Disable SIMD for PPC64 architecture, add UNDICI_NO_WASM_SIMD env to facilitate testing (#4530)

* Disable SIMD for PPC64 architecture, add UNDICI_NO_WASM_SIMD env to facilitate testing

Signed-off-by: Matteo Collina <[email protected]>

* fixup

Signed-off-by: Matteo Collina <[email protected]>

* fixup

Signed-off-by: Matteo Collina <[email protected]>

* fixup

Signed-off-by: Matteo Collina <[email protected]>

* Update lib/dispatcher/client-h1.js

Co-authored-by: Aras Abbasi <[email protected]>

* Apply suggestions from code review

---------

Signed-off-by: Matteo Collina <[email protected]>
Co-authored-by: Aras Abbasi <[email protected]>

Author: mcollina

lib/dispatcher/client-h1.js

@@ -64,11 +64,26 @@ function lazyllhttp () {
   const llhttpWasmData = process.env.JEST_WORKER_ID ? require('../llhttp/llhttp-wasm.js') : undefined
 
   let mod
-  try {
-    mod = new WebAssembly.Module(require('../llhttp/llhttp_simd-wasm.js'))
-  } catch {
-    /* istanbul ignore next */
 
+  // We disable wasm SIMD on ppc64 as it seems to be broken on Power 9 architectures.
+  let useWasmSIMD = process.arch !== 'ppc64'
+  // The Env Variable UNDICI_NO_WASM_SIMD allows explicitly overriding the default behavior
+  if (process.env.UNDICI_NO_WASM_SIMD === '1') {
+    useWasmSIMD = true
+  } else if (process.env.UNDICI_NO_WASM_SIMD === '0') {
+    useWasmSIMD = false
+  }
+
+  if (useWasmSIMD) {
+    try {
+      mod = new WebAssembly.Module(require('../llhttp/llhttp_simd-wasm.js'))
+      /* istanbul ignore next */
+    } catch {
+    }
+  }
+
+  /* istanbul ignore next */
+  if (!mod) {
     // We could check if the error was caused by the simd option not
     // being enabled, but the occurring of this other error
     // * https://github.com/emscripten-core/emscripten/issues/11495