[WebAssembly] Update supported features in -mcpu=generic

[sunfish]

Summary

Enable nontrapping-fptoint, sign-ext, bulk-memory, and mutable-globals in -mcpu=generic. This makes these features enabled by default.

These features are all [finished proposals], and all major wasm engines support them.

[finished proposals]: https://github.com/WebAssembly/proposals/blob/main/finished-proposals.md

[asb]

Based on the discussion we had, I think this makes sense. It's a bit repetitive, but could you please add a test to clang/test/Driver that checks the list of enabled features for generic (and for completeness, probably bleeding-edge as well). Thanks.

[asb]

Oh, and per recent updates to the LLVM Developer policy I think it would be worth updating the Clang ReleaseNotes.rst to mention this change.

[sunfish]

Add a driver test, and add release notes.

[sunfish]

Add tests for -mcpu=mvp and -mcpu=bleeding-edge.

[asb]

One thing that's not ideal about this test case is that it still passes if you delete the changes to WebAssembly.cpp. At least for RISC-V, selecting the -mcpu also emits the relevant -target-feature +foo for features supported by that CPU, which doesn't seem to happen here. Haven't been able to trace through to see if that's due to us doing something obviously different in the RISC-V case.

[sbc100]

Do you think we should backport this to llvm 15, since it missed the branch point?

[sbc100]

Emscripten-side change in preparation for this to land: https://github.com/emscripten-core/emscripten/pull/17689

clang/docs/ReleaseNotes.rst

 - Fix 32-bit ``__fastcall`` and ``__vectorcall`` ABI mismatch with MSVC.
 - Add ISA of ``AMX-FP16`` which support ``_tile_dpfp16ps``.
 - Switch ``AVX512-BF16`` intrinsics types from ``short`` to ``__bf16``.
 - Add support for ``PREFETCHI`` instructions.
 - Support ISA of ``CMPCCXADD``.
   * Support intrinsic of ``__cmpccxadd_epi32``.
   * Support intrinsic of ``__cmpccxadd_epi64``.
 
+WebAssembly Support in Clang
+----------------------------
+
+The -mcpu=generic configuration now enables sign-ext and mutable-globals. These
+proposals are standardized and available in all major engines.
+
 DWARF Support in Clang
 ----------------------
 
 Arm and AArch64 Support in Clang
 --------------------------------
 
 - The target(..) function attributes for AArch64 now accept:
 

clang/lib/Basic/Targets/WebAssembly.cpp

bool WebAssemblyTargetInfo::initFeatureMap(
   if (CPU == "bleeding-edge") {
     Features["nontrapping-fptoint"] = true;
     Features["sign-ext"] = true;
     Features["bulk-memory"] = true;
     Features["atomics"] = true;
     Features["mutable-globals"] = true;
     Features["tail-call"] = true;
     setSIMDLevel(Features, SIMD128, true);
+  } else if (CPU == "generic") {
+    Features["sign-ext"] = true;
+    Features["mutable-globals"] = true;
   }
 
   return TargetInfo::initFeatureMap(Features, Diags, CPU, FeaturesVec);
 }
 
 bool WebAssemblyTargetInfo::handleTargetFeatures(
     std::vector<std::string> &Features, DiagnosticsEngine &Diags) {
   for (const auto &Feature : Features) {

clang/test/Driver/wasm-features.c

+// RUN: %clang --target=wasm32-unknown-unknown -### %s -fsyntax-only 2>&1 | FileCheck %s
+
+// CHECK: "-fvisibility=hidden"
+
+// RUN: %clang --target=wasm32-unknown-unknown -### %s 2>&1 | FileCheck %s -check-prefix=DEFAULT
+// RUN: %clang --target=wasm32-unknown-unknown -### %s -mcpu=mvp 2>&1 | FileCheck %s -check-prefix=MVP
+// RUN: %clang --target=wasm32-unknown-unknown -### %s -mcpu=bleeding-edge 2>&1 | FileCheck %s -check-prefix=BLEEDING-EDGE
+
+// RUN: %clang --target=wasm32-unknown-unknown -### %s -mbulk-memory 2>&1 | FileCheck %s -check-prefix=BULK-MEMORY
+// RUN: %clang --target=wasm32-unknown-unknown -### %s -mno-bulk-memory 2>&1 | FileCheck %s -check-prefix=NO-BULK-MEMORY
+
+// BULK-MEMORY: "-target-feature" "+bulk-memory"
+// NO-BULK-MEMORY: "-target-feature" "-bulk-memory"
+// DEFAULT-NOT: "-target-feature" "-bulk-memory"
+// MVP-NOT: "-target-feature" "+bulk-memory"
+// BLEEDING-EDGE-NOT: "-target-feature" "-bulk-memory"
+
+// RUN: %clang --target=wasm32-unknown-unknown -### %s -mmutable-globals 2>&1 | FileCheck %s -check-prefix=MUTABLE-GLOBALS
+// RUN: %clang --target=wasm32-unknown-unknown -### %s -mno-mutable-globals 2>&1 | FileCheck %s -check-prefix=NO-MUTABLE-GLOBALS
+
+// MUTABLE-GLOBALS: "-target-feature" "+mutable-globals"
+// NO-MUTABLE-GLOBALS: "-target-feature" "-mutable-globals"
+// DEFAULT-NOT: "-target-feature" "-mutable-globals"
+// MVP-NOT: "-target-feature" "+mutable-globals"
+// BLEEDING-EDGE-NOT: "-target-feature" "-mutable-globals"
+
+// RUN: %clang --target=wasm32-unknown-unknown -### %s -msign-ext 2>&1 | FileCheck %s -check-prefix=SIGN-EXT
+// RUN: %clang --target=wasm32-unknown-unknown -### %s -mno-sign-ext 2>&1 | FileCheck %s -check-prefix=NO-SIGN-EXT
+
+// SIGN-EXT: "-target-feature" "+sign-ext"
+// NO-SIGN-EXT: "-target-feature" "-sign-ext"
+// DEFAULT-NOT: "-target-feature" "-sign-ext"
+// MVP-NOT: "-target-feature" "+sign-ext"
+// BLEEDING-EDGE-NOT: "-target-feature" "-sign-ext"
+
+// RUN: %clang --target=wasm32-unknown-unknown -### %s -mnontrapping-fptoint 2>&1 | FileCheck %s -check-prefix=NONTRAPPING-FPTOINT
+// RUN: %clang --target=wasm32-unknown-unknown -### %s -mno-nontrapping-fptoint 2>&1 | FileCheck %s -check-prefix=NO-NONTRAPPING-FPTOINT
+
+// NONTRAPPING-FPTOINT: "-target-feature" "+nontrapping-fptoint"
+// NO-NONTRAPPING-FPTOINT: "-target-feature" "-nontrapping-fptoint"
+// DEFAULT-NOT: "-target-feature" "-nontrapping-fptoint"
+// MVP-NOT: "-target-feature" "+nontrapping-fptoint"
+// BLEEDING-EDGE-NOT: "-target-feature" "-nontrapping-fptoint"