[mlir] Add description to amdgpu.dpp and rocdl.update.dpp

mlir/include/mlir/Dialect/AMDGPU/IR/AMDGPU.td

@@ -436,8 +436,18 @@ def AMDGPU_DPPOp : AMDGPU_Op<"dpp", [SameTypeOperands, AllTypesMatch<["result",
                   DefaultValuedAttr<BoolAttr, "false">:$bound_ctrl)> {
   let summary = "AMDGPU DPP operation";
   let description = [{
-    This operation represents DPP functionality in a GPU program.
-     DPP provides the following operations:
+    This operation represents DPP (Data-Parallel Primitives) functionality in a GPU program.
+
+    It will result in the values from `src`, permuted according to
+    the DPP attributes(`kind`, `permArgument`, `row_mask`, `bank_mask` and `bound_ctrl`).
+
+    If a lane is masked off(by EXEC mask, `row_mask`, `bank_mask`, etc) or
+    has no value to receive(for example, if the source of a lane is out of range),
+    this operation will instead produce the value of `old`.
+
+    For detail explanation of the attributes, please check the ISA Reference Guide.
+
+    DPP provides the following operations:
     - Full crossbar in a group of four (`quad_perm`)
     - Wavefront shift left by one lane (`wave_shl`)
     - Wavefront shift right by one lane (`wave_shr`)

mlir/include/mlir/Dialect/LLVMIR/ROCDLOps.td

@@ -621,6 +621,21 @@ def ROCDL_DPPUpdateOp : ROCDL_IntrOp<"update.dpp", [], [0],
   Arguments<(ins LLVM_Type:$old, LLVM_Type:$src, I32Attr:$dppCtrl, I32Attr:$rowMask,
       I32Attr:$bankMask, I1Attr:$boundCtrl)> {
   let results = (outs LLVM_Type:$res);
+  let summary = "Exchange data among lanes in a warp";
+  let description = [{
+    This operation maps to the DPP (Data-Parallel Primitives) intrinsics,
+    which allows lanes in the same warp to exchange data in their registers
+    directly following some very specific patterns.
+
+    It will result in the values from `src`, permuted according to
+    the DPP attributes(`dppCtrl`, `rowMask`, `bankMask` and `boundCtrl`).
+
+    If a lane is masked off(by EXEC mask, `rowMask`, `bankMask`, etc) or
+    has no value to receive(for example, if the source of a lane is out of range),
+    this operation will instead produce the value of `old`.
+
+    For detail explanation of the attributes, please check the ISA Reference Guide.
+  }];
   let assemblyFormat = [{
     attr-dict $old `,` $src `with` $dppCtrl `,` $rowMask `,` $bankMask `,` $boundCtrl `:` type($src)
   }];