[RISCV] Lazily add RVV C intrinsics.

Leverage the method OpenCL uses that adds C intrinsics when the lookup
failed. There is no need to define C intrinsics in the header file any
more. It could help to avoid the large header file to speed up the
compilation of RVV source code. Besides that, only the C intrinsics used
by the users will be added into the declaration table.

This patch is based on https://reviews.llvm.org/D103228 and inspired by
OpenCL implementation.

### Experimental Results

#### TL;DR:

- Binary size of clang increase ~200k, which is +0.07%  for debug build and +0.13% for release build.
- Single file compilation speed up ~33x for debug build and ~8.5x for release build
- Regression time reduce ~10% (`ninja check-all`, enable all targets)

#### Header size change
```
       |      size |     LoC |
------------------------------
Before | 4,434,725 |  69,749 |
After  |     6,140 |     162 |
```

#### Single File Compilation Time
Testcase:
```
#include <riscv_vector.h>

vint32m1_t test_vadd_vv_vfloat32m1_t(vint32m1_t op1, vint32m1_t op2, size_t vl) {
  return vadd(op1, op2, vl);
}
```
##### Debug build:
Before:
```
real    0m19.352s
user    0m19.252s
sys     0m0.092s
```

After:
```
real    0m0.576s
user    0m0.552s
sys     0m0.024s
```

~33x speed up for debug build

##### Release build:
Before:
```
real    0m0.773s
user    0m0.741s
sys     0m0.032s
```

After:
```
real    0m0.092s
user    0m0.080s
sys     0m0.012s
```

~8.5x speed up for release build

#### Regression time
Note: the failed case is `tools/llvm-debuginfod-find/debuginfod.test` which is unrelated to this patch.

##### Debug build
Before:
```
Testing Time: 1358.38s
  Skipped          :    11
  Unsupported      :   446
  Passed           : 75767
  Expectedly Failed:   190
  Failed           :     1
```
After
```
Testing Time: 1220.29s
  Skipped          :    11
  Unsupported      :   446
  Passed           : 75767
  Expectedly Failed:   190
  Failed           :     1
```
##### Release build
Before:
```
Testing Time: 381.98s
  Skipped          :    12
  Unsupported      :  1407
  Passed           : 74765
  Expectedly Failed:   176
  Failed           :     1
```
After:
```
Testing Time: 346.25s
  Skipped          :    12
  Unsupported      :  1407
  Passed           : 74765
  Expectedly Failed:   176
  Failed           :     1
```

#### Binary size of clang

##### Debug build
Before
```
   text    data     bss     dec     hex filename
335261851       12726004         552812 348540667       14c64efb        bin/clang
```
After
```
   text    data     bss     dec     hex filename
335442803       12798708         552940 348794451       14ca2e53        bin/clang
```
+253K, +0.07% code size

##### Release build
Before
```
   text    data     bss     dec     hex filename
144123975       8374648  483140 152981763       91e5103 bin/clang
```
After
```
   text    data     bss     dec     hex filename
144255762       8447296  483268 153186326       9217016 bin/clang
```
+204K, +0.13%

Authored-by: Kito Cheng <kito.cheng@sifive.com>
Co-Authored-by: Hsiangkai Wang <kai.wang@sifive.com>

Reviewed By: khchen, aaron.ballman

Differential Revision: https://reviews.llvm.org/D111617

1 files changed, 6 insertions, 0 deletions

diff --git a/clang/utils/TableGen/TableGen.cpp b/clang/utils/TableGen/TableGen.cpp
index bb9366e..d18a312 100644
--- a/clang/utils/TableGen/TableGen.cpp
+++ b/clang/utils/TableGen/TableGen.cpp
@@ -88,6 +88,7 @@ enum ActionType {
   GenRISCVVectorHeader,
   GenRISCVVectorBuiltins,
   GenRISCVVectorBuiltinCG,
+  GenRISCVVectorBuiltinSema,
   GenAttrDocs,
   GenDiagDocs,
   GenOptDocs,
@@ -243,6 +244,8 @@ cl::opt<ActionType> Action(
                    "Generate riscv_vector_builtins.inc for clang"),
         clEnumValN(GenRISCVVectorBuiltinCG, "gen-riscv-vector-builtin-codegen",
                    "Generate riscv_vector_builtin_cg.inc for clang"),
+        clEnumValN(GenRISCVVectorBuiltinSema, "gen-riscv-vector-builtin-sema",
+                   "Generate riscv_vector_builtin_sema.inc for clang"),
         clEnumValN(GenAttrDocs, "gen-attr-docs",
                    "Generate attribute documentation"),
         clEnumValN(GenDiagDocs, "gen-diag-docs",
@@ -458,6 +461,9 @@ bool ClangTableGenMain(raw_ostream &OS, RecordKeeper &Records) {
   case GenRISCVVectorBuiltinCG:
     EmitRVVBuiltinCG(Records, OS);
     break;
+  case GenRISCVVectorBuiltinSema:
+    EmitRVVBuiltinSema(Records, OS);
+    break;
   case GenAttrDocs:
     EmitClangAttrDocs(Records, OS);
     break;