AMDGPU: Add subtarget feature for instruction rates

[• tstellarAMD]

LGTM.

[arsenm]

r258085

lib/Target/AMDGPU/AMDGPU.td

def FeatureFP64Denormals : SubtargetFeature<"fp64-denormals",
         [FeatureFP64]>;
 
 def FeatureFastFMAF32 : SubtargetFeature<"fast-fmaf",
         "FastFMAF32",
         "true",
         "Assuming f32 fma is at least as fast as mul + add",
         []>;
 
+def HalfRate64Ops : SubtargetFeature<"half-rate-64-ops",
+        "HalfRate64Ops",
+        "true",
+        "Most fp64 instructions are half rate instead of quarter",
+        []>;
+
 // Some instructions do not support denormals despite this flag. Using
 // fp32 denormals also causes instructions to run at the double
 // precision rate for the device.
 def FeatureFP32Denormals : SubtargetFeature<"fp32-denormals",
         "FP32Denormals",
         "true",
         "Enable single precision denormal handling">;
 

lib/Target/AMDGPU/AMDGPUSubtarget.h

private:
   bool R600ALUInst;
   bool HasVertexCache;
   short TexVTXClauseSize;
   Generation Gen;
   bool FP64;
   bool FP64Denormals;
   bool FP32Denormals;
   bool FastFMAF32;
+  bool HalfRate64Ops;
   bool CaymanISA;
   bool FlatAddressSpace;
   bool FlatForGlobal;
   bool EnableIRStructurizer;
   bool EnablePromoteAlloca;
   bool EnableIfCvt;
   bool EnableLoadStoreOpt;
   bool EnableUnsafeDSOffsetFolding;
public:
   bool hasFP64Denormals() const {
     return FP64Denormals;
   }
 
   bool hasFastFMAF32() const {
     return FastFMAF32;
   }
 
+  bool hasHalfRate64Ops() const {
+    return HalfRate64Ops;
+  }
+
   bool hasFlatAddressSpace() const {
     return FlatAddressSpace;
   }
 
   bool useFlatForGlobal() const {
     return FlatForGlobal;
   }
 

lib/Target/AMDGPU/AMDGPUSubtarget.cpp

 }
 
 AMDGPUSubtarget::AMDGPUSubtarget(const Triple &TT, StringRef GPU, StringRef FS,
                                  TargetMachine &TM)
     : AMDGPUGenSubtargetInfo(TT, GPU, FS), DevName(GPU), Is64bit(false),
       DumpCode(false), R600ALUInst(false), HasVertexCache(false),
       TexVTXClauseSize(0), Gen(AMDGPUSubtarget::R600), FP64(false),
       FP64Denormals(false), FP32Denormals(false), FastFMAF32(false),
-      CaymanISA(false), FlatAddressSpace(false), FlatForGlobal(false),
-      EnableIRStructurizer(true), EnablePromoteAlloca(false), EnableIfCvt(true),
-      EnableLoadStoreOpt(false), EnableUnsafeDSOffsetFolding(false),
+      HalfRate64Ops(false), CaymanISA(false), FlatAddressSpace(false),
+      FlatForGlobal(false), EnableIRStructurizer(true),
+      EnablePromoteAlloca(false),
+      EnableIfCvt(true), EnableLoadStoreOpt(false),
+      EnableUnsafeDSOffsetFolding(false),
       EnableXNACK(false),
-      WavefrontSize(0), CFALUBug(false), LocalMemorySize(0),
+      WavefrontSize(0), CFALUBug(false),
+      LocalMemorySize(0),
       EnableVGPRSpilling(false), SGPRInitBug(false), IsGCN(false),
       GCN1Encoding(false), GCN3Encoding(false), CIInsts(false), LDSBankCount(0),
       IsaVersion(ISAVersion0_0_0), EnableHugeScratchBuffer(false),
       FrameLowering(nullptr),
       InstrItins(getInstrItineraryForCPU(GPU)), TargetTriple(TT) {
 
   initializeSubtargetDependencies(TT, GPU, FS);
 

lib/Target/AMDGPU/Processors.td

 def : Proc<"cayman",     R600_VLIW4_Itin,
     [FeatureNorthernIslands, FeatureFP64, FeatureCaymanISA]>;
 
 //===----------------------------------------------------------------------===//
 // Southern Islands
 //===----------------------------------------------------------------------===//
 
 def : ProcessorModel<"SI", SIFullSpeedModel,
-  [FeatureSouthernIslands, FeatureFastFMAF32]
+  [FeatureSouthernIslands, FeatureFastFMAF32, HalfRate64Ops]
 >;
 
-def : ProcessorModel<"tahiti",   SIFullSpeedModel,
-  [FeatureSouthernIslands, FeatureFastFMAF32]
+def : ProcessorModel<"tahiti", SIFullSpeedModel,
+  [FeatureSouthernIslands, FeatureFastFMAF32, HalfRate64Ops]
 >;
 
 def : ProcessorModel<"pitcairn", SIQuarterSpeedModel, [FeatureSouthernIslands]>;
 
 def : ProcessorModel<"verde",    SIQuarterSpeedModel, [FeatureSouthernIslands]>;
 
 def : ProcessorModel<"oland",    SIQuarterSpeedModel, [FeatureSouthernIslands]>;
 
def : ProcessorModel<"kabini",     SIQuarterSpeedModel,
   [FeatureSeaIslands, FeatureLDSBankCount16]
 >;
 
 def : ProcessorModel<"kaveri",     SIQuarterSpeedModel,
   [FeatureSeaIslands, FeatureLDSBankCount32, FeatureISAVersion7_0_0]
 >;
 
 def : ProcessorModel<"hawaii", SIFullSpeedModel,
-  [FeatureSeaIslands, FeatureFastFMAF32, FeatureLDSBankCount32,
-   FeatureISAVersion7_0_1]
+  [FeatureSeaIslands, FeatureFastFMAF32, HalfRate64Ops,
+   FeatureLDSBankCount32, FeatureISAVersion7_0_1]
 >;
 
 def : ProcessorModel<"mullins",    SIQuarterSpeedModel,
   [FeatureSeaIslands, FeatureLDSBankCount16]>;
 
 //===----------------------------------------------------------------------===//
 // Volcanic Islands
 //===----------------------------------------------------------------------===//