[WebAssembly] Disable reference types in generic CPU (#90792)

#80923 newly enabled multivalue and reference-types in the generic CPU.
But enabling reference-types ended up breaking up Wasm's Chromium CI
(https://chromium-review.googlesource.com/c/emscripten-releases/+/5500231)
because the way the table index is encoded is different from MVP (u32)
vs. reference-types (LEB), which caused different encodings for
`call_indirect`.

And Chromium CI's and Emscripten's minimum required node version is v16,
which does not yet support reference-types, which does not recognize
that table index encoding. reference-types is first supported in node
v17.2.

We knew the current minimum required node for Emscripten (v16) did not
support reference-types, but thought it was fine because unless you
explicitly use `__funcref` or `__externref` things would be fine, and if
you want to use them explicitly, you would have a newer node. But it
turned out it also affected the encoding of `call_indirect`.

While we are discussing the potential solutions, I will disable
reference-types to unblock the rolls.

Author: aheejin

clang/docs/ReleaseNotes.rst

@@ -742,10 +742,10 @@ AIX Support
 WebAssembly Support
 ^^^^^^^^^^^^^^^^^^^
 
-The -mcpu=generic configuration now enables multivalue and reference-types.These
-proposals are standardized and available in all major engines. Enabling
-multivalue here only enables the language feature but does not turn on the
-multivalue ABI (this enables non-ABI uses of multivalue, like exnref).
+The -mcpu=generic configuration now enables multivalue feature, which is
+standardized and available in all major engines. Enabling multivalue here only
+enables the language feature but does not turn on the multivalue ABI (this
+enables non-ABI uses of multivalue, like exnref).
 
 AVR Support
 ^^^^^^^^^^^

clang/lib/Basic/Targets/WebAssembly.cpp

@@ -153,7 +153,6 @@ bool WebAssemblyTargetInfo::initFeatureMap(
   auto addGenericFeatures = [&]() {
     Features["multivalue"] = true;
     Features["mutable-globals"] = true;
-    Features["reference-types"] = true;
     Features["sign-ext"] = true;
   };
   auto addBleedingEdgeFeatures = [&]() {
@@ -162,6 +161,7 @@ bool WebAssemblyTargetInfo::initFeatureMap(
     Features["bulk-memory"] = true;
     Features["multimemory"] = true;
     Features["nontrapping-fptoint"] = true;
+    Features["reference-types"] = true;
     Features["tail-call"] = true;
     Features["half-precision"] = true;
     setSIMDLevel(Features, SIMD128, true);

clang/test/Preprocessor/wasm-target-features.c

@@ -164,7 +164,6 @@
 //
 // GENERIC-INCLUDE-DAG: #define __wasm_multivalue__ 1{{$}}
 // GENERIC-INCLUDE-DAG: #define __wasm_mutable_globals__ 1{{$}}
-// GENERIC-INCLUDE-DAG: #define __wasm_reference_types__ 1{{$}}
 // GENERIC-INCLUDE-DAG: #define __wasm_sign_ext__ 1{{$}}
 //
 // RUN: %clang -E -dM %s -o - 2>&1 \
@@ -181,6 +180,7 @@
 // GENERIC-NOT: #define __wasm_half_precision__ 1{{$}}
 // GENERIC-NOT: #define __wasm_multimemory__ 1{{$}}
 // GENERIC-NOT: #define __wasm_nontrapping_fptoint__ 1{{$}}
+// GENERIC-NOT: #define __wasm_reference_types__ 1{{$}}
 // GENERIC-NOT: #define __wasm_relaxed_simd__ 1{{$}}
 // GENERIC-NOT: #define __wasm_simd128__ 1{{$}}
 // GENERIC-NOT: #define __wasm_tail_call__ 1{{$}}