Sorry for such a large commit. The summary is that only MachO cares about the

actuall addresses in a .o file, so it is better to let the MachO writer compute
it.

This is good for two reasons. First, areas that shouldn't care about
addresses now don't have access to it. Second, the layout of each section
is independent. I should use this in a subsequent commit to speed it up.

Most of the patch is just removing the section address computation. The two
interesting parts are the change on how we handle padding in the end
of sections and how MachO can get the address of a-b when a and b are in
different sections.

Since now the expression evaluation normally doesn't know the section address,
it will think that a-b needs relocation and let the MachO writer know. Once
it has computed the section addresses, it calls back the expression evaluation
with the section addresses to resolve these expressions.

The remaining problem is the handling of padding. Currently it will create
a special alignment fragment at the end. Since that fragment doesn't update
the alignment of the section, it needs the real address to be computed.

Since now the layout will not compute a-b with a and b in different sections,
the only effect that the special alignment fragment has is update the
address size of the section. This can also be done by the MachO writer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121076 91177308-0d34-0410-b5e6-96231b3b80d8

5 files changed, 13 insertions, 46 deletions

diff --git a/include/llvm/MC/MCAsmLayout.h b/include/llvm/MC/MCAsmLayout.h
index ce9692dcaf..805af6257f 100644
--- a/include/llvm/MC/MCAsmLayout.h
+++ b/include/llvm/MC/MCAsmLayout.h
@@ -66,11 +66,6 @@ public:
   /// been initialized.
   void LayoutFragment(MCFragment *Fragment);
 
-  /// \brief Performs initial layout for a single section, assuming that the
-  /// previous section (including its fragments) has already been layed out
-  /// correctly.
-  void LayoutSection(MCSectionData *SD);
-
   /// @name Section Access (in layout order)
   /// @{
 
@@ -93,20 +88,9 @@ public:
   uint64_t getFragmentOffset(const MCFragment *F) const;
 
   /// @}
-  /// @name Section Layout Data
-  /// @{
-
-  /// \brief Get the computed address of the given section.
-  uint64_t getSectionAddress(const MCSectionData *SD) const;
-
-  /// @}
   /// @name Utility Functions
   /// @{
 
-  /// \brief Get the address of the given fragment, as computed in the current
-  /// layout.
-  uint64_t getFragmentAddress(const MCFragment *F) const;
-
   /// \brief Get the address space size of the given section, as it effects
   /// layout. This may differ from the size reported by \see getSectionSize() by
   /// not including section tail padding.
@@ -116,13 +100,6 @@ public:
   /// file. This may include additional padding, or be 0 for virtual sections.
   uint64_t getSectionFileSize(const MCSectionData *SD) const;
 
-  /// \brief Get the logical data size of the given section.
-  uint64_t getSectionSize(const MCSectionData *SD) const;
-
-  /// \brief Get the address of the given symbol, as computed in the current
-  /// layout.
-  uint64_t getSymbolAddress(const MCSymbolData *SD) const;
-
   /// \brief Get the offset of the given symbol, as computed in the current
   /// layout.
   uint64_t getSymbolOffset(const MCSymbolData *SD) const;
diff --git a/include/llvm/MC/MCAssembler.h b/include/llvm/MC/MCAssembler.h
index ba89436981..8a5009ffc4 100644
--- a/include/llvm/MC/MCAssembler.h
+++ b/include/llvm/MC/MCAssembler.h
@@ -236,19 +236,12 @@ class MCAlignFragment : public MCFragment {
   /// target dependent.
   bool EmitNops : 1;
 
-  /// OnlyAlignAddress - Flag to indicate that this align is only used to adjust
-  /// the address space size of a section and that it should not be included as
-  /// part of the section size. This flag can only be used on the last fragment
-  /// in a section.
-  bool OnlyAlignAddress : 1;
-
 public:
   MCAlignFragment(unsigned _Alignment, int64_t _Value, unsigned _ValueSize,
                   unsigned _MaxBytesToEmit, MCSectionData *SD = 0)
     : MCFragment(FT_Align, SD), Alignment(_Alignment),
       Value(_Value),ValueSize(_ValueSize),
-      MaxBytesToEmit(_MaxBytesToEmit), EmitNops(false),
-      OnlyAlignAddress(false) {}
+      MaxBytesToEmit(_MaxBytesToEmit), EmitNops(false) {}
 
   /// @name Accessors
   /// @{
@@ -264,9 +257,6 @@ public:
   bool hasEmitNops() const { return EmitNops; }
   void setEmitNops(bool Value) { EmitNops = Value; }
 
-  bool hasOnlyAlignAddress() const { return OnlyAlignAddress; }
-  void setOnlyAlignAddress(bool Value) { OnlyAlignAddress = Value; }
-
   /// @}
 
   static bool classof(const MCFragment *F) {
@@ -447,10 +437,6 @@ private:
   //
   // FIXME: This could all be kept private to the assembler implementation.
 
-  /// Address - The computed address of this section. This is ~0 until
-  /// initialized.
-  uint64_t Address;
-
   /// HasInstructions - Whether this section has had instructions emitted into
   /// it.
   unsigned HasInstructions : 1;
@@ -679,7 +665,6 @@ private:
 
   unsigned RelaxAll : 1;
   unsigned SubsectionsViaSymbols : 1;
-  unsigned PadSectionToAlignment : 1;
 
 private:
   /// Evaluate a fixup to a relocatable expression and the value which should be
@@ -713,7 +698,6 @@ private:
   /// Compute the effective fragment size assuming it is layed out at the given
   /// \arg SectionAddress and \arg FragmentOffset.
   uint64_t ComputeFragmentSize(const MCFragment &F,
-                               uint64_t SectionAddress,
                                uint64_t FragmentOffset) const;
 
   /// LayoutOnce - Perform one layout iteration and return true if any offsets
@@ -765,8 +749,7 @@ public:
   // option is to make this abstract, and have targets provide concrete
   // implementations as we do with AsmParser.
   MCAssembler(MCContext &_Context, TargetAsmBackend &_Backend,
-              MCCodeEmitter &_Emitter, bool _PadSectionToAlignment,
-              raw_ostream &OS);
+              MCCodeEmitter &_Emitter, raw_ostream &OS);
   ~MCAssembler();
 
   MCContext &getContext() const { return Context; }
diff --git a/include/llvm/MC/MCExpr.h b/include/llvm/MC/MCExpr.h
index 888934e822..da3cebe414 100644
--- a/include/llvm/MC/MCExpr.h
+++ b/include/llvm/MC/MCExpr.h
@@ -10,6 +10,7 @@
 #ifndef LLVM_MC_MCEXPR_H
 #define LLVM_MC_MCEXPR_H
 
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/DataTypes.h"
 
@@ -18,10 +19,12 @@ class MCAsmInfo;
 class MCAsmLayout;
 class MCAssembler;
 class MCContext;
+class MCSectionData;
 class MCSymbol;
 class MCValue;
 class raw_ostream;
 class StringRef;
+typedef DenseMap<const MCSectionData*, uint64_t> SectionAddrMap;
 
 /// MCExpr - Base class for the full range of assembler expressions which are
 /// needed for parsing.
@@ -42,12 +45,14 @@ private:
   void operator=(const MCExpr&); // DO NOT IMPLEMENT
 
   bool EvaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm,
-                          const MCAsmLayout *Layout) const;
+                          const MCAsmLayout *Layout,
+                          const SectionAddrMap *Addrs) const;
 protected:
   explicit MCExpr(ExprKind _Kind) : Kind(_Kind) {}
 
   bool EvaluateAsRelocatableImpl(MCValue &Res, const MCAssembler *Asm,
                                  const MCAsmLayout *Layout,
+                                 const SectionAddrMap *Addrs,
                                  bool InSet) const;
 public:
   /// @name Accessors
@@ -76,6 +81,8 @@ public:
   bool EvaluateAsAbsolute(int64_t &Res) const;
   bool EvaluateAsAbsolute(int64_t &Res, const MCAssembler &Asm) const;
   bool EvaluateAsAbsolute(int64_t &Res, const MCAsmLayout &Layout) const;
+  bool EvaluateAsAbsolute(int64_t &Res, const MCAsmLayout &Layout,
+                          const SectionAddrMap &Addrs) const;
 
   /// EvaluateAsRelocatable - Try to evaluate the expression to a relocatable
   /// value, i.e. an expression of the fixed form (a - b + constant).
diff --git a/include/llvm/MC/MCObjectStreamer.h b/include/llvm/MC/MCObjectStreamer.h
index d130ba4bcd..c6dd96068f 100644
--- a/include/llvm/MC/MCObjectStreamer.h
+++ b/include/llvm/MC/MCObjectStreamer.h
@@ -37,8 +37,7 @@ class MCObjectStreamer : public MCStreamer {
 
 protected:
   MCObjectStreamer(MCContext &Context, TargetAsmBackend &TAB,
-                   raw_ostream &_OS, MCCodeEmitter *_Emitter,
-                   bool _PadSectionToAlignment);
+                   raw_ostream &_OS, MCCodeEmitter *_Emitter);
   ~MCObjectStreamer();
 
   MCSectionData *getCurrentSectionData() const {
diff --git a/include/llvm/MC/MCObjectWriter.h b/include/llvm/MC/MCObjectWriter.h
index 90fe6e8ee1..b819a5778f 100644
--- a/include/llvm/MC/MCObjectWriter.h
+++ b/include/llvm/MC/MCObjectWriter.h
@@ -62,7 +62,8 @@ public:
   ///
   /// This routine is called by the assembler after layout and relaxation is
   /// complete.
-  virtual void ExecutePostLayoutBinding(MCAssembler &Asm) = 0;
+  virtual void ExecutePostLayoutBinding(MCAssembler &Asm,
+                                        const MCAsmLayout &Layout) = 0;
 
   /// Record a relocation entry.
   ///