[PPC] Add support for tune-cpu attribute

clang (like gcc) has the -mtune= command line option. This option
adds the "tune-cpu" attribute to a function. The intended functionality
is that the scheduling model of that cpu is used. E.g. -mtune=pwr9 -march=pwr8
generates only instructions supported on pwr8 but uses the scheduling model
of pwr9 for it.
This PR adds the infrastructure to support this in LLVM.
clang support was added in https://reviews.llvm.org/D130526.

Reviewed By: amyk, qiucf

Differential Revision: https://reviews.llvm.org/D138317

diff --git a/llvm/lib/Target/PowerPC/PPCSubtarget.cpp b/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
index fb37bf4..e32a2ed 100644 (file)
--- a/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
+++ b/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
@@ -48,18 +48,20 @@ static cl::opt<bool>
                            cl::init(false), cl::Hidden);
 
 PPCSubtarget &PPCSubtarget::initializeSubtargetDependencies(StringRef CPU,
+                                                            StringRef TuneCPU,
                                                             StringRef FS) {
   initializeEnvironment();
-  initSubtargetFeatures(CPU, FS);
+  initSubtargetFeatures(CPU, TuneCPU, FS);
   return *this;
 }
 
 PPCSubtarget::PPCSubtarget(const Triple &TT, const std::string &CPU,
-                           const std::string &FS, const PPCTargetMachine &TM)
-    : PPCGenSubtargetInfo(TT, CPU, /*TuneCPU*/ CPU, FS), TargetTriple(TT),
+                           const std::string &TuneCPU, const std::string &FS,
+                           const PPCTargetMachine &TM)
+    : PPCGenSubtargetInfo(TT, CPU, TuneCPU, FS), TargetTriple(TT),
       IsPPC64(TargetTriple.getArch() == Triple::ppc64 ||
               TargetTriple.getArch() == Triple::ppc64le),
-      TM(TM), FrameLowering(initializeSubtargetDependencies(CPU, FS)),
+      TM(TM), FrameLowering(initializeSubtargetDependencies(CPU, TuneCPU, FS)),
       InstrInfo(*this), TLInfo(TM, *this) {
   CallLoweringInfo.reset(new PPCCallLowering(*getTargetLowering()));
   Legalizer.reset(new PPCLegalizerInfo(*this));
@@ -76,7 +78,8 @@ void PPCSubtarget::initializeEnvironment() {
   HasPOPCNTD = POPCNTD_Unavailable;
 }
 
-void PPCSubtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {
+void PPCSubtarget::initSubtargetFeatures(StringRef CPU, StringRef TuneCPU,
+                                         StringRef FS) {
   // Determine default and user specified characteristics
   std::string CPUName = std::string(CPU);
   if (CPUName.empty() || CPU == "generic") {
@@ -89,11 +92,14 @@ void PPCSubtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {
       CPUName = "generic";
   }
 
+  // Determine the CPU to schedule for.
+  if (TuneCPU.empty()) TuneCPU = CPUName;
+
   // Initialize scheduling itinerary for the specified CPU.
   InstrItins = getInstrItineraryForCPU(CPUName);
 
   // Parse features string.
-  ParseSubtargetFeatures(CPUName, /*TuneCPU*/ CPUName, FS);
+  ParseSubtargetFeatures(CPUName, TuneCPU, FS);
 
   // If the user requested use of 64-bit regs, but the cpu selected doesn't
   // support it, ignore.

diff --git a/llvm/lib/Target/PowerPC/PPCSubtarget.h b/llvm/lib/Target/PowerPC/PPCSubtarget.h
index 007ffd5..05ab0d4 100644 (file)
--- a/llvm/lib/Target/PowerPC/PPCSubtarget.h
+++ b/llvm/lib/Target/PowerPC/PPCSubtarget.h
@@ -116,7 +116,8 @@ public:
   /// This constructor initializes the data members to match that
   /// of the specified triple.
   ///
-  PPCSubtarget(const Triple &TT, const std::string &CPU, const std::string &FS,
+  PPCSubtarget(const Triple &TT, const std::string &CPU,
+               const std::string &TuneCPU, const std::string &FS,
                const PPCTargetMachine &TM);
 
   /// ParseSubtargetFeatures - Parses features string setting specified
@@ -153,13 +154,16 @@ public:
   }
   const PPCTargetMachine &getTargetMachine() const { return TM; }
 
-  /// initializeSubtargetDependencies - Initializes using a CPU and feature string
-  /// so that we can use initializer lists for subtarget initialization.
-  PPCSubtarget &initializeSubtargetDependencies(StringRef CPU, StringRef FS);
+  /// initializeSubtargetDependencies - Initializes using a CPU, a TuneCPU,  and
+  /// feature string so that we can use initializer lists for subtarget
+  /// initialization.
+  PPCSubtarget &initializeSubtargetDependencies(StringRef CPU,
+                                                StringRef TuneCPU,
+                                                StringRef FS);
 
 private:
   void initializeEnvironment();
-  void initSubtargetFeatures(StringRef CPU, StringRef FS);
+  void initSubtargetFeatures(StringRef CPU, StringRef TuneCPU, StringRef FS);
 
 public:
   /// isPPC64 - Return true if we are generating code for 64-bit pointer mode.

diff --git a/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp b/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp
index 0a020b9..9aea5af 100644 (file)
--- a/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp
+++ b/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp
@@ -341,10 +341,13 @@ PPCTargetMachine::~PPCTargetMachine() = default;
 const PPCSubtarget *
 PPCTargetMachine::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;
 
@@ -359,14 +362,14 @@ PPCTargetMachine::getSubtargetImpl(const Function &F) const {
   if (SoftFloat)
     FS += FS.empty() ? "-hard-float" : ",-hard-float";
 
-  auto &I = SubtargetMap[CPU + FS];
+  auto &I = SubtargetMap[CPU + TuneCPU + FS];
   if (!I) {
     // This needs to be done before we create a new subtarget since any
     // creation will depend on the TM and the code generation flags on the
     // function that reside in TargetOptions.
     resetTargetOptions(F);
     I = std::make_unique<PPCSubtarget>(
-        TargetTriple, CPU,
+        TargetTriple, CPU, TuneCPU,
         // FIXME: It would be good to have the subtarget additions here
         // not necessary. Anything that turns them on/off (overrides) ends
         // up being put at the end of the feature string, but the defaults