[SPARC] Consume tune-cpu directive in the backend (#77195)

This lets the backend read the `tune-cpu` directive that is emitted by the frontend.

No changes are needed for clang as it is already emits it.

Author: koachan

clang/include/clang/Driver/Options.td

@@ -5172,7 +5172,7 @@ def module_file_info : Flag<["-"], "module-file-info">, Flags<[]>,
   HelpText<"Provide information about a particular module file">;
 def mthumb : Flag<["-"], "mthumb">, Group<m_Group>;
 def mtune_EQ : Joined<["-"], "mtune=">, Group<m_Group>,
-  HelpText<"Only supported on AArch64, PowerPC, RISC-V, SystemZ, and X86">;
+  HelpText<"Only supported on AArch64, PowerPC, RISC-V, SPARC, SystemZ, and X86">;
 def multi__module : Flag<["-"], "multi_module">;
 def multiply__defined__unused : Separate<["-"], "multiply_defined_unused">;
 def multiply__defined : Separate<["-"], "multiply_defined">;

llvm/lib/Target/Sparc/SparcSubtarget.cpp

@@ -12,6 +12,7 @@
 
 #include "SparcSubtarget.h"
 #include "Sparc.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/MC/TargetRegistry.h"
 #include "llvm/Support/MathExtras.h"
 
@@ -25,15 +26,18 @@ using namespace llvm;
 
 void SparcSubtarget::anchor() { }
 
-SparcSubtarget &SparcSubtarget::initializeSubtargetDependencies(StringRef CPU,
-                                                                StringRef FS) {
+SparcSubtarget &SparcSubtarget::initializeSubtargetDependencies(
+    StringRef CPU, StringRef TuneCPU, StringRef FS) {
   // Determine default and user specified characteristics
   std::string CPUName = std::string(CPU);
   if (CPUName.empty())
     CPUName = (Is64Bit) ? "v9" : "v8";
 
+  if (TuneCPU.empty())
+    TuneCPU = CPUName;
+
   // Parse features string.
-  ParseSubtargetFeatures(CPUName, /*TuneCPU*/ CPUName, FS);
+  ParseSubtargetFeatures(CPUName, TuneCPU, FS);
 
   // Popc is a v9-only instruction.
   if (!IsV9)
@@ -42,11 +46,12 @@ SparcSubtarget &SparcSubtarget::initializeSubtargetDependencies(StringRef CPU,
   return *this;
 }
 
-SparcSubtarget::SparcSubtarget(const Triple &TT, const std::string &CPU,
-                               const std::string &FS, const TargetMachine &TM,
+SparcSubtarget::SparcSubtarget(const StringRef &CPU, const StringRef &TuneCPU,
+                               const StringRef &FS, const TargetMachine &TM,
                                bool is64Bit)
-    : SparcGenSubtargetInfo(TT, CPU, /*TuneCPU*/ CPU, FS), TargetTriple(TT),
-      Is64Bit(is64Bit), InstrInfo(initializeSubtargetDependencies(CPU, FS)),
+    : SparcGenSubtargetInfo(TM.getTargetTriple(), CPU, TuneCPU, FS),
+      TargetTriple(TM.getTargetTriple()), Is64Bit(is64Bit),
+      InstrInfo(initializeSubtargetDependencies(CPU, TuneCPU, FS)),
       TLInfo(TM, *this), FrameLowering(*this) {}
 
 int SparcSubtarget::getAdjustedFrameSize(int frameSize) const {

llvm/lib/Target/Sparc/SparcSubtarget.h

@@ -44,8 +44,8 @@ class SparcSubtarget : public SparcGenSubtargetInfo {
   SparcFrameLowering FrameLowering;
 
 public:
-  SparcSubtarget(const Triple &TT, const std::string &CPU,
-                 const std::string &FS, const TargetMachine &TM, bool is64bit);
+  SparcSubtarget(const StringRef &CPU, const StringRef &TuneCPU,
+                 const StringRef &FS, const TargetMachine &TM, bool is64bit);
 
   const SparcInstrInfo *getInstrInfo() const override { return &InstrInfo; }
   const TargetFrameLowering *getFrameLowering() const override {
@@ -70,7 +70,9 @@ class SparcSubtarget : public SparcGenSubtargetInfo {
   /// ParseSubtargetFeatures - Parses features string setting specified
   /// subtarget options.  Definition of function is auto generated by tblgen.
   void ParseSubtargetFeatures(StringRef CPU, StringRef TuneCPU, StringRef FS);
-  SparcSubtarget &initializeSubtargetDependencies(StringRef CPU, StringRef FS);
+  SparcSubtarget &initializeSubtargetDependencies(StringRef CPU,
+                                                  StringRef TuneCPU,
+                                                  StringRef FS);
 
   bool is64Bit() const { return Is64Bit; }
 

llvm/lib/Target/Sparc/SparcTargetMachine.cpp

@@ -116,10 +116,13 @@ SparcTargetMachine::~SparcTargetMachine() = default;
 const SparcSubtarget *
 SparcTargetMachine::getSubtargetImpl(const Function &F) const {
   Attribute CPUAttr = F.getFnAttribute("target-cpu");
+  Attribute TuneAttr = F.getFnAttribute("tune-cpu");
   Attribute FSAttr = F.getFnAttribute("target-features");
 
   std::string CPU =
       CPUAttr.isValid() ? CPUAttr.getValueAsString().str() : TargetCPU;
+  std::string TuneCPU =
+      TuneAttr.isValid() ? TuneAttr.getValueAsString().str() : CPU;
   std::string FS =
       FSAttr.isValid() ? FSAttr.getValueAsString().str() : TargetFS;
 
@@ -137,8 +140,8 @@ SparcTargetMachine::getSubtargetImpl(const Function &F) const {
     // creation will depend on the TM and the code generation flags on the
     // function that reside in TargetOptions.
     resetTargetOptions(F);
-    I = std::make_unique<SparcSubtarget>(TargetTriple, CPU, FS, *this,
-                                          this->is64Bit);
+    I = std::make_unique<SparcSubtarget>(CPU, TuneCPU, FS, *this,
+                                         this->is64Bit);
   }
   return I.get();
 }