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

[Chris B via llvm-commits]

================
@@ -61,6 +66,21 @@ void ModuleShaderFlags::initialize(const Module &M) {
     CombinedSFMask.merge(CSF);
   }
   llvm::sort(FunctionFlags);
+  // Propagate shader flag mask of functions to their callers.
+  while (!WorkList.empty()) {
+    const Function *Func = WorkList.pop_back_val();
+    if (!Func->user_empty()) {
+      const ComputedShaderFlags &FuncSF = getFunctionFlags(Func);
+      // Update mask of callers with that of Func
+      for (const auto User : Func->users()) {
+        if (const CallInst *CI = dyn_cast<CallInst>(User)) {
+          const Function *Caller = CI->getParent()->getParent();
+          if (mergeFunctionShaderFlags(Caller, FuncSF))
+            WorkList.push_back(Caller);
+        }
+      }
+    }
----------------
llvm-beanz wrote:

A few different style nits here:
```suggestion
    if (Func->user_empty())
      continue;
    const ComputedShaderFlags &FuncSF = getFunctionFlags(Func);
    // Update mask of callers with that of Func
    for (const auto *User : Func->users()) {
      const CallInst *CI = dyn_cast<CallInst>(User);
      if (!CI)
        continue;
      const Function *Caller = CI->getParent()->getParent();
      if (mergeFunctionShaderFlags(Caller, FuncSF))
        WorkList.push_back(Caller);
    }
```
see:
* [Prefer continue](https://llvm.org/docs/CodingStandards.html#use-early-exits-and-continue-to-simplify-code)
* [Omit braces for single statements](https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements)
* [Explicitly specify `*` or `&` with `auto`](https://llvm.org/docs/CodingStandards.html#beware-unnecessary-copies-with-auto)

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