[WebAssembly] Add mutable globals feature

[tlively]

Summary

This feature is not actually used for anything in the WebAssembly
backend, but adding it allows users to get it into the target features
sections of their objects, which makes these objects
future-compatible.

clang/include/clang/Driver/Options.td

 def msign_ext : Flag<["-"], "msign-ext">, Group<m_wasm_Features_Group>;
 def mno_sign_ext : Flag<["-"], "mno-sign-ext">, Group<m_wasm_Features_Group>;
 def mexception_handing : Flag<["-"], "mexception-handling">, Group<m_wasm_Features_Group>;
 def mno_exception_handing : Flag<["-"], "mno-exception-handling">, Group<m_wasm_Features_Group>;
 def matomics : Flag<["-"], "matomics">, Group<m_wasm_Features_Group>;
 def mno_atomics : Flag<["-"], "mno-atomics">, Group<m_wasm_Features_Group>;
 def mbulk_memory : Flag<["-"], "mbulk-memory">, Group<m_wasm_Features_Group>;
 def mno_bulk_memory : Flag<["-"], "mno-bulk-memory">, Group<m_wasm_Features_Group>;
+def mmutable_globals : Flag<["-"], "mmutable-globals">, Group<m_wasm_Features_Group>;
+def mno_mutable_globals : Flag<["-"], "mno-mutable-globals">, Group<m_wasm_Features_Group>;
 
 def mamdgpu_debugger_abi : Joined<["-"], "mamdgpu-debugger-abi=">,
   Flags<[HelpHidden]>,
   Group<m_Group>,
   HelpText<"Generate additional code for specified <version> of debugger ABI (AMDGPU only)">,
   MetaVarName<"<version>">;
 
 def mcode_object_v3 : Flag<["-"], "mcode-object-v3">, Group<m_amdgpu_Features_Group>,

clang/lib/Basic/Targets/WebAssembly.h

enum SIMDEnum {
     UnimplementedSIMD128,
   } SIMDLevel = NoSIMD;
 
   bool HasNontrappingFPToInt = false;
   bool HasSignExt = false;
   bool HasExceptionHandling = false;
   bool HasBulkMemory = false;
   bool HasAtomics = false;
+  bool HasMutableGlobals = false;
 
 public:
   explicit WebAssemblyTargetInfo(const llvm::Triple &T, const TargetOptions &)
       : TargetInfo(T) {
     NoAsmVariants = true;
     SuitableAlign = 128;
     LargeArrayMinWidth = 128;
     LargeArrayAlign = 128;

clang/lib/Basic/Targets/WebAssembly.cpp

bool WebAssemblyTargetInfo::hasFeature(StringRef Feature) const {
   return llvm::StringSwitch<bool>(Feature)
       .Case("simd128", SIMDLevel >= SIMD128)
       .Case("unimplemented-simd128", SIMDLevel >= UnimplementedSIMD128)
       .Case("nontrapping-fptoint", HasNontrappingFPToInt)
       .Case("sign-ext", HasSignExt)
       .Case("exception-handling", HasExceptionHandling)
       .Case("bulk-memory", HasBulkMemory)
       .Case("atomics", HasAtomics)
+      .Case("mutable-globals", HasMutableGlobals)
       .Default(false);
 }
 
 bool WebAssemblyTargetInfo::isValidCPUName(StringRef Name) const {
   return llvm::find(ValidCPUNames, Name) != std::end(ValidCPUNames);
 }
 
 void WebAssemblyTargetInfo::fillValidCPUList(
void WebAssemblyTargetInfo::getTargetDefines(const LangOptions &Opts,
   if (HasSignExt)
     Builder.defineMacro("__wasm_sign_ext__");
   if (HasExceptionHandling)
     Builder.defineMacro("__wasm_exception_handling__");
   if (HasBulkMemory)
     Builder.defineMacro("__wasm_bulk_memory__");
   if (HasAtomics)
     Builder.defineMacro("__wasm_atomics__");
+  if (HasMutableGlobals)
+    Builder.defineMacro("__wasm_mutable_globals__");
 }
 
 void WebAssemblyTargetInfo::setSIMDLevel(llvm::StringMap<bool> &Features,
                                          SIMDEnum Level) {
   switch (Level) {
   case UnimplementedSIMD128:
     Features["unimplemented-simd128"] = true;
     LLVM_FALLTHROUGH;
   case SIMD128:
     Features["simd128"] = true;
     LLVM_FALLTHROUGH;
   case NoSIMD:
     break;
   }
 }
 
 bool WebAssemblyTargetInfo::initFeatureMap(
     llvm::StringMap<bool> &Features, DiagnosticsEngine &Diags, StringRef CPU,
     const std::vector<std::string> &FeaturesVec) const {
   if (CPU == "bleeding-edge") {
     Features["nontrapping-fptoint"] = true;
     Features["sign-ext"] = true;
     Features["atomics"] = true;
+    Features["mutable-globals"] = true;
     setSIMDLevel(Features, SIMD128);
   }
   // Other targets do not consider user-configured features here, but while we
   // are actively developing new features it is useful to let user-configured
   // features control availability of builtins
   setSIMDLevel(Features, SIMDLevel);
   if (HasNontrappingFPToInt)
     Features["nontrapping-fptoint"] = true;
   if (HasSignExt)
     Features["sign-ext"] = true;
   if (HasExceptionHandling)
     Features["exception-handling"] = true;
   if (HasBulkMemory)
     Features["bulk-memory"] = true;
   if (HasAtomics)
     Features["atomics"] = true;
+  if (HasMutableGlobals)
+    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) {
     if (Feature == "+simd128") {
for (const auto &Feature : Features) {
     if (Feature == "+atomics") {
       HasAtomics = true;
       continue;
     }
     if (Feature == "-atomics") {
       HasAtomics = false;
       continue;
     }
+    if (Feature == "+mutable-globals") {
+      HasMutableGlobals = true;
+      continue;
+    }
+    if (Feature == "-mutable-globals") {
+      HasMutableGlobals = false;
+      continue;
+    }
 
     Diags.Report(diag::err_opt_not_valid_with_opt)
         << Feature << "-target-feature";
     return false;
   }
   return true;
 }
 

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

 // RUN:   | FileCheck %s -check-prefix=PTHREAD
 // RUN: %clang -E -dM %s -o - 2>&1 \
 // RUN:     -target wasm64-unknown-unknown -pthread \
 // RUN:   | FileCheck %s -check-prefix=PTHREAD
 //
 // PTHREAD:#define __wasm_atomics__ 1{{$}}
 
 // RUN: %clang -E -dM %s -o - 2>&1 \
+// RUN:     -target wasm32-unknown-unknown -mmutable-globals \
+// RUN:   | FileCheck %s -check-prefix=MUTABLE-GLOBALS
+// RUN: %clang -E -dM %s -o - 2>&1 \
+// RUN:     -target wasm64-unknown-unknown -mmutable-globals \
+// RUN:   | FileCheck %s -check-prefix=MUTABLE-GLOBALS
+//
+// MUTABLE-GLOBALS:#define __wasm_mutable_globals__ 1{{$}}
+
+// RUN: %clang -E -dM %s -o - 2>&1 \
 // RUN:     -target wasm32-unknown-unknown -mcpu=mvp \
 // RUN:   | FileCheck %s -check-prefix=MVP
 // RUN: %clang -E -dM %s -o - 2>&1 \
 // RUN:     -target wasm64-unknown-unknown -mcpu=mvp \
 // RUN:   | FileCheck %s -check-prefix=MVP
 //
 // MVP-NOT:#define __wasm_simd128__
 // MVP-NOT:#define __wasm_unimplemented_simd128__
 // MVP-NOT:#define __wasm_nontrapping_fptoint__
 // MVP-NOT:#define __wasm_sign_ext__
 // MVP-NOT:#define __wasm_exception_handling__
 // MVP-NOT:#define __wasm_bulk_memory__
 // MVP-NOT:#define __wasm_atomics__
+// MVP-NOT:#define __wasm_mutable_globals__
 
 // RUN: %clang -E -dM %s -o - 2>&1 \
 // RUN:     -target wasm32-unknown-unknown -mcpu=bleeding-edge \
 // RUN:   | FileCheck %s -check-prefix=BLEEDING-EDGE
 // RUN: %clang -E -dM %s -o - 2>&1 \
 // RUN:     -target wasm64-unknown-unknown -mcpu=bleeding-edge \
 // RUN:   | FileCheck %s -check-prefix=BLEEDING-EDGE
 //
 // BLEEDING-EDGE-DAG:#define __wasm_nontrapping_fptoint__ 1{{$}}
 // BLEEDING-EDGE-DAG:#define __wasm_sign_ext__ 1{{$}}
 // BLEEDING-EDGE-DAG:#define __wasm_simd128__ 1{{$}}
 // BLEEDING-EDGE-DAG:#define __wasm_atomics__ 1{{$}}
+// BLEEDING-EDGE-DAG:#define __wasm_mutable_globals__ 1{{$}}
 // BLEEDING-EDGE-NOT:#define __wasm_unimplemented_simd128__ 1{{$}}
 
 // RUN: %clang -E -dM %s -o - 2>&1 \
 // RUN:     -target wasm32-unknown-unknown -mcpu=bleeding-edge -mno-simd128 \
 // RUN:   | FileCheck %s -check-prefix=BLEEDING-EDGE-NO-SIMD128
 // RUN: %clang -E -dM %s -o - 2>&1 \
 // RUN:     -target wasm64-unknown-unknown -mcpu=bleeding-edge -mno-simd128 \
 // RUN:   | FileCheck %s -check-prefix=BLEEDING-EDGE-NO-SIMD128
 //
 // BLEEDING-EDGE-NO-SIMD128-NOT:#define __wasm_simd128__

llvm/lib/Target/WebAssembly/WebAssembly.td

 def FeatureExceptionHandling :
       SubtargetFeature<"exception-handling", "HasExceptionHandling", "true",
                        "Enable Wasm exception handling">;
 
 def FeatureBulkMemory :
       SubtargetFeature<"bulk-memory", "HasBulkMemory", "true",
                        "Enable bulk memory operations">;
 
+def FeatureMutableGlobals :
+      SubtargetFeature<"mutable-globals", "HasMutableGlobals", "true",
+                       "Enable mutable globals">;
+
 //===----------------------------------------------------------------------===//
 // Architectures.
 //===----------------------------------------------------------------------===//
 
 //===----------------------------------------------------------------------===//
 // Register File Description
 //===----------------------------------------------------------------------===//
 

llvm/lib/Target/WebAssembly/WebAssemblySubtarget.h

enum SIMDEnum {
     UnimplementedSIMD128,
   } SIMDLevel = NoSIMD;
 
   bool HasAtomics = false;
   bool HasNontrappingFPToInt = false;
   bool HasSignExt = false;
   bool HasExceptionHandling = false;
   bool HasBulkMemory = false;
+  bool HasMutableGlobals = false;
 
   /// String name of used CPU.
   std::string CPUString;
 
   /// What processor and OS we're targeting.
   Triple TargetTriple;
 
   WebAssemblyFrameLowering FrameLowering;
public:
   bool hasUnimplementedSIMD128() const {
     return SIMDLevel >= UnimplementedSIMD128;
   }
   bool hasAtomics() const { return HasAtomics; }
   bool hasNontrappingFPToInt() const { return HasNontrappingFPToInt; }
   bool hasSignExt() const { return HasSignExt; }
   bool hasExceptionHandling() const { return HasExceptionHandling; }
   bool hasBulkMemory() const { return HasBulkMemory; }
+  bool hasMutableGlobals() const { return HasMutableGlobals; }
 
   /// Parses features string setting specified subtarget options. Definition of
   /// function is auto generated by tblgen.
   void ParseSubtargetFeatures(StringRef CPU, StringRef FS);
 };
 
 } // end namespace llvm
 
 #endif

llvm/test/CodeGen/WebAssembly/mutable-globals.ll

+; RUN: llc < %s -mattr=+mutable-globals | FileCheck %s
+
+; Test that mutable globals is properly emitted into the target features section
+
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
+target triple = "wasm32-unknown-unknown"
+
+define void @foo() {
+  ret void
+}
+
+; CHECK-LABEL: .custom_section.target_features
+; CHECK-NEXT: .int8 1
+; CHECK-NEXT: .int8 43
+; CHECK-NEXT: .int8 15
+; CHECK-NEXT: .ascii "mutable-globals"