[RISCV] Add T-HEAD extension support

[JojoR]

Summary

Add T-HEAD extension support
Depends on D140771

[asb]

Shouldn't there be some test changes along with this?

[JojoR]

In D149333#4315068, @asb wrote:

Shouldn't there be some test changes along with this?

Apologies for the lack of a response.
Yes, the usecase will be in next patch, we split big clang intrinsic like other vendor extension as D147935

[JojoR]

In D149333#4325875, @JojoR wrote:

In D149333#4315068, @asb wrote:

Shouldn't there be some test changes along with this?

Apologies for the lack of a response.
Yes, the usecase will be in next patch, we split big clang intrinsic like other vendor extension as D147935

@asb @craig.topper @kito-cheng Any prefer or suggestions ?

clang/include/clang/Support/RISCVVIntrinsicUtils.h

 
 // RVVRequire should be sync'ed with target features, but only
 // required features used in riscv_vector.td.
 enum RVVRequire : uint8_t {
   RVV_REQ_None = 0,
   RVV_REQ_RV64 = 1 << 0,
   RVV_REQ_FullMultiply = 1 << 1,
   RVV_REQ_Xsfvcp = 1 << 2,
+  RVV_REQ_Xtheadvdot = 1 << 3,
 
-  LLVM_MARK_AS_BITMASK_ENUM(RVV_REQ_Xsfvcp)
+  LLVM_MARK_AS_BITMASK_ENUM(RVV_REQ_Xtheadvdot)
 };
 
 // Raw RVV intrinsic info, used to expand later.
 // This struct is highly compact for minimized code size.
 struct RVVIntrinsicRecord {
   // Intrinsic name, e.g. vadd_vv
   const char *Name;
 

clang/utils/TableGen/RISCVVEmitter.cpp

for (auto *R : RV) {
     SR.Log2LMULMask = Log2LMULMask;
 
     SR.RequiredExtensions = 0;
     for (auto RequiredFeature : RequiredFeatures) {
       RVVRequire RequireExt = StringSwitch<RVVRequire>(RequiredFeature)
                                   .Case("RV64", RVV_REQ_RV64)
                                   .Case("FullMultiply", RVV_REQ_FullMultiply)
                                   .Case("Xsfvcp", RVV_REQ_Xsfvcp)
+                                  .Case("Xtheadvdot", RVV_REQ_Xtheadvdot)
                                   .Default(RVV_REQ_None);
       assert(RequireExt != RVV_REQ_None && "Unrecognized required feature?");
       SR.RequiredExtensions |= RequireExt;
     }
 
     SR.NF = NF;
     SR.HasMasked = HasMasked;
     SR.HasVL = HasVL;