MachO: direct-to-object attribute for data-in-code markers.

The target backend can support data-in-code load commands even when
the assembler doesn't, or vice-versa. Allow targets to opt-in for
direct-to-object.

PR13973.

llvm-svn: 164974

llvm/include/llvm/MC/MCAsmBackend.h

@@ -36,6 +36,7 @@ protected: // Can only create subclasses.
   MCAsmBackend();
 
   unsigned HasReliableSymbolDifference : 1;
+  unsigned HasDataInCodeSupport : 1;
 
 public:
   virtual ~MCAsmBackend();
@@ -65,6 +66,12 @@ public:
     return HasReliableSymbolDifference;
   }
 
+  /// hasDataInCodeSupport - Check whether this target implements data-in-code
+  /// markers. If not, data region directives will be ignored.
+  bool hasDataInCodeSupport() const {
+    return HasDataInCodeSupport;
+  }
+
   /// doesSectionRequireSymbols - Check whether the given section requires that
   /// all symbols (even temporaries) have symbol table entries.
   virtual bool doesSectionRequireSymbols(const MCSection &Section) const {

llvm/lib/MC/MCAsmBackend.cpp

@@ -12,12 +12,9 @@
 using namespace llvm;
 
 MCAsmBackend::MCAsmBackend()
-  : HasReliableSymbolDifference(false)
-{
-}
+  : HasReliableSymbolDifference(false), HasDataInCodeSupport(false) {}
 
-MCAsmBackend::~MCAsmBackend() {
-}
+MCAsmBackend::~MCAsmBackend() {}
 
 const MCFixupKindInfo &
 MCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {

llvm/lib/MC/MCMachOStreamer.cpp

@@ -139,6 +139,8 @@ void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
 }
 
 void MCMachOStreamer::EmitDataRegion(DataRegionData::KindTy Kind) {
+  if (!getAssembler().getBackend().hasDataInCodeSupport())
+    return;
   // Create a temporary label to mark the start of the data region.
   MCSymbol *Start = getContext().CreateTempSymbol();
   EmitLabel(Start);
@@ -149,6 +151,8 @@ void MCMachOStreamer::EmitDataRegion(DataRegionData::KindTy Kind) {
 }
 
 void MCMachOStreamer::EmitDataRegionEnd() {
+  if (!getAssembler().getBackend().hasDataInCodeSupport())
+    return;
   std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
   assert(Regions.size() && "Mismatched .end_data_region!");
   DataRegionData &Data = Regions.back();

llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp

@@ -593,7 +593,9 @@ public:
   const object::mach::CPUSubtypeARM Subtype;
   DarwinARMAsmBackend(const Target &T, const StringRef TT,
                       object::mach::CPUSubtypeARM st)
-    : ARMAsmBackend(T, TT), Subtype(st) { }
+    : ARMAsmBackend(T, TT), Subtype(st) {
+      HasDataInCodeSupport = true;
+    }
 
   MCObjectWriter *createObjectWriter(raw_ostream &OS) const {
     return createARMMachObjectWriter(OS, /*Is64Bit=*/false,

llvm/test/MC/MachO/lit.local.cfg

@@ -1,4 +1,4 @@
-config.suffixes = ['.s']
+config.suffixes = ['.s', '.ll']
 
 targets = set(config.root.targets_to_build.split())
 if not 'X86' in targets:

llvm/test/MC/MachO/x86-data-in-code.ll

@@ -0,0 +1,108 @@
+; RUN: llc -O0 -mtriple=x86_64-apple-darwin -filetype=obj -o - %s | macho-dump | FileCheck %s
+
+; There should not be a data-in-code load command (type 0x29) for x86_64
+; jump tables, even though they are in the text section.
+; CHECK: 'num_load_commands'
+; CHECK-NOT: (('command', 41)
+
+define void @foo(i32* %ptr) nounwind ssp {
+  %tmp = load i32* %ptr, align 4
+  switch i32 %tmp, label %default [
+    i32 11, label %bb0
+    i32 10, label %bb1
+    i32 8, label %bb2
+    i32 4, label %bb3
+    i32 2, label %bb4
+    i32 6, label %bb5
+    i32 9, label %bb6
+    i32 15, label %bb7
+    i32 1, label %bb8
+    i32 3, label %bb9
+    i32 5, label %bb10
+    i32 30, label %bb11
+    i32 31, label %bb12
+    i32 13, label %bb13
+    i32 14, label %bb14
+    i32 20, label %bb15
+    i32 19, label %bb16
+    i32 17, label %bb17
+    i32 18, label %bb18
+    i32 21, label %bb19
+    i32 22, label %bb20
+    i32 16, label %bb21
+    i32 24, label %bb22
+    i32 25, label %bb23
+    i32 26, label %bb24
+    i32 27, label %bb25
+    i32 28, label %bb26
+    i32 23, label %bb27
+    i32 12, label %bb28
+  ]
+
+default:
+  br label %exit
+bb0:
+  br label %exit
+bb1:
+  br label %exit
+bb2:
+  br label %exit
+bb3:
+  br label %exit
+bb4:
+  br label %exit
+bb5:
+  br label %exit
+bb6:
+  br label %exit
+bb7:
+  br label %exit
+bb8:
+  br label %exit
+bb9:
+  br label %exit
+bb10:
+  br label %exit
+bb11:
+  br label %exit
+bb12:
+  br label %exit
+bb13:
+  br label %exit
+bb14:
+  br label %exit
+bb15:
+  br label %exit
+bb16:
+  br label %exit
+bb17:
+  br label %exit
+bb18:
+  br label %exit
+bb19:
+  br label %exit
+bb20:
+  br label %exit
+bb21:
+  br label %exit
+bb22:
+  br label %exit
+bb23:
+  br label %exit
+bb24:
+  br label %exit
+bb25:
+  br label %exit
+bb26:
+  br label %exit
+bb27:
+  br label %exit
+bb28:
+  br label %exit
+
+
+exit:
+
+  ret void
+}
+