[ROCDL][LLVM] Added rocdl.fmed3 -> Intrinsic::amdgcn_fmed3 (llvm#159332)

## Description
Added ROCDL fmed3 op to support rewrite to `amdgcn_fmed3` intrinsic.

## Testing
- ROCDL -> LLVMIR lit tests for new `rocdl.med3` ops in
`/test/Target/LLVMIR/rocdl.mlir`

Addresses [llvm#157052](llvm#157052)

---------

Signed-off-by: keshavvinayak01 <[email protected]>

Author: keshavvinayak01

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

@@ -1360,6 +1360,37 @@ def ROCDL_CvtScaleF32PkFp4F32Op :
   }];
 }
 
+//===----------------------------------------------------------------------===//
+// FMED3 operations
+//===----------------------------------------------------------------------===//
+
+def ROCDL_FMed3Op : ROCDL_IntrOp<"fmed3", [0], [], [Pure, AllTypesMatch<["res", "src0", "src1", "src2"]>], 1>,
+  Arguments<(ins LLVM_ScalarOrVectorOf<LLVM_AnyFloat>:$src0,
+                 LLVM_ScalarOrVectorOf<LLVM_AnyFloat>:$src1,
+                 LLVM_ScalarOrVectorOf<LLVM_AnyFloat>:$src2)> {
+  let results = (outs LLVM_ScalarOrVectorOf<LLVM_AnyFloat>:$res);
+  let summary = "Median of three float/half values";
+  let description = [{
+    Computes the median of three floating-point values using the AMDGPU fmed3 intrinsic.
+    This operation is equivalent to `max(min(a, b), min(max(a, b), c))` but uses the
+    hardware-accelerated V_MED3_F16/V_MED3_F32 instruction for better performance.
+    
+    The operation supports both scalar and vector floating-point types (f16, f32).
+    
+    Example:
+    ```mlir
+    // Scalar f32 median
+    %result = rocdl.fmed3 %a, %b, %c : f32
+    
+    // Vector f16 median
+    %result = rocdl.fmed3 %va, %vb, %vc : vector<4xf16>
+    ```
+  }];
+  let assemblyFormat = [{
+    $src0 `,` $src1 `,` $src2 attr-dict `:` type($res)
+  }];
+}
+
 //===----------------------------------------------------------------------===//
 // ROCDL target attribute.
 //===----------------------------------------------------------------------===//

mlir/test/Dialect/LLVMIR/rocdl.mlir

@@ -29,6 +29,20 @@ func.func @rocdl_special_regs() -> i32 {
   llvm.return %0 : i32
 }
 
+func.func @rocdl.fmed3.scalar(%a: f32, %b: f32, %c: f32) -> f32 {
+  // CHECK-LABEL: rocdl.fmed3.scalar
+  // CHECK: %0 = rocdl.fmed3 %arg0, %arg1, %arg2 : f32
+  %0 = rocdl.fmed3 %a, %b, %c : f32
+  llvm.return %0 : f32
+}
+
+func.func @rocdl.fmed3.vector(%a: vector<4xf16>, %b: vector<4xf16>, %c: vector<4xf16>) -> vector<4xf16> {
+  // CHECK-LABEL: rocdl.fmed3.vector
+  // CHECK: %0 = rocdl.fmed3 %arg0, %arg1, %arg2 : vector<4xf16>
+  %0 = rocdl.fmed3 %a, %b, %c : vector<4xf16>
+  llvm.return %0 : vector<4xf16>
+}
+
 func.func @rocdl.barrier() {
   // CHECK: rocdl.barrier
   rocdl.barrier

mlir/test/Target/LLVMIR/rocdl.mlir

@@ -1298,6 +1298,20 @@ llvm.func @rocdl_last_use(%ptr: !llvm.ptr<1>) -> i32 {
   llvm.return %ret : i32
 }
 
+llvm.func @test_fmed3_f16(%arg0: f16, %arg1: f16, %arg2: f16) -> f16 {
+  // CHECK-LABEL: define half @test_fmed3_f16(half %0, half %1, half %2)
+  %0 = rocdl.fmed3 %arg0, %arg1, %arg2 : f16
+  llvm.return %0 : f16
+  // CHECK: call half @llvm.amdgcn.fmed3.f16(half %0, half %1, half %2)
+}
+
+llvm.func @test_fmed3_f32(%arg0: f32, %arg1: f32, %arg2: f32) -> f32 {
+  // CHECK-LABEL: define float @test_fmed3_f32(float %0, float %1, float %2)
+  %0 = rocdl.fmed3 %arg0, %arg1, %arg2 : f32
+  llvm.return %0 : f32
+  // CHECK: call float @llvm.amdgcn.fmed3.f32(float %0, float %1, float %2)
+}
+
 // CHECK-LABEL: rocdl.cvt.scale.pk8
 // CHECK-SAME:(i32 %[[I32:.+]], <2 x i32> %[[V2I32:.+]], i32 %[[SCALE:.+]])
 llvm.func @rocdl.cvt.scale.pk8(%i32: i32, %v2xi32: vector<2xi32>, %scale: i32) {