[clang] [HLSL] Default and Relaxed Availability Diagnostics (PR #92704)

[Chris B via cfe-commits]

================
@@ -290,3 +294,295 @@ void SemaHLSL::DiagnoseAttrStageMismatch(
       << A << HLSLShaderAttr::ConvertShaderTypeToStr(Stage)
       << (AllowedStages.size() != 1) << join(StageStrings, ", ");
 }
+
+namespace {
+
+/// This class implements HLSL availability diagnostics for default
+/// and relaxed mode
+///
+/// The goal of this diagnostic is to emit an error or warning when an
+/// unavailable API is found in a code that is reachable from the shader
+/// entry function or from an exported function (when compiling shader
+/// library).
+///
+/// This is done by traversing the AST of all shader entry point functions
+/// and of all exported functions, and any functions that are refrenced
+/// from this AST. In other words, any function that are reachable from
+/// the entry points.
+class DiagnoseHLSLAvailability
+    : public RecursiveASTVisitor<DiagnoseHLSLAvailability> {
+  // HEKOTAS this is probably not needed
+  // typedef RecursiveASTVisitor<DiagnoseHLSLAvailability> Base;
+
+  Sema &SemaRef;
+
+  // Stack of functions to be scaned
+  llvm::SmallVector<const FunctionDecl *, 8> DeclsToScan;
+
+  // List of functions that were already scanned and in which environment.
+  //
+  // Maps FunctionDecl to a unsigned number that represents a set of shader
+  // environments the function has been scanned for.
+  // Since HLSLShaderAttr::ShaderType enum is generated from Attr.td and is
+  // defined without any assigned values, it is guaranteed to be numbered
+  // sequentially from 0 up and we can use it to 'index' individual bits
+  // in the set.
+  // The N'th bit in the set will be set if the function has been scanned
+  // in shader environment whose ShaderType integer value equals N.
+  // For example, if a function has been scanned in compute and pixel stage
+  // environment, the value will be 0x21 (100001 binary) because
+  // (int)HLSLShaderAttr::ShaderType::Pixel == 1 and
+  // (int)HLSLShaderAttr::ShaderType::Compute == 5.
+  llvm::DenseMap<const FunctionDecl *, unsigned> ScannedDecls;
+
+  // Do not access these directly, use the get/set methods below to make
+  // sure the values are in sync
+  llvm::Triple::EnvironmentType CurrentShaderEnvironment;
+  unsigned CurrentShaderStageBit;
+
+  // True if scanning a function that was already scanned in a different
+  // shader stage context, and therefore we should not report issues that
+  // depend only on shader model version because they would be duplicate.
+  bool ReportOnlyShaderStageIssues;
+
+  void SetShaderStageContext(HLSLShaderAttr::ShaderType ShaderType) {
+    assert((((unsigned)1) << (unsigned)ShaderType) != 0 &&
+           "ShaderType is too big for this bitmap");
+    CurrentShaderEnvironment = HLSLShaderAttr::getTypeAsEnvironment(ShaderType);
+    CurrentShaderStageBit = (1 << ShaderType);
+  }
+  void SetUnknownShaderStageContext() {
+    CurrentShaderEnvironment =
+        llvm::Triple::EnvironmentType::UnknownEnvironment;
+    CurrentShaderStageBit = (1 << 31);
+  }
+  llvm::Triple::EnvironmentType GetCurrentShaderEnvironment() {
+    return CurrentShaderEnvironment;
+  }
+  bool InUnknownShaderStageContext() {
+    return CurrentShaderEnvironment ==
+           llvm::Triple::EnvironmentType::UnknownEnvironment;
+  }
+
+  // Scanning methods
+  void HandleFunctionOrMethodRef(FunctionDecl *FD, Expr *RefExpr);
+  void CheckDeclAvailability(NamedDecl *D, const AvailabilityAttr *AA,
+                             SourceRange Range);
+  const AvailabilityAttr *FindAvailabilityAttr(const Decl *D);
+  bool HasMatchingEnvironmentOrNone(const AvailabilityAttr *AA);
+  bool WasAlreadyScannedInCurrentShaderStage(const FunctionDecl *FD,
+                                             bool *WasNeverScanned = nullptr);
+  void AddToScannedFunctions(const FunctionDecl *FD);
+
+public:
+  DiagnoseHLSLAvailability(Sema &SemaRef) : SemaRef(SemaRef) {}
+
+  // AST traversal methods
+  void RunOnTranslationUnit(const TranslationUnitDecl *TU);
+  void RunOnFunction(const FunctionDecl *FD);
+
+  bool VisitDeclRefExpr(DeclRefExpr *DRE) {
+    FunctionDecl *FD = llvm::dyn_cast<FunctionDecl>(DRE->getDecl());
+    if (FD)
+      HandleFunctionOrMethodRef(FD, DRE);
+    return true;
+  }
+
+  bool VisitMemberExpr(MemberExpr *ME) {
+    FunctionDecl *FD = llvm::dyn_cast<FunctionDecl>(ME->getMemberDecl());
+    if (FD)
+      HandleFunctionOrMethodRef(FD, ME);
+    return true;
+  }
+};
+
+// Returns true if the function has already been scanned in the current
+// shader environment. WasNeverScanned will be set to true if the function
+// has never been scanned before for any shader environment.
+bool DiagnoseHLSLAvailability::WasAlreadyScannedInCurrentShaderStage(
+    const FunctionDecl *FD, bool *WasNeverScanned) {
+  const unsigned &ScannedStages = ScannedDecls.getOrInsertDefault(FD);
+  if (WasNeverScanned)
+    *WasNeverScanned = (ScannedStages == 0);
+  return ScannedStages & CurrentShaderStageBit;
+}
+
+// Marks the function as scanned in the current shader environment
+void DiagnoseHLSLAvailability::AddToScannedFunctions(const FunctionDecl *FD) {
+  unsigned &ScannedStages = ScannedDecls.getOrInsertDefault(FD);
+  ScannedStages |= CurrentShaderStageBit;
+}
+
+void DiagnoseHLSLAvailability::HandleFunctionOrMethodRef(FunctionDecl *FD,
+                                                         Expr *RefExpr) {
+  assert((isa<DeclRefExpr>(RefExpr) || isa<MemberExpr>(RefExpr)) &&
+         "expected DeclRefExpr or MemberExpr");
+
+  // has a definition -> add to stack to be scanned
+  const FunctionDecl *FDWithBody = nullptr;
+  if (FD->hasBody(FDWithBody)) {
+    if (!WasAlreadyScannedInCurrentShaderStage(FDWithBody))
+      DeclsToScan.push_back(FDWithBody);
+    return;
+  }
+
+  // no body -> diagnose availability
+  const AvailabilityAttr *AA = FindAvailabilityAttr(FD);
+  if (AA)
+    CheckDeclAvailability(
+        FD, AA, SourceRange(RefExpr->getBeginLoc(), RefExpr->getEndLoc()));
+}
+
+void DiagnoseHLSLAvailability::RunOnTranslationUnit(
+    const TranslationUnitDecl *TU) {
+  // Iterate over all shader entry functions and library exports, and for those
+  // that have a body (definiton), run diag scan on each, setting appropriate
+  // shader environment context based on whether it is a shader entry function
+  // or an exported function.
+  for (auto &D : TU->decls()) {
+    const FunctionDecl *FD = llvm::dyn_cast<FunctionDecl>(D);
+    if (!FD || !FD->isThisDeclarationADefinition())
+      continue;
+
+    // shader entry point
+    auto ShaderAttr = FD->getAttr<HLSLShaderAttr>();
+    if (ShaderAttr) {
+      SetShaderStageContext(ShaderAttr->getType());
+      RunOnFunction(FD);
+      continue;
+    }
+    // exported library function with definition
+    // FIXME: tracking issue #92073
+#if 0
+    if (FD->getFormalLinkage() == Linkage::External) {
+      SetUnknownShaderStageContext();
+      RunOnFunction(FD);
+    }
+#endif
+  }
+}
+
+void DiagnoseHLSLAvailability::RunOnFunction(const FunctionDecl *FD) {
+  assert(DeclsToScan.empty() && "DeclsToScan should be empty");
+  DeclsToScan.push_back(FD);
+
+  while (!DeclsToScan.empty()) {
+    // Take one decl from the stack and check it by traversing its AST.
+    // For any CallExpr found during the traversal add it's callee to the top of
+    // the stack to be processed next. Functions already processed are stored in
+    // ScannedDecls.
+    const FunctionDecl *FD = DeclsToScan.back();
+    DeclsToScan.pop_back();
+
+    // Decl was already scanned
+    bool WasNeverScanned;
+    if (WasAlreadyScannedInCurrentShaderStage(FD, &WasNeverScanned))
+      continue;
+
+    ReportOnlyShaderStageIssues = !WasNeverScanned;
+
+    AddToScannedFunctions(FD);
+
+    Stmt *Body = FD->getBody();
+    assert(Body && "full definition with body expected here");
----------------
llvm-beanz wrote:

nit: This assert probably doesn't need to be here since you do explicitly check that the decl has a body before adding it to DeclsToScan.

https://github.com/llvm/llvm-project/pull/92704