test: add v128 SIMD global round-trip test for big-endian platforms

Author: guybedford

test/parallel/test-wasm-simd-global.js

@@ -0,0 +1,59 @@
+'use strict';
+
+// Test that v128 SIMD globals work correctly end-to-end on all platforms,
+// including big-endian (s390x). Specifically:
+// 1. v128.const initializer -> global.get -> i32x4.extract_lane round-trip
+// 2. i32x4.replace_lane -> global.set -> global.get -> i32x4.extract_lane round-trip
+//
+// This is a regression check for potential big-endian issues in V8's handling
+// of v128 globals (e.g. s390x), independent of the ESM import path.
+
+const common = require('../common');
+const assert = require('assert');
+
+// WAT source:
+// (module
+//   (global $g (mut v128) (v128.const i32x4 1 2 3 4))
+//   (func (export "get0") (result i32) global.get $g i32x4.extract_lane 0)
+//   (func (export "get1") (result i32) global.get $g i32x4.extract_lane 1)
+//   (func (export "get2") (result i32) global.get $g i32x4.extract_lane 2)
+//   (func (export "get3") (result i32) global.get $g i32x4.extract_lane 3)
+//   (func (export "set") (param i32 i32 i32 i32)
+//     i32.const 0 i32x4.splat
+//     local.get 0 i32x4.replace_lane 0
+//     local.get 1 i32x4.replace_lane 1
+//     local.get 2 i32x4.replace_lane 2
+//     local.get 3 i32x4.replace_lane 3
+//     global.set $g)
+// )
+const wasmBytes = new Uint8Array([
+  0, 97, 115, 109, 1, 0, 0, 0, 1, 12, 2, 96, 0, 1, 127, 96, 4, 127, 127,
+  127, 127, 0, 3, 6, 5, 0, 0, 0, 0, 1, 6, 22, 1, 123, 1, 253, 12, 1, 0, 0,
+  0, 2, 0, 0, 0, 3, 0, 0, 0, 4, 0, 0, 0, 11, 7, 35, 5, 4, 103, 101, 116, 48,
+  0, 0, 4, 103, 101, 116, 49, 0, 1, 4, 103, 101, 116, 50, 0, 2, 4, 103, 101,
+  116, 51, 0, 3, 3, 115, 101, 116, 0, 4, 10, 62, 5, 7, 0, 35, 0, 253, 27, 0,
+  11, 7, 0, 35, 0, 253, 27, 1, 11, 7, 0, 35, 0, 253, 27, 2, 11, 7, 0, 35, 0,
+  253, 27, 3, 11, 28, 0, 65, 0, 253, 17, 32, 0, 253, 28, 0, 32, 1, 253, 28,
+  1, 32, 2, 253, 28, 2, 32, 3, 253, 28, 3, 36, 0, 11, 0, 11, 4, 110, 97,
+  109, 101, 7, 4, 1, 0, 1, 103,
+]);
+
+if (!WebAssembly.validate(wasmBytes)) {
+  common.skip('WebAssembly SIMD not supported');
+}
+
+const { exports: { get0, get1, get2, get3, set } } =
+  new WebAssembly.Instance(new WebAssembly.Module(wasmBytes));
+
+// Test 1: v128.const initializer lanes are read back correctly.
+assert.strictEqual(get0(), 1, 'v128.const lane 0 should be 1');
+assert.strictEqual(get1(), 2, 'v128.const lane 1 should be 2');
+assert.strictEqual(get2(), 3, 'v128.const lane 2 should be 3');
+assert.strictEqual(get3(), 4, 'v128.const lane 3 should be 4');
+
+// Test 2: replace_lane -> global.set -> global.get -> extract_lane round-trip.
+set(10, 20, 30, 40);
+assert.strictEqual(get0(), 10, 'after set, lane 0 should be 10');
+assert.strictEqual(get1(), 20, 'after set, lane 1 should be 20');
+assert.strictEqual(get2(), 30, 'after set, lane 2 should be 30');
+assert.strictEqual(get3(), 40, 'after set, lane 3 should be 40');