[ARM] Generate ABI_optimization_goals build attribute, as described in the ARM ARM.

Summary:
Since this build attribute corresponds to a whole module, and
different functions in a module may differ in the optimizations
enabled for them, this attribute is emitted after all functions,
and only in the case that the optimization goals for all
functions match.

Reviewers: logan, hans

Subscribers: aemerson, rengolin, llvm-commits

Differential Revision: http://reviews.llvm.org/D14934

llvm-svn: 254201

2 files changed, 46 insertions, 4 deletions

diff --git a/llvm/lib/Target/ARM/ARMAsmPrinter.cpp b/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
index 67ebfa2b581..2a41c5cb60f 100644
--- a/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
+++ b/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
@@ -60,7 +60,7 @@ using namespace llvm;
 ARMAsmPrinter::ARMAsmPrinter(TargetMachine &TM,
                              std::unique_ptr<MCStreamer> Streamer)
     : AsmPrinter(TM, std::move(Streamer)), AFI(nullptr), MCP(nullptr),
-      InConstantPool(false) {}
+      InConstantPool(false), OptimizationGoals(-1) {}
 
 void ARMAsmPrinter::EmitFunctionBodyEnd() {
   // Make sure to terminate any constant pools that were at the end
@@ -106,9 +106,38 @@ bool ARMAsmPrinter::runOnMachineFunction(MachineFunction &MF) {
   Subtarget = &MF.getSubtarget<ARMSubtarget>();
 
   SetupMachineFunction(MF);
+  const Function* F = MF.getFunction();
+  const TargetMachine& TM = MF.getTarget();
+
+  // Calculate this function's optimization goal.
+  unsigned OptimizationGoal;
+  if (F->hasFnAttribute(Attribute::OptimizeNone))
+    // For best debugging illusion, speed and small size sacrificed
+    OptimizationGoal = 6;
+  else if (F->optForMinSize())
+    // Aggressively for small size, speed and debug illusion sacrificed
+    OptimizationGoal = 4;
+  else if (F->optForSize())
+    // For small size, but speed and debugging illusion preserved
+    OptimizationGoal = 3;
+  else if (TM.getOptLevel() == CodeGenOpt::Aggressive)
+    // Aggressively for speed, small size and debug illusion sacrificed
+    OptimizationGoal = 2;
+  else if (TM.getOptLevel() > CodeGenOpt::None)
+    // For speed, but small size and good debug illusion preserved
+    OptimizationGoal = 1;
+  else // TM.getOptLevel() == CodeGenOpt::None
+    // For good debugging, but speed and small size preserved
+    OptimizationGoal = 5;
+
+  // Combine a new optimization goal with existing ones.
+  if (OptimizationGoals == -1) // uninitialized goals
+    OptimizationGoals = OptimizationGoal;
+  else if (OptimizationGoals != OptimizationGoal) // conflicting goals
+    OptimizationGoals = 0;
 
   if (Subtarget->isTargetCOFF()) {
-    bool Internal = MF.getFunction()->hasInternalLinkage();
+    bool Internal = F->hasInternalLinkage();
     COFF::SymbolStorageClass Scl = Internal ? COFF::IMAGE_SYM_CLASS_STATIC
                                             : COFF::IMAGE_SYM_CLASS_EXTERNAL;
     int Type = COFF::IMAGE_SYM_DTYPE_FUNCTION << COFF::SCT_COMPLEX_TYPE_SHIFT;
@@ -506,6 +535,16 @@ void ARMAsmPrinter::EmitEndOfAsmFile(Module &M) {
     // generates code that does this, it is always safe to set.
     OutStreamer->EmitAssemblerFlag(MCAF_SubsectionsViaSymbols);
   }
+
+  // The last attribute to be emitted is ABI_optimization_goals
+  MCTargetStreamer &TS = *OutStreamer->getTargetStreamer();
+  ARMTargetStreamer &ATS = static_cast<ARMTargetStreamer &>(TS);
+
+  if (OptimizationGoals > 0)
+    ATS.emitAttribute(ARMBuildAttrs::ABI_optimization_goals, OptimizationGoals);
+  OptimizationGoals = -1;
+
+  ATS.finishAttributeSection();
 }
 
 //===----------------------------------------------------------------------===//
@@ -798,8 +837,6 @@ void ARMAsmPrinter::emitAttributes() {
   else if (STI.hasVirtualization())
     ATS.emitAttribute(ARMBuildAttrs::Virtualization_use,
                       ARMBuildAttrs::AllowVirtualization);
-
-  ATS.finishAttributeSection();
 }
 
 //===----------------------------------------------------------------------===//
diff --git a/llvm/lib/Target/ARM/ARMAsmPrinter.h b/llvm/lib/Target/ARM/ARMAsmPrinter.h
index fb925f162f7..ed7be2de51c 100644
--- a/llvm/lib/Target/ARM/ARMAsmPrinter.h
+++ b/llvm/lib/Target/ARM/ARMAsmPrinter.h
@@ -51,6 +51,11 @@ class LLVM_LIBRARY_VISIBILITY ARMAsmPrinter : public AsmPrinter {
   /// labels used for ARMv4t thumb code to make register indirect calls.
   SmallVector<std::pair<unsigned, MCSymbol*>, 4> ThumbIndirectPads;
 
+  /// OptimizationGoals - Maintain a combined optimization goal for all
+  /// functions in a module: one of Tag_ABI_optimization_goals values,
+  /// -1 if uninitialized, 0 if conflicting goals
+  int OptimizationGoals;
+
 public:
   explicit ARMAsmPrinter(TargetMachine &TM,
                          std::unique_ptr<MCStreamer> Streamer);