a24be0a6..2ea3826e471 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp
@@ -10,6 +10,7 @@
 #include "MCTargetDesc/AArch64FixupKinds.h"
 #include "MCTargetDesc/AArch64MCTargetDesc.h"
 #include "llvm/ADT/Twine.h"
+#include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCAsmLayout.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCContext.h"
@@ -33,7 +34,7 @@ public:
       : MCMachObjectTargetWriter(true /* is64Bit */, CPUType, CPUSubtype,
                                  /*UseAggressiveSymbolFolding=*/true) {}
 
-  void RecordRelocation(MachObjectWriter *Writer, const MCAssembler &Asm,
+  void RecordRelocation(MachObjectWriter *Writer, MCAssembler &Asm,
                         const MCAsmLayout &Layout, const MCFragment *Fragment,
                         const MCFixup &Fixup, MCValue Target,
                         uint64_t &FixedValue) override;
@@ -113,7 +114,7 @@ bool AArch64MachObjectWriter::getAArch64FixupKindMachOInfo(
 }
 
 void AArch64MachObjectWriter::RecordRelocation(
-    MachObjectWriter *Writer, const MCAssembler &Asm, const MCAsmLayout &Layout,
+    MachObjectWriter *Writer, MCAssembler &Asm, const MCAsmLayout &Layout,
     const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target,
     uint64_t &FixedValue) {
   unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
@@ -123,9 +124,9 @@ void AArch64MachObjectWriter::RecordRelocation(
   unsigned Log2Size = 0;
   int64_t Value = 0;
   unsigned Index = 0;
-  unsigned IsExtern = 0;
   unsigned Type = 0;
   unsigned Kind = Fixup.getKind();
+  const MCSymbolData *RelSymbol = nullptr;
 
   FixupOffset += Fixup.getOffset();
 
@@ -171,10 +172,8 @@ void AArch64MachObjectWriter::RecordRelocation(
     // FIXME: Should this always be extern?
     // SymbolNum of 0 indicates the absolute section.
     Type = MachO::ARM64_RELOC_UNSIGNED;
-    Index = 0;
 
     if (IsPCRel) {
-      IsExtern = 1;
       Asm.getContext().FatalError(Fixup.getLoc(),
                                   "PC relative absolute relocation!");
 
@@ -198,15 +197,12 @@ void AArch64MachObjectWriter::RecordRelocation(
         Layout.getSymbolOffset(&B_SD) ==
             Layout.getFragmentOffset(Fragment) + Fixup.getOffset()) {
       // SymB is the PC, so use a PC-rel pointer-to-GOT relocation.
-      Index = A_Base->getIndex();
-      IsExtern = 1;
       Type = MachO::ARM64_RELOC_POINTER_TO_GOT;
       IsPCRel = 1;
       MachO::any_relocation_info MRE;
       MRE.r_word0 = FixupOffset;
-      MRE.r_word1 = ((Index << 0) | (IsPCRel << 24) | (Log2Size << 25) |
-                     (IsExtern << 27) | (Type << 28));
-      Writer->addRelocation(Fragment->getParent(), MRE);
+      MRE.r_word1 = (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
+      Writer->addRelocation(A_Base, Fragment->getParent(), MRE);
       return;
     } else if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None ||
                Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None)
@@ -252,21 +248,23 @@ void AArch64MachObjectWriter::RecordRelocation(
                   ? 0
                   : Writer->getSymbolAddress(B_Base, Layout));
 
-    Index = A_Base->getIndex();
-    IsExtern = 1;
     Type = MachO::ARM64_RELOC_UNSIGNED;
 
     MachO::any_relocation_info MRE;
     MRE.r_word0 = FixupOffset;
-    MRE.r_word1 = ((Index << 0) | (IsPCRel << 24) | (Log2Size << 25) |
-                   (IsExtern << 27) | (Type << 28));
-    Writer->addRelocation(Fragment->getParent(), MRE);
+    MRE.r_word1 = (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
+    Writer->addRelocation(A_Base, Fragment->getParent(), MRE);
 
-    Index = B_Base->getIndex();
-    IsExtern = 1;
+    RelSymbol = B_Base;
     Type = MachO::ARM64_RELOC_SUBTRACTOR;
   } else { // A + constant
     const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
+    if (Symbol->isTemporary() && Value) {
+      const MCSection &Sec = Symbol->getSection();
+      if (!Asm.getContext().getAsmInfo()->isSectionAtomizableBySymbols(Sec))
+        Asm.addLocalUsedInReloc(*Symbol);
+    }
+
     const MCSymbolData &SD = Asm.getSymbolData(*Symbol);
     const MCSymbolData *Base = Asm.getAtom(&SD);
     const MCSectionMachO &Section = static_cast<const MCSectionMachO &>(
@@ -310,8 +308,7 @@ void AArch64MachObjectWriter::RecordRelocation(
     // sections, and for pointer-sized relocations (.quad), we allow section
     // relocations.  It's code sections that run into trouble.
     if (Base) {
-      Index = Base->getIndex();
-      IsExtern = 1;
+      RelSymbol = Base;
 
       // Add the local offset, if needed.
       if (Base != &SD)
@@ -329,7 +326,6 @@ void AArch64MachObjectWriter::RecordRelocation(
       const MCSectionData &SymSD =
           Asm.getSectionData(SD.getSymbol().getSection());
       Index = SymSD.getOrdinal() + 1;
-      IsExtern = 0;
       Value += Writer->getSymbolAddress(&SD, Layout);
 
       if (IsPCRel)
@@ -362,16 +358,16 @@ void AArch64MachObjectWriter::RecordRelocation(
 
     MachO::any_relocation_info MRE;
     MRE.r_word0 = FixupOffset;
-    MRE.r_word1 = ((Index << 0) | (IsPCRel << 24) | (Log2Size << 25) |
-                   (IsExtern << 27) | (Type << 28));
-    Writer->addRelocation(Fragment->getParent(), MRE);
+    MRE.r_word1 =
+        (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
+    Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
 
     // Now set up the Addend relocation.
     Type = MachO::ARM64_RELOC_ADDEND;
     Index = Value;
+    RelSymbol = nullptr;
     IsPCRel = 0;
     Log2Size = 2;
-    IsExtern = 0;
 
     // Put zero into the instruction itself. The addend is in the relocation.
     Value = 0;
@@ -383,9 +379,9 @@ void AArch64MachObjectWriter::RecordRelocation(
   // struct relocation_info (8 bytes)
   MachO::any_relocation_info MRE;
   MRE.r_word0 = FixupOffset;
-  MRE.r_word1 = ((Index << 0) | (IsPCRel << 24) | (Log2Size << 25) |
-                 (IsExtern << 27) | (Type << 28));
-  Writer->addRelocation(Fragment->getParent(), MRE);
+  MRE.r_word1 =
+      (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
+  Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
 }
 
 MCObjectWriter *llvm::createAArch64MachObjectWriter(raw_ostream &OS,