MC/Mach-O: On second thought, use a custom hook for enabling aggressive

IsSymbolRefDifferenceFullyResolved, it turns out this does change behavior on
enough cases for x86-32 that I would rather wait a bit on it.
 - In practice, we will want to change this eventually because it only means we
   generate less relocations (it also eliminates the need for the horrible
   '.set' hack that Darwin requires in some places).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122042 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 15 insertions, 4 deletions

diff --git a/include/llvm/MC/MCMachObjectWriter.h b/include/llvm/MC/MCMachObjectWriter.h
index 8c67d257a3..6dfa3225d8 100644
--- a/include/llvm/MC/MCMachObjectWriter.h
+++ b/include/llvm/MC/MCMachObjectWriter.h
@@ -19,10 +19,14 @@ class MCMachObjectTargetWriter {
   const unsigned Is64Bit : 1;
   const uint32_t CPUType;
   const uint32_t CPUSubtype;
+  // FIXME: Remove this, we should just always use it once we no longer care
+  // about Darwin 'as' compatibility.
+  const unsigned UseAggressiveSymbolFolding : 1;
 
 protected:
   MCMachObjectTargetWriter(bool Is64Bit_, uint32_t CPUType_,
-                           uint32_t CPUSubtype_);
+                           uint32_t CPUSubtype_,
+                           bool UseAggressiveSymbolFolding_ = false);
 
 public:
   virtual ~MCMachObjectTargetWriter();
@@ -31,6 +35,7 @@ public:
   /// @{
 
   bool is64Bit() const { return Is64Bit; }
+  bool useAggressiveSymbolFolding() const { return UseAggressiveSymbolFolding; }
   uint32_t getCPUType() const { return CPUType; }
   uint32_t getCPUSubtype() const { return CPUSubtype; }
 
diff --git a/lib/MC/MCMachObjectTargetWriter.cpp b/lib/MC/MCMachObjectTargetWriter.cpp
index 4dfc0a815f..146cebf01a 100644
--- a/lib/MC/MCMachObjectTargetWriter.cpp
+++ b/lib/MC/MCMachObjectTargetWriter.cpp
@@ -12,8 +12,10 @@
 using namespace llvm;
 
 MCMachObjectTargetWriter::MCMachObjectTargetWriter(
-  bool Is64Bit_, uint32_t CPUType_, uint32_t CPUSubtype_)
-  : Is64Bit(Is64Bit_), CPUType(CPUType_), CPUSubtype(CPUSubtype_) {
+  bool Is64Bit_, uint32_t CPUType_, uint32_t CPUSubtype_,
+  bool UseAggressiveSymbolFolding_)
+  : Is64Bit(Is64Bit_), CPUType(CPUType_), CPUSubtype(CPUSubtype_),
+    UseAggressiveSymbolFolding(UseAggressiveSymbolFolding_) {
 }
 
 MCMachObjectTargetWriter::~MCMachObjectTargetWriter() {
diff --git a/lib/MC/MachObjectWriter.cpp b/lib/MC/MachObjectWriter.cpp
index 17615eef69..6ebc782c8e 100644
--- a/lib/MC/MachObjectWriter.cpp
+++ b/lib/MC/MachObjectWriter.cpp
@@ -1126,6 +1126,9 @@ public:
   bool IsSymbolRefDifferenceFullyResolved(const MCAssembler &Asm,
                                           const MCSymbolRefExpr *A,
                                           const MCSymbolRefExpr *B) const {
+    if (!TargetObjectWriter->useAggressiveSymbolFolding())
+      return false;
+
     // The effective address is
     //     addr(atom(A)) + offset(A)
     //   - addr(atom(B)) - offset(B)
diff --git a/lib/Target/X86/X86AsmBackend.cpp b/lib/Target/X86/X86AsmBackend.cpp
index 3f58e43ea1..fe894ab7a1 100644
--- a/lib/Target/X86/X86AsmBackend.cpp
+++ b/lib/Target/X86/X86AsmBackend.cpp
@@ -50,7 +50,8 @@ class X86MachObjectWriter : public MCMachObjectTargetWriter {
 public:
   X86MachObjectWriter(bool Is64Bit, uint32_t CPUType,
                       uint32_t CPUSubtype)
-    : MCMachObjectTargetWriter(Is64Bit, CPUType, CPUSubtype) {}
+    : MCMachObjectTargetWriter(Is64Bit, CPUType, CPUSubtype,
+                               /*UseAggressiveSymbolFolding=*/Is64Bit) {}
 };
 
 class X86AsmBackend : public TargetAsmBackend {