[WebAssembly] Enable nontrapping-fptoint and bulk-memory by default.

We were prepared to enable these features [back in February], but they
got pulled for what appear to be unrelated reasons. So let's have another
try at enabling them!

Another motivation here is that it'd be convenient for the
[Trail1 proposal] if "trail1" is a superset of "generic".

[back in February]: WebAssembly/tool-conventions#158 (comment)
[Trail1 proposal]: llvm#112035

clang/docs/ReleaseNotes.rst

@@ -627,6 +627,15 @@ NetBSD Support
 WebAssembly Support
 ^^^^^^^^^^^^^^^^^^^
 
+The default target CPU, "generic", now enables the `-mnontrapping-fptoint`
+and `-mbulk-memory` flags, which correspond to the [Bulk Memory Operations]
+and [Non-trapping float-to-int Conversions] language features, which are
+[widely implemented in engines].
+
+[Bulk Memory Operations]: https://github.com/WebAssembly/bulk-memory-operations/blob/master/proposals/bulk-memory-operations/Overview.md
+[Non-trapping float-to-int Conversions]: https://github.com/WebAssembly/spec/blob/master/proposals/nontrapping-float-to-int-conversion/Overview.md
+[widely implemented in engines]: https://webassembly.org/features/
+
 AVR Support
 ^^^^^^^^^^^
 

clang/lib/Basic/Targets/WebAssembly.cpp

@@ -151,8 +151,10 @@ bool WebAssemblyTargetInfo::initFeatureMap(
     llvm::StringMap<bool> &Features, DiagnosticsEngine &Diags, StringRef CPU,
     const std::vector<std::string> &FeaturesVec) const {
   auto addGenericFeatures = [&]() {
+    Features["bulk-memory"] = true;
     Features["multivalue"] = true;
     Features["mutable-globals"] = true;
+    Features["nontrapping-fptoint"] = true;
     Features["reference-types"] = true;
     Features["sign-ext"] = true;
   };

llvm/docs/ReleaseNotes.md

@@ -164,6 +164,15 @@ Changes to the RISC-V Backend
 Changes to the WebAssembly Backend
 ----------------------------------
 
+The default target CPU, "generic", now enables the `-mnontrapping-fptoint`
+and `-mbulk-memory` flags, which correspond to the [Bulk Memory Operations]
+and [Non-trapping float-to-int Conversions] language features, which are
+[widely implemented in engines].
+
+[Bulk Memory Operations]: https://github.com/WebAssembly/bulk-memory-operations/blob/master/proposals/bulk-memory-operations/Overview.md
+[Non-trapping float-to-int Conversions]: https://github.com/WebAssembly/spec/blob/master/proposals/nontrapping-float-to-int-conversion/Overview.md
+[widely implemented in engines]: https://webassembly.org/features/
+
 Changes to the Windows Target
 -----------------------------
 

llvm/lib/Target/WebAssembly/WebAssembly.td

@@ -110,7 +110,8 @@ def : ProcessorModel<"mvp", NoSchedModel, []>;
 // consideration given to available support in relevant engines and tools, and
 // the importance of the features.
 def : ProcessorModel<"generic", NoSchedModel,
-                      [FeatureMultivalue, FeatureMutableGlobals,
+                      [FeatureBulkMemory, FeatureMultivalue,
+                       FeatureMutableGlobals, FeatureNontrappingFPToInt,
                        FeatureReferenceTypes, FeatureSignExt]>;
 
 // Latest and greatest experimental version of WebAssembly. Bugs included!