[clang] [clang] Factor out OpenACC part of `Sema` (PR #84184)

[Erich Keane via cfe-commits]

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@@ -1162,6 +1162,11 @@ class Sema final {
   /// CurContext - This is the current declaration context of parsing.
   DeclContext *CurContext;
 
+  SemaOpenACC &OpenACC() {
+    assert(OpenACCPtr);
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erichkeane wrote:

I don't buy the 'noticeable impact on assertion build' here.  The very next line is loading the same variable, so even the smallest amount of inliner action makes this at best a non-taken 'jne' type instruction.  

While this MIGHT have a slight impact, it is near-zero, and of the order of 'i used a pair of if/else instead of a switch'.

https://github.com/llvm/llvm-project/pull/84184