Sparc: Add 64-bit feature (#157445)

Add a 64-bit feature so a subtarget feature check can tell the
pointer size, for future use with HwMode.

This is kind of a hack, but this is closer to what other targets do.
To use HwModes, there needs to be a subtarget feature. Every other
target kludges the module level properties into a subtarget feature
for use here, which requires pre/post processing the subtarget features.
The APIs for this aren't great. I tried doing something different,
closer to what hexagon does, rather than what x86 does to see if it
was any nicer. It almost is, except for some reason we don't have an
API to directly set a bit in the FeatureBitset.

Also the test coverage for the different ABI options isn't great.
e.g. v9 as a feature almost works, except a single test breaks
that uses a sparc32 triple with an explicit v9 feature.

Author: arsenm

llvm/lib/Target/Sparc/MCTargetDesc/SparcMCTargetDesc.cpp

@@ -81,8 +81,16 @@ static MCRegisterInfo *createSparcMCRegisterInfo(const Triple &TT) {
 static MCSubtargetInfo *
 createSparcMCSubtargetInfo(const Triple &TT, StringRef CPU, StringRef FS) {
   if (CPU.empty())
-    CPU = (TT.getArch() == Triple::sparcv9) ? "v9" : "v8";
-  return createSparcMCSubtargetInfoImpl(TT, CPU, /*TuneCPU*/ CPU, FS);
+    CPU = TT.getArch() == Triple::sparcv9 ? "v9" : "v8";
+
+  MCSubtargetInfo *STI =
+      createSparcMCSubtargetInfoImpl(TT, CPU, /*TuneCPU=*/CPU, FS);
+  if (TT.isSPARC64() && !STI->hasFeature(Sparc::Feature64Bit)) {
+    FeatureBitset Features = STI->getFeatureBits();
+    STI->setFeatureBits(Features.set(Sparc::Feature64Bit));
+  }
+
+  return STI;
 }
 
 static MCTargetStreamer *

llvm/lib/Target/Sparc/MCTargetDesc/SparcMCTargetDesc.h

@@ -28,6 +28,7 @@ class MCRegisterInfo;
 class MCSubtargetInfo;
 class MCTargetOptions;
 class Target;
+class Triple;
 
 MCCodeEmitter *createSparcMCCodeEmitter(const MCInstrInfo &MCII,
                                         MCContext &Ctx);

llvm/lib/Target/Sparc/Sparc.td

@@ -34,6 +34,9 @@ def FeatureNoFMULS
 def FeatureV9
   : SubtargetFeature<"v9", "IsV9", "true",
                      "Enable SPARC-V9 instructions">;
+def Feature64Bit : SubtargetFeature<"64bit", "Is64Bit", "true",
+                                    "Enable 64-bit mode", [FeatureV9]>;
+
 def FeatureV8Plus
   : SubtargetFeature<"v8plus", "IsV8Plus", "true",
                      "Enable V8+ mode, allowing use of 64-bit V9 instructions in 32-bit code">;

llvm/lib/Target/Sparc/SparcSubtarget.cpp

@@ -28,17 +28,24 @@ void SparcSubtarget::anchor() { }
 
 SparcSubtarget &SparcSubtarget::initializeSubtargetDependencies(
     StringRef CPU, StringRef TuneCPU, StringRef FS) {
+  const Triple &TT = getTargetTriple();
   // Determine default and user specified characteristics
   std::string CPUName = std::string(CPU);
   if (CPUName.empty())
-    CPUName = getTargetTriple().isSPARC64() ? "v9" : "v8";
+    CPUName = TT.isSPARC64() ? "v9" : "v8";
 
   if (TuneCPU.empty())
     TuneCPU = CPUName;
 
   // Parse features string.
   ParseSubtargetFeatures(CPUName, TuneCPU, FS);
 
+  if (!Is64Bit && TT.isSPARC64()) {
+    FeatureBitset Features = getFeatureBits();
+    setFeatureBits(Features.set(Sparc::Feature64Bit));
+    Is64Bit = true;
+  }
+
   // Popc is a v9-only instruction.
   if (!IsV9)
     UsePopc = false;
@@ -50,7 +57,6 @@ SparcSubtarget::SparcSubtarget(const StringRef &CPU, const StringRef &TuneCPU,
                                const StringRef &FS, const TargetMachine &TM)
     : SparcGenSubtargetInfo(TM.getTargetTriple(), CPU, TuneCPU, FS),
       ReserveRegister(TM.getMCRegisterInfo()->getNumRegs()),
-      Is64Bit(TM.getTargetTriple().isSPARC64()),
       InstrInfo(initializeSubtargetDependencies(CPU, TuneCPU, FS)),
       TLInfo(TM, *this), FrameLowering(*this) {
   TSInfo = std::make_unique<SparcSelectionDAGInfo>();

llvm/lib/Target/Sparc/SparcSubtarget.h

@@ -36,8 +36,6 @@ class SparcSubtarget : public SparcGenSubtargetInfo {
 
   virtual void anchor();
 
-  const bool Is64Bit;
-
 #define GET_SUBTARGETINFO_MACRO(ATTRIBUTE, DEFAULT, GETTER)                    \
   bool ATTRIBUTE = DEFAULT;
 #include "SparcGenSubtargetInfo.inc"
@@ -79,8 +77,6 @@ class SparcSubtarget : public SparcGenSubtargetInfo {
                                                   StringRef TuneCPU,
                                                   StringRef FS);
 
-  bool is64Bit() const { return Is64Bit; }
-
   /// The 64-bit ABI uses biased stack and frame pointers, so the stack frame
   /// of the current function is the area from [%sp+BIAS] to [%fp+BIAS].
   int64_t getStackPointerBias() const {