[dev.simd] simd: reorganize internal tests so that simd does not import testing

Change-Id: Id68835fd8f93d2252a072132ff1b8ee39f197977
Reviewed-on: https://go-review.googlesource.com/c/go/+/721940
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

Author: dr2chase

src/simd/export_test.go

@@ -0,0 +1,64 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build goexperiment.simd && amd64
+
+// This exposes some internal interfaces to simd_test.
+
+package simd
+
+func (x Int64x2) ExportTestConcatSelectedConstant(indices uint8, y Int64x2) Int64x2 {
+	return x.concatSelectedConstant(indices, y)
+}
+
+func (x Float64x4) ExportTestConcatSelectedConstantGrouped(indices uint8, y Float64x4) Float64x4 {
+	return x.concatSelectedConstantGrouped(indices, y)
+}
+
+func (x Float32x4) ExportTestConcatSelectedConstant(indices uint8, y Float32x4) Float32x4 {
+	return x.concatSelectedConstant(indices, y)
+}
+
+func (x Int32x4) ExportTestConcatSelectedConstant(indices uint8, y Int32x4) Int32x4 {
+	return x.concatSelectedConstant(indices, y)
+}
+
+func (x Uint32x8) ExportTestConcatSelectedConstantGrouped(indices uint8, y Uint32x8) Uint32x8 {
+	return x.concatSelectedConstantGrouped(indices, y)
+}
+
+func (x Int32x8) ExportTestConcatSelectedConstantGrouped(indices uint8, y Int32x8) Int32x8 {
+	return x.concatSelectedConstantGrouped(indices, y)
+}
+
+func (x Int32x8) ExportTestTern(table uint8, y Int32x8, z Int32x8) Int32x8 {
+	return x.tern(table, y, z)
+}
+
+func (x Int32x4) ExportTestTern(table uint8, y Int32x4, z Int32x4) Int32x4 {
+	return x.tern(table, y, z)
+}
+
+func ExportTestCscImm4(a, b, c, d uint8) uint8 {
+	return cscimm4(a, b, c, d)
+}
+
+const (
+	LLLL = _LLLL
+	HLLL = _HLLL
+	LHLL = _LHLL
+	HHLL = _HHLL
+	LLHL = _LLHL
+	HLHL = _HLHL
+	LHHL = _LHHL
+	HHHL = _HHHL
+	LLLH = _LLLH
+	HLLH = _HLLH
+	LHLH = _LHLH
+	HHLH = _HHLH
+	LLHH = _LLHH
+	HLHH = _HLHH
+	LHHH = _LHHH
+	HHHH = _HHHH
+)