[clang] [CIR] Add inline function attributes (PR #162866)

[Andy Kaylor via cfe-commits]

================
@@ -1885,6 +1885,87 @@ void CIRGenModule::setFunctionAttributes(GlobalDecl globalDecl,
   }
 }
 
+void CIRGenModule::setCIRFunctionAttributesForDefinition(
+    const clang::FunctionDecl *decl, cir::FuncOp f) {
+  assert(!cir::MissingFeatures::opFuncUnwindTablesAttr());
+  assert(!cir::MissingFeatures::stackProtector());
+
+  auto existingInlineKind = f.getInlineKind();
+  bool isNoInline =
+      existingInlineKind && *existingInlineKind == cir::InlineKind::NoInline;
+  bool isAlwaysInline = existingInlineKind &&
+                        *existingInlineKind == cir::InlineKind::AlwaysInline;
+
+  if (!decl) {
+    assert(!cir::MissingFeatures::hlsl());
+
+    if (!isAlwaysInline &&
+        codeGenOpts.getInlining() == CodeGenOptions::OnlyAlwaysInlining) {
+      // If we don't have a declaration to control inlining, the function isn't
+      // explicitly marked as alwaysinline for semantic reasons, and inlining is
+      // disabled, mark the function as noinline.
----------------
andykaylor wrote:

```suggestion
      // If inlining is disabled and we don't have a declaration to control
      // inlining, mark the function as 'noinline' unless it is explicitly marked
      // as 'alwaysinline'.
```
I found the original comment confusing. Do you think this is better? It doesn't match the order in which the code checks things, but I think it corresponds better to the actual logic of the situation.

https://github.com/llvm/llvm-project/pull/162866