Proof of concept patch for merging the .s and ELF emission of the ARM arch attributes

lib/Target/ARM/ARMAsmPrinter.cpp

Index: lib/Target/ARM/ARMAsmPrinter.cpp
===================================================================
--- lib/Target/ARM/ARMAsmPrinter.cpp	(revision 115580)
+++ lib/Target/ARM/ARMAsmPrinter.cpp	(working copy)
@@ -107,6 +107,12 @@
     void EmitStartOfAsmFile(Module &M);
     void EmitEndOfAsmFile(Module &M);
 
+  private:
+    // Two helpers for EmitStartOfAsmFile() and EmitEndOfAsmFile()
+    void emitAsmAttributes(Module &M);
+    void emitELFAttributes(Module &M);
+  public:
+
     void PrintDebugValueComment(const MachineInstr *MI, raw_ostream &OS);
 
     MachineLocation getDebugValueLocation(const MachineInstr *MI) const {
@@ -422,45 +428,8 @@
 
   // Emit ARM Build Attributes
   if (Subtarget->isTargetELF()) {
-    // CPU Type
-    std::string CPUString = Subtarget->getCPUString();
-    if (CPUString != "generic")
-      OutStreamer.EmitRawText("\t.cpu " + Twine(CPUString));
 
-    // FIXME: Emit FPU type
-    if (Subtarget->hasVFP2())
-      OutStreamer.EmitRawText("\t.eabi_attribute " +
-                              Twine(ARMBuildAttrs::VFP_arch) + ", 2");
-
-    // Signal various FP modes.
-    if (!UnsafeFPMath) {
-      OutStreamer.EmitRawText("\t.eabi_attribute " +
-                              Twine(ARMBuildAttrs::ABI_FP_denormal) + ", 1");
-      OutStreamer.EmitRawText("\t.eabi_attribute " +
-                              Twine(ARMBuildAttrs::ABI_FP_exceptions) + ", 1");
-    }
-
-    if (NoInfsFPMath && NoNaNsFPMath)
-      OutStreamer.EmitRawText("\t.eabi_attribute " +
-                              Twine(ARMBuildAttrs::ABI_FP_number_model)+ ", 1");
-    else
-      OutStreamer.EmitRawText("\t.eabi_attribute " +
-                              Twine(ARMBuildAttrs::ABI_FP_number_model)+ ", 3");
-
-    // 8-bytes alignment stuff.
-    OutStreamer.EmitRawText("\t.eabi_attribute " +
-                            Twine(ARMBuildAttrs::ABI_align8_needed) + ", 1");
-    OutStreamer.EmitRawText("\t.eabi_attribute " +
-                            Twine(ARMBuildAttrs::ABI_align8_preserved) + ", 1");
-
-    // Hard float.  Use both S and D registers and conform to AAPCS-VFP.
-    if (Subtarget->isAAPCS_ABI() && FloatABIType == FloatABI::Hard) {
-      OutStreamer.EmitRawText("\t.eabi_attribute " +
-                              Twine(ARMBuildAttrs::ABI_HardFP_use) + ", 3");
-      OutStreamer.EmitRawText("\t.eabi_attribute " +
-                              Twine(ARMBuildAttrs::ABI_VFP_args) + ", 1");
-    }
-    // FIXME: Should we signal R9 usage?
+    emitAsmAttributes(M);
   }
 }
 
@@ -533,8 +502,67 @@
   }
 }
 
+
 //===----------------------------------------------------------------------===//
+// Helper routines for EmitStartOfAsmFile() and EmitEndOfAsmFile()
+// FIXME:
+// The following seem like one-off assembler flags, but they actually need
+// to appear in the .ARM.attributes section in ELF. This is the reason why
+// having a common interface to emit these for both the MC/.s and
+// MC/ELF/obj emission is complicated.
+// Instead of subclassing the MCELFStreamer, we do the work here.
 
+void ARMAsmPrinter::emitAsmAttributes(Module &M) {
+  if (!OutStreamer.hasRawTextSupport()) 
+    return;
+
+  // CPU Type
+  std::string CPUString = Subtarget->getCPUString();
+  if (CPUString != "generic")
+    OutStreamer.EmitRawText("\t.cpu " + Twine(CPUString));
+
+  // FIXME: Emit FPU type
+  if (Subtarget->hasVFP2())
+    OutStreamer.EmitRawText("\t.eabi_attribute " +
+                            Twine(ARMBuildAttrs::VFP_arch) + ", 2");
+
+  // Signal various FP modes.
+  if (!UnsafeFPMath) {
+    OutStreamer.EmitRawText("\t.eabi_attribute " +
+                            Twine(ARMBuildAttrs::ABI_FP_denormal) + ", 1");
+    OutStreamer.EmitRawText("\t.eabi_attribute " +
+                            Twine(ARMBuildAttrs::ABI_FP_exceptions) + ", 1");
+  }
+
+  if (NoInfsFPMath && NoNaNsFPMath)
+    OutStreamer.EmitRawText("\t.eabi_attribute " +
+                            Twine(ARMBuildAttrs::ABI_FP_number_model)+ ", 1");
+  else
+    OutStreamer.EmitRawText("\t.eabi_attribute " +
+                            Twine(ARMBuildAttrs::ABI_FP_number_model)+ ", 3");
+
+  // 8-bytes alignment stuff.
+  OutStreamer.EmitRawText("\t.eabi_attribute " +
+                          Twine(ARMBuildAttrs::ABI_align8_needed) + ", 1");
+  OutStreamer.EmitRawText("\t.eabi_attribute " +
+                          Twine(ARMBuildAttrs::ABI_align8_preserved) + ", 1");
+
+  // Hard float.  Use both S and D registers and conform to AAPCS-VFP.
+  if (Subtarget->isAAPCS_ABI() && FloatABIType == FloatABI::Hard) {
+    OutStreamer.EmitRawText("\t.eabi_attribute " +
+                            Twine(ARMBuildAttrs::ABI_HardFP_use) + ", 3");
+    OutStreamer.EmitRawText("\t.eabi_attribute " +
+                            Twine(ARMBuildAttrs::ABI_VFP_args) + ", 1");
+  }
+  // FIXME: Should we signal R9 usage?
+}
+
+void ARMAsmPrinter::emitELFAttributes(Module &M) {
+  // FIXME:
+}
+
+//===----------------------------------------------------------------------===//
+
 static MCSymbol *getPICLabel(const char *Prefix, unsigned FunctionNumber,
                              unsigned LabelId, MCContext &Ctx) {