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

[Mike Rice via cfe-commits]

================
@@ -290,3 +294,296 @@ 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 code that is reachable from the shader
+/// entry function or from an exported function (when compiling a 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 functions that are reachable from
+/// the entry points.
+class DiagnoseHLSLAvailability
+    : public RecursiveASTVisitor<DiagnoseHLSLAvailability> {
+
+  Sema &SemaRef;
+
+  // Stack of functions to be scaned
+  llvm::SmallVector<const FunctionDecl *, 8> DeclsToScan;
+
+  // Tracks which environments functions have been scanned in.
+  //
+  // Maps FunctionDecl to an unsigned number that represents the 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.
+  // A FunctionDecl is mapped to 0 (or not included in the map) if it has not
+  // been scanned in any environment.
+  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;
----------------
mikerice1969 wrote:

Hi @hekota, just following up on some static verifier hits. These three members are reported as not initialized in the constructor. Is it possible to initialize these to a sane default? That would make it clear to random readers (and static verifier tools) that it wasn't overlooked.

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