[clang] [OpenACC] Implement 'if' clause for Compute Constructs (PR #88411)

[via cfe-commits]

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@@ -11099,6 +11099,19 @@ OpenACCClause *TreeTransform<Derived>::TransformOpenACCClause(
     ParsedClause.setDefaultDetails(
         cast<OpenACCDefaultClause>(OldClause)->getDefaultClauseKind());
     break;
+  case OpenACCClauseKind::If: {
+    Expr *Cond = const_cast<Expr *>(
+        cast<OpenACCIfClause>(OldClause)->getConditionExpr());
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cor3ntin wrote:

Can we add an assert that Cond is not null?
(I guess the logic here is that if the if clause is invalid, it will never be transformed?)

https://github.com/llvm/llvm-project/pull/88411