[Testing] Add 'VECTOR_DENORMFLUSH_F32' unit test

Unit tests the `OPCODE_VECTOR_DENORMFLUSH` implementation in isolation.

src/xenia/cpu/testing/vector_flush_denorm_test.cc

@@ -0,0 +1,45 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2026 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include "xenia/cpu/testing/util.h"
+
+#include <cfloat>
+
+using namespace xe;
+using namespace xe::cpu;
+using namespace xe::cpu::hir;
+using namespace xe::cpu::testing;
+using xe::cpu::ppc::PPCContext;
+
+TEST_CASE("VECTOR_DENORMFLUSH_F32", "[instr]") {
+  TestFunction test([](HIRBuilder& b) {
+    StoreVR(b, 3, b.VectorDenormFlush(LoadVR(b, 4)));
+    b.Return();
+  });
+  test.Run([](PPCContext* ctx) { ctx->v[4] = vec128i(0x7fffff); },
+           [](PPCContext* ctx) {
+             auto result = ctx->v[3];
+             REQUIRE(result == vec128f(0.0f));
+           });
+  test.Run([](PPCContext* ctx) { ctx->v[4] = vec128i(0x807fffff); },
+           [](PPCContext* ctx) {
+             auto result = ctx->v[3];
+             REQUIRE(result == vec128f(-0.0f));
+           });
+  test.Run([](PPCContext* ctx) { ctx->v[4] = vec128f(FLT_MIN); },
+           [](PPCContext* ctx) {
+             auto result = ctx->v[3];
+             REQUIRE(result == vec128f(FLT_MIN));
+           });
+  test.Run([](PPCContext* ctx) { ctx->v[4] = vec128f(-FLT_MIN); },
+           [](PPCContext* ctx) {
+             auto result = ctx->v[3];
+             REQUIRE(result == vec128f(-FLT_MIN));
+           });
+}