[llvm][RISCV] Support RISCV vector tuple type in llvm IR (#97992)

Summary:
This patch proposes new llvm types for RISCV vector tuples represented
as `TargetExtType` which contains both `LMUL` and `NF`(num_fields)
information and keep it all the way down to `selectionDAG` to match the
corresponding `MVT`(support in the following patch).

Detail:
Currently we have built-in C types for RISCV vector tuple type, e.g.
`vint32m1x2_t`, however it's is represented as structure of scalable
vector types, i.e. `{<vscale x 2 x i32>, <vscale x 2 x i32>}`. It loses
the information for num_fields(NF) as struct is flattened during
`selectionDAG`, thus it makes it not possible to handle inline assembly
of vector tuple type, it also makes the calling convention of vector
tuple types handing not strait forward and hard to realize the
allocation code, i.e. `RVVArgDispatcher`.

The llvm IR for the example above is then represented as
`target("riscv.vector.tuple", <vscale x 8 x i8>, 2)` in which the first
type parameter is the equivalent size scalable vecotr of i8 element
type, the following integer parameter is the `NF` of the tuple.

The new RISCV specific vector insert/extract intrinsics are also added
as `llvm.riscv.vector.insert` and `llvm.riscv.vector.extract` to handle
tuple type subvector insertion/extraction since the generic ones only
operates on `VectorType` but not `TargetExtType`.

There are total of 32 llvm types added for each `VREGS * NF <= 8`, where
`VREGS` is the vector registers needed for each `LMUL` and `NF` is
num_fields.
The name of types are:
```
target("riscv.vector.tuple", <vscale x 1 x i8>, 2)  // LMUL = mf8, NF = 2
target("riscv.vector.tuple", <vscale x 1 x i8>, 3)  // LMUL = mf8, NF = 3
target("riscv.vector.tuple", <vscale x 1 x i8>, 4)  // LMUL = mf8, NF = 4
target("riscv.vector.tuple", <vscale x 1 x i8>, 5)  // LMUL = mf8, NF = 5
target("riscv.vector.tuple", <vscale x 1 x i8>, 6)  // LMUL = mf8, NF = 6
target("riscv.vector.tuple", <vscale x 1 x i8>, 7)  // LMUL = mf8, NF = 7
target("riscv.vector.tuple", <vscale x 1 x i8>, 8)  // LMUL = mf8, NF = 8
target("riscv.vector.tuple", <vscale x 2 x i8>, 2)  // LMUL = mf4, NF = 2
target("riscv.vector.tuple", <vscale x 2 x i8>, 3)  // LMUL = mf4, NF = 3
target("riscv.vector.tuple", <vscale x 2 x i8>, 4)  // LMUL = mf4, NF = 4
target("riscv.vector.tuple", <vscale x 2 x i8>, 5)  // LMUL = mf4, NF = 5
target("riscv.vector.tuple", <vscale x 2 x i8>, 6)  // LMUL = mf4, NF = 6
target("riscv.vector.tuple", <vscale x 2 x i8>, 7)  // LMUL = mf4, NF = 7
target("riscv.vector.tuple", <vscale x 2 x i8>, 8)  // LMUL = mf4, NF = 8
target("riscv.vector.tuple", <vscale x 4 x i8>, 2)  // LMUL = mf2, NF = 2
target("riscv.vector.tuple", <vscale x 4 x i8>, 3)  // LMUL = mf2, NF = 3
target("riscv.vector.tuple", <vscale x 4 x i8>, 4)  // LMUL = mf2, NF = 4
target("riscv.vector.tuple", <vscale x 4 x i8>, 5)  // LMUL = mf2, NF = 5
target("riscv.vector.tuple", <vscale x 4 x i8>, 6)  // LMUL = mf2, NF = 6
target("riscv.vector.tuple", <vscale x 4 x i8>, 7)  // LMUL = mf2, NF = 7
target("riscv.vector.tuple", <vscale x 4 x i8>, 8)  // LMUL = mf2, NF = 8
target("riscv.vector.tuple", <vscale x 8 x i8>, 2)  // LMUL = m1, NF = 2
target("riscv.vector.tuple", <vscale x 8 x i8>, 3)  // LMUL = m1, NF = 3
target("riscv.vector.tuple", <vscale x 8 x i8>, 4)  // LMUL = m1, NF = 4
target("riscv.vector.tuple", <vscale x 8 x i8>, 5)  // LMUL = m1, NF = 5
target("riscv.vector.tuple", <vscale x 8 x i8>, 6)  // LMUL = m1, NF = 6
target("riscv.vector.tuple", <vscale x 8 x i8>, 7)  // LMUL = m1, NF = 7
target("riscv.vector.tuple", <vscale x 8 x i8>, 8)  // LMUL = m1, NF = 8
target("riscv.vector.tuple", <vscale x 16 x i8>, 2) // LMUL = m2, NF = 2
target("riscv.vector.tuple", <vscale x 16 x i8>, 3) // LMUL = m2, NF = 3
target("riscv.vector.tuple", <vscale x 16 x i8>, 4) // LMUL = m2, NF = 4
target("riscv.vector.tuple", <vscale x 32 x i8>, 2) // LMUL = m4, NF = 2
```

RFC:
https://discourse.llvm.org/t/rfc-support-riscv-vector-tuple-type-in-llvm/80005

Author: 4vtomat

clang/include/clang/Basic/riscv_vector.td

@@ -428,6 +428,7 @@ class RVVIntrinsic {
   bool hasBuiltinAlias() const { return HasBuiltinAlias; }
   bool hasManualCodegen() const { return !ManualCodegen.empty(); }
   bool isMasked() const { return IsMasked; }
+  llvm::StringRef getOverloadedName() const { return OverloadedName; }
   llvm::StringRef getIRName() const { return IRName; }
   llvm::StringRef getManualCodegen() const { return ManualCodegen; }
   PolicyScheme getPolicyScheme() const { return Scheme; }