3 files changed, 34 insertions, 22 deletions

diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index c50c6476ec5..436076f33b9 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -1697,9 +1697,6 @@ MCSection *TargetLoweringObjectFileWasm::getExplicitSectionGlobal(
       getContext().getWasmSection(Name, Kind, Group,
                                   MCContext::GenericSectionID);
 
-  if (TM.Options.ThreadModel != ThreadModel::Single)
-    Section->setPassive();
-
   return Section;
 }
 
@@ -1730,11 +1727,7 @@ static MCSectionWasm *selectWasmSectionForGlobal(
     (*NextUniqueID)++;
   }
 
-  MCSectionWasm* Section = Ctx.getWasmSection(Name, Kind, Group, UniqueID);
-  if (Section->isWasmData() && TM.Options.ThreadModel != ThreadModel::Single)
-    Section->setPassive();
-
-  return Section;
+  return Ctx.getWasmSection(Name, Kind, Group, UniqueID);
 }
 
 MCSection *TargetLoweringObjectFileWasm::SelectSectionForGlobal(
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
index 8e8b4878c52..768ab7a099c 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
@@ -115,6 +115,10 @@ WebAssemblyTargetMachine::WebAssemblyTargetMachine(
 
   initAsmInfo();
 
+  // Create a subtarget using the unmodified target machine features to
+  // initialize the used feature set with explicitly enabled features.
+  getSubtargetImpl(getTargetCPU(), getTargetFeatureString());
+
   // Note that we don't use setRequiresStructuredCFG(true). It disables
   // optimizations than we're ok with, and want, such as critical edge
   // splitting and tail merging.
@@ -123,6 +127,17 @@ WebAssemblyTargetMachine::WebAssemblyTargetMachine(
 WebAssemblyTargetMachine::~WebAssemblyTargetMachine() = default; // anchor.
 
 const WebAssemblySubtarget *
+WebAssemblyTargetMachine::getSubtargetImpl(std::string CPU,
+                                           std::string FS) const {
+  auto &I = SubtargetMap[CPU + FS];
+  if (!I) {
+    I = llvm::make_unique<WebAssemblySubtarget>(TargetTriple, CPU, FS, *this);
+    UsedFeatures |= I->getFeatureBits();
+  }
+  return I.get();
+}
+
+const WebAssemblySubtarget *
 WebAssemblyTargetMachine::getSubtargetImpl(const Function &F) const {
   Attribute CPUAttr = F.getFnAttribute("target-cpu");
   Attribute FSAttr = F.getFnAttribute("target-features");
@@ -134,15 +149,12 @@ WebAssemblyTargetMachine::getSubtargetImpl(const Function &F) const {
                        ? FSAttr.getValueAsString().str()
                        : TargetFS;
 
-  auto &I = SubtargetMap[CPU + FS];
-  if (!I) {
-    // This needs to be done before we create a new subtarget since any
-    // creation will depend on the TM and the code generation flags on the
-    // function that reside in TargetOptions.
-    resetTargetOptions(F);
-    I = llvm::make_unique<WebAssemblySubtarget>(TargetTriple, CPU, FS, *this);
-  }
-  return I.get();
+  // This needs to be done before we create a new subtarget since any
+  // creation will depend on the TM and the code generation flags on the
+  // function that reside in TargetOptions.
+  resetTargetOptions(F);
+
+  return getSubtargetImpl(CPU, FS);
 }
 
 namespace {
@@ -202,14 +214,15 @@ FunctionPass *WebAssemblyPassConfig::createTargetRegisterAllocator(bool) {
 //===----------------------------------------------------------------------===//
 
 void WebAssemblyPassConfig::addIRPasses() {
-  if (TM->Options.ThreadModel == ThreadModel::Single) {
-    // In "single" mode, atomics get lowered to non-atomics.
-    addPass(createLowerAtomicPass());
-    addPass(new StripThreadLocal());
-  } else {
+  if (static_cast<WebAssemblyTargetMachine *>(TM)
+          ->getUsedFeatures()[WebAssembly::FeatureAtomics]) {
     // Expand some atomic operations. WebAssemblyTargetLowering has hooks which
     // control specifically what gets lowered.
     addPass(createAtomicExpandPass());
+  } else {
+    // If atomics are not enabled, they get lowered to non-atomics.
+    addPass(createLowerAtomicPass());
+    addPass(new StripThreadLocal());
   }
 
   // Add signatures to prototype-less function declarations
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.h b/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.h
index e13ad7d4eac..0630797fe81 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.h
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.h
@@ -23,6 +23,7 @@ namespace llvm {
 class WebAssemblyTargetMachine final : public LLVMTargetMachine {
   std::unique_ptr<TargetLoweringObjectFile> TLOF;
   mutable StringMap<std::unique_ptr<WebAssemblySubtarget>> SubtargetMap;
+  mutable FeatureBitset UsedFeatures;
 
 public:
   WebAssemblyTargetMachine(const Target &T, const Triple &TT, StringRef CPU,
@@ -32,6 +33,9 @@ public:
                            bool JIT);
 
   ~WebAssemblyTargetMachine() override;
+
+  const WebAssemblySubtarget *getSubtargetImpl(std::string CPU,
+                                               std::string FS) const;
   const WebAssemblySubtarget *
   getSubtargetImpl(const Function &F) const override;
 
@@ -42,6 +46,8 @@ public:
     return TLOF.get();
   }
 
+  FeatureBitset getUsedFeatures() const { return UsedFeatures; }
+
   TargetTransformInfo getTargetTransformInfo(const Function &F) override;
 
   bool usesPhysRegsForPEI() const override { return false; }