[MLIR][Standard] Add clamp operation

[alexbatashev]

Summary

The clamp operation clamps value inside a region. If target compares less than lowerBound, lowerBound is returned. If target compares more than upperBound, uppperBound is returned. Otherwise, target is returned.

[ftynse]

Please post an RFC on discourse before adding any new operations to Standard.

[alexbatashev]

In D84011#2157829, @ftynse wrote:

Please post an RFC on discourse before adding any new operations to Standard.

Sure, here's the link: https://llvm.discourse.group/t/rfc-standard-add-std-clamp-operation/1435

[alexbatashev]

This operation can be replaced with combination of affine.min/max.

mlir/include/mlir/Dialect/StandardOps/IR/Ops.td

let description = [{
 
     // Tensor element-wise ceiling value.
     %x = ceilf %y : tensor<4x?xf8>
     ```
   }];
 }
 
 //===----------------------------------------------------------------------===//
+// ClampFOp
+//===----------------------------------------------------------------------===//
+
+def ClampFOp : Std_Op<"clampf",
+    [NoSideEffect, SameOperandsAndResultType]> {
+  let summary = "floating-point clamp operation";
+  let description = [{
+    The `clampf` operation clamps value inside a region. If target compares less
+    than lowerBound, lowerBound is returned. If target compares more than
+    upperBound, uppperBound is returned. Otherwise, target is returned.
+
+    Example:
+    ```
+    clampf %0 in (%1, %2) : f32
+    "std.clampf"(%0, %1, %2) : (f32, f32, f32) -> f32
+    ```
+  }];
+  let arguments = (ins
+    FloatLike:$target,
+    FloatLike:$lowerBound,
+    FloatLike:$upperBound
+  );
+  let results = (outs FloatLike:$result);
+
+  let verifier = [{ return success(); }];
+
+  let assemblyFormat = "$target `in` `(` $lowerBound `,` $upperBound `)`"
+                       " attr-dict `:` type($result)";
+}
+
+//===----------------------------------------------------------------------===//
+// ClampIOp
+//===----------------------------------------------------------------------===//
+
+def ClampIOp : Std_Op<"clampi",
+    [NoSideEffect, SameOperandsAndResultType]> {
+  let summary = "integer clamp operation";
+  let description = [{
+    The `clampi` operation clamps value inside a region. If target compares less
+    than lowerBound, lowerBound is returned. If target compares more than
+    upperBound, uppperBound is returned. Otherwise, target is returned.
+
+    Example:
+    ```
+    clampi %0 in (%1, %2) : i32
+    "std.clampi"(%0, %1, %2) : (i32, i32, i32) -> i32
+    ```
+  }];
+  let arguments = (ins
+    SignlessIntegerLike:$target,
+    SignlessIntegerLike:$lowerBound,
+    SignlessIntegerLike:$upperBound
+  );
+  let results = (outs SignlessIntegerLike:$result);
+
+  let verifier = [{ return success(); }];
+
+  let assemblyFormat = "$target `in` `(` $lowerBound `,` $upperBound `)`"
+                       " attr-dict `:` type($result)";
+}
+
+//===----------------------------------------------------------------------===//
 // CmpFOp
 //===----------------------------------------------------------------------===//
 
 // The predicate indicates the type of the comparison to perform:
 // (un)orderedness, (in)equality and less/greater than (or equal to) as
 // well as predicates that are always true or false.
 def CMPF_P_FALSE   : I64EnumAttrCase<"AlwaysFalse", 0, "false">;
 def CMPF_P_OEQ     : I64EnumAttrCase<"OEQ", 1, "oeq">;

mlir/test/Dialect/Standard/ops.mlir

func @test_index_cast_tensor_reverse(%arg0 : tensor<i64>) -> tensor<index> {
   %0 = index_cast %arg0 : tensor<i64> to tensor<index>
   return %0 : tensor<index>
 }
 
 func @assert(%arg : i1) {
   assert %arg, "Some message in case this assertion fails."
   return
 }
+
+func @test_clampi(%arg0 : i32, %arg1 : i32, %arg2 : i32) {
+  clampi %arg0 in (%arg1, %arg2) : i32
+  return
+}
+
+func @test_clampf(%arg0 : f32, %arg1 : f32, %arg2 : f32) {
+  clampf %arg0 in (%arg1, %arg2) : f32
+  return
+}