[llvm] [DirectX] Propagate shader flags mask of callees to callers (PR #118306)

[S. Bharadwaj Yadavalli via llvm-commits]

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@@ -84,15 +145,22 @@ void ComputedShaderFlags::print(raw_ostream &OS) const {
 /// Return the shader flags mask of the specified function Func.
 const ComputedShaderFlags &
 ModuleShaderFlags::getFunctionFlags(const Function *Func) const {
-  const auto Iter = llvm::lower_bound(
-      FunctionFlags, Func,
-      [](const std::pair<const Function *, ComputedShaderFlags> FSM,
-         const Function *FindFunc) { return (FSM.first < FindFunc); });
+  auto Iter = FunctionFlags.find(Func);
   assert((Iter != FunctionFlags.end() && Iter->first == Func) &&
-         "No Shader Flags Mask exists for function");
+         "Get Shader Flags : No Shader Flags Mask exists for function");
   return Iter->second;
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bharadwajy wrote:

> This would actually be safer to return `FunctionFlags[Func]` instead of using Find. Then if it fails, the returned result is a default initialized flags structure.

Returning default initialized flags structure value for `F` whose shader flags mask does not exist would amount to providing incorrect information about a function whose existence it has no information about and in addition inserting it to the `DenseMap`. Such functionality is not the intent of `getFunctionFlags()`. Hence the usage of `find` and assertion while getting shader flags for a `Function *F`.

https://github.com/llvm/llvm-project/pull/118306