[mlir][spirv] Fix links in docs and update dialect docs

[antiagainst]

Summary

This commit fixes links to code directories and uses doc links on
mlir.llvm.org where possible. The docs in TableGen dialect definition
is also updated to reflect recent developments.

[merge_guards_bot]

Unit tests: pass. 61168 tests passed, 0 failed and 728 were skipped.

clang-tidy: fail. Please fix clang-tidy findings.

clang-format: pass.

Build artifacts: diff.json, clang-tidy.txt, clang-format.patch, CMakeCache.txt, console-log.txt, test-results.xml

mlir/docs/Dialects/SPIR-V.md

 %1 = OpExtInst %f32 %glsl 28 %cst
 %2 = OpExtInst %f32 %glsl 31 %cst
 ```
 
 we can have
 
 ```mlir
 %1 = "spv.GLSL.Log"(%cst) : (f32) -> (f32)
-%2 = "spv.GLSL.Sqrt(%cst) : (f32) -> (f32)
+%2 = "spv.GLSL.Sqrt"(%cst) : (f32) -> (f32)
 ```
 
 ## Control Flow
 
 SPIR-V binary format uses merge instructions (`OpSelectionMerge` and
 `OpLoopMerge`) to declare structured control flow. They explicitly declare a
 header block before the control flow diverges and a merge block where control
 flow subsequently converges. These blocks delimit constructs that must nest, and

 [SpirvGrammar]: https://raw.githubusercontent.com/KhronosGroup/SPIRV-Headers/master/include/spirv/unified1/spirv.core.grammar.json
 [GlslStd450]: https://www.khronos.org/registry/spir-v/specs/1.0/GLSL.std.450.html
 [ArrayType]: https://www.khronos.org/registry/spir-v/specs/unified1/SPIRV.html#OpTypeArray
 [ImageType]: https://www.khronos.org/registry/spir-v/specs/unified1/SPIRV.html#OpTypeImage
 [PointerType]: https://www.khronos.org/registry/spir-v/specs/unified1/SPIRV.html#OpTypePointer
 [RuntimeArrayType]: https://www.khronos.org/registry/spir-v/specs/unified1/SPIRV.html#OpTypeRuntimeArray
 [StructType]: https://www.khronos.org/registry/spir-v/specs/unified1/SPIRV.html#Structure
 [SpirvTools]: https://github.com/KhronosGroup/SPIRV-Tools
-[Rationale]: https://github.com/llvm/llvm-project/blob/master/mlir/docs/Rationale.md#block-arguments-vs-phi-nodes
-[ODS]: https://github.com/llvm/llvm-project/blob/master/mlir/docs/OpDefinitions.md
+[Rationale]: https://mlir.llvm.org/docs/Rationale/#block-arguments-vs-phi-nodes
+[ODS]: https://mlir.llvm.org/docs/OpDefinitions/
 [GreedyPatternRewriter]: https://github.com/llvm/llvm-project/blob/master/mlir/lib/Transforms/Utils/GreedyPatternRewriteDriver.cpp
-[MlirSpirvHeaders]: https://github.com/tensorflow/mlir/tree/master/include/mlir/Dialect/SPIRV
-[MlirSpirvLibs]: https://github.com/tensorflow/mlir/tree/master/lib/Dialect/SPIRV
-[MlirSpirvTests]: https://github.com/tensorflow/mlir/tree/master/test/Dialect/SPIRV
-[MlirSpirvUnittests]: https://github.com/tensorflow/mlir/tree/master/unittests/Dialect/SPIRV
-[MlirGpuToSpirvHeaders]: https://github.com/tensorflow/mlir/tree/master/include/mlir/Conversion/GPUToSPIRV
-[MlirGpuToSpirvLibs]: https://github.com/tensorflow/mlir/tree/master/lib/Conversion/GPUToSPIRV
-[MlirStdToSpirvHeaders]: https://github.com/tensorflow/mlir/tree/master/include/mlir/Conversion/StandardToSPIRV
-[MlirStdToSpirvLibs]: https://github.com/tensorflow/mlir/tree/master/lib/Conversion/StandardToSPIRV
+[MlirSpirvHeaders]: https://github.com/llvm/llvm-project/tree/master/mlir/include/mlir/Dialect/SPIRV
+[MlirSpirvLibs]: https://github.com/llvm/llvm-project/tree/master/mlir/lib/Dialect/SPIRV
+[MlirSpirvTests]: https://github.com/llvm/llvm-project/tree/master/mlir/test/Dialect/SPIRV
+[MlirSpirvUnittests]: https://github.com/llvm/llvm-project/tree/master/mlir/unittests/Dialect/SPIRV
+[MlirGpuToSpirvHeaders]: https://github.com/llvm/llvm-project/tree/master/mlir/include/mlir/Conversion/GPUToSPIRV
+[MlirGpuToSpirvLibs]: https://github.com/llvm/llvm-project/tree/master/mlir/lib/Conversion/GPUToSPIRV
+[MlirStdToSpirvHeaders]: https://github.com/llvm/llvm-project/tree/master/mlir/include/mlir/Conversion/StandardToSPIRV
+[MlirStdToSpirvLibs]: https://github.com/llvm/llvm-project/tree/master/mlir/lib/Conversion/StandardToSPIRV
 [MlirSpirvDialect]: https://github.com/llvm/llvm-project/blob/master/mlir/include/mlir/Dialect/SPIRV/SPIRVDialect.h
 [MlirSpirvTypes]: https://github.com/llvm/llvm-project/blob/master/mlir/include/mlir/Dialect/SPIRV/SPIRVTypes.h
 [MlirSpirvOpsH]: https://github.com/llvm/llvm-project/blob/master/mlir/include/mlir/Dialect/SPIRV/SPIRVOps.h
 [MlirSpirvSerialization]: https://github.com/llvm/llvm-project/blob/master/mlir/include/mlir/Dialect/SPIRV/Serialization.h
 [MlirSpirvBase]: https://github.com/llvm/llvm-project/blob/master/mlir/include/mlir/Dialect/SPIRV/SPIRVBase.td
 [MlirSpirvPasses]: https://github.com/llvm/llvm-project/blob/master/mlir/include/mlir/Dialect/SPIRV/Passes.h
 [MlirSpirvLowering]: https://github.com/llvm/llvm-project/blob/master/mlir/include/mlir/Dialect/SPIRV/SPIRVLowering.h
 [MlirSpirvAbi]: https://github.com/llvm/llvm-project/blob/master/mlir/include/mlir/Dialect/SPIRV/SPIRVLowering.td
 [MlirSpirvOpsCpp]: https://github.com/llvm/llvm-project/blob/master/mlir/lib/Dialect/SPIRV/SPIRVOps.cpp
 [GitHubDialectTracking]: https://github.com/tensorflow/mlir/issues/302
 [GitHubLoweringTracking]: https://github.com/tensorflow/mlir/issues/303
 [GenSpirvUtilsPy]: https://github.com/llvm/llvm-project/blob/master/mlir/utils/spirv/gen_spirv_dialect.py
 [LlvmMlirSpirvDoc]: https://mlir.llvm.org/docs/Dialects/SPIRVOps/
-[CustomTypeAttrTutorial]: https://github.com/llvm/llvm-project/blob/master/mlir/docs/DefiningAttributesAndTypes.md
+[CustomTypeAttrTutorial]: https://mlir.llvm.org/docs/DefiningAttributesAndTypes/

mlir/include/mlir/Dialect/SPIRV/SPIRVBase.td

 
 //===----------------------------------------------------------------------===//
 // SPIR-V dialect definitions
 //===----------------------------------------------------------------------===//
 
 def SPV_Dialect : Dialect {
   let name = "spv";
 
-  let description = [{
-    The SPIR-V dialect in MLIR.
+  let summary = "The SPIR-V dialect in MLIR.";
 
-    SPIR-V is the Khronos Group's binary intermediate language for representing
-    graphical-shader stages and compute kernels for multiple Khronos APIs,
-    including OpenCL, OpenGL, and Vulkan.
-    See https://www.khronos.org/registry/spir-v for more details.
-
-    This dialect aims to be a simple proxy for the SPIR-V binary format to
-    enable straightforward and lightweight conversion from/to the binary
-    format. Ops in this dialect should stay at the same semantic level and
-    try to be a mechanical mapping to the corresponding SPIR-V instructions;
-    but they may deviate representationally to allow using MLIR mechanisms.
-    As a convention, if such deviation happens, the op name follows "snake_case"
-    style; otherwise, the op name just follows the SPIR-V mnemonic (by removing
-    the leading `Op` prefix) to use "CamelCase" style.
+  let description = [{
+    SPIR-V is a binary intermediate language for representing graphical-shader
+    stages and compute kernels for multiple Khronos APIs, including OpenCL,
+    OpenGL, and Vulkan.
+    See https://www.khronos.org/registry/spir-v for more details regarding
+    SPIR-V itself.
+
+    The SPIR-V dialect aims to be a proper compiler intermediate representation
+    to faciliate transformations. Ops in this dialect stay at the same semantic
+    level as the SPIR-V specification and try to have one-to-one mapping to the
+    corresponding SPIR-V instructions; but they may deviate representationally
+    to utilize MLIR mechanisms if it results in better representation and thus
+    benefits transformations. The dialect also aims to maintain straightforward
+    serialization into and deserialization from the SPIR-V binary format.
+    See https://mlir.llvm.org/docs/Dialects/SPIR-V/ for more details regarding
+    high-level designs and implementation structures of the SPIR-V dialect.
   }];
 
   let cppNamespace = "spirv";
 }
 
 //===----------------------------------------------------------------------===//
 // SPIR-V availability definitions
 //===----------------------------------------------------------------------===//