[llvm] [DirectX] Infrastructure to collect shader flags for each function (PR #112967)

[S. Bharadwaj Yadavalli via llvm-commits]

================
@@ -13,36 +13,88 @@
 
 #include "DXILShaderFlags.h"
 #include "DirectX.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/IR/DiagnosticInfo.h"
+#include "llvm/IR/DiagnosticPrinter.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Support/FormatVariadic.h"
+#include "llvm/Support/raw_ostream.h"
 
 using namespace llvm;
 using namespace llvm::dxil;
 
-static void updateFlags(ComputedShaderFlags &Flags, const Instruction &I) {
+namespace {
+/// A simple Wrapper DiagnosticInfo that generates Module-level diagnostic
+/// for ShaderFlagsAnalysis pass
+class DiagnosticInfoShaderFlags : public DiagnosticInfo {
+private:
+  const Twine &Msg;
+  const Module &Mod;
+
+public:
+  /// \p M is the module for which the diagnostic is being emitted. \p Msg is
+  /// the message to show. Note that this class does not copy this message, so
+  /// this reference must be valid for the whole life time of the diagnostic.
+  DiagnosticInfoShaderFlags(const Module &M, const Twine &Msg,
+                            DiagnosticSeverity Severity = DS_Error)
+      : DiagnosticInfo(DK_Unsupported, Severity), Msg(Msg), Mod(M) {}
+
+  void print(DiagnosticPrinter &DP) const override {
+    DP << Mod.getName() << ": " << Msg << '\n';
+  }
+};
+} // namespace
+
+static void updateFlags(ComputedShaderFlags &CSF, const Instruction &I) {
   Type *Ty = I.getType();
-  if (Ty->isDoubleTy()) {
-    Flags.Doubles = true;
+  bool DoubleTyInUse = Ty->isDoubleTy();
+  for (Value *Op : I.operands()) {
+    DoubleTyInUse |= Op->getType()->isDoubleTy();
+  }
+
+  if (DoubleTyInUse) {
+    CSF.Doubles = true;
     switch (I.getOpcode()) {
     case Instruction::FDiv:
     case Instruction::UIToFP:
     case Instruction::SIToFP:
     case Instruction::FPToUI:
     case Instruction::FPToSI:
-      Flags.DX11_1_DoubleExtensions = true;
+      // TODO: To be set if I is a call to DXIL intrinsic DXIL::Opcode::Fma
+      CSF.DX11_1_DoubleExtensions = true;
       break;
     }
   }
 }
 
-ComputedShaderFlags ComputedShaderFlags::computeFlags(Module &M) {
-  ComputedShaderFlags Flags;
-  for (const auto &F : M)
+static bool compareFuncSFPairs(const FuncShaderFlagsMask &First,
+                               const FuncShaderFlagsMask &Second) {
+  return (First.first->getName().compare(Second.first->getName()) < 0);
+}
+
+static DXILModuleShaderFlagsInfo computeFlags(Module &M) {
+  DXILModuleShaderFlagsInfo MSFI;
+  for (auto &F : M) {
+    if (F.isDeclaration())
+      continue;
+    // Each of the functions in a module are unique. Hence no prior shader flags
+    // mask of the function should be present.
+    if (MSFI.hasShaderFlagsMask(&F)) {
----------------
bharadwajy wrote:

> `hasShaderFlagsMask` does a binary search through `FuncShaderFlagsVec`. However, `FuncShaderFlagsVec` is not necessarily sorted, because new entries are added inside the loop and it is only sorted after the loop exits.
> 
> This is probably moot since the functions in the module are meant to be unique, which then makes me wonder why this check is here at all.

Yes. That is a mistake and a bug. Fixed by creating a pre-sorted function list of the module that is used to collect shader flags mask.

https://github.com/llvm/llvm-project/pull/112967