[clang] [OpenACC] Implement 'cache' construct parsing (PR #74324)

[via cfe-commits]

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@@ -268,6 +270,71 @@ ExprResult Parser::ParseOpenACCRoutineName() {
   return getActions().CorrectDelayedTyposInExpr(Res);
 }
 
+void Parser::ParseOpenACCCacheVar() {
+  ExprResult ArrayName = ParseOpenACCIDExpression();
+  // FIXME: Pass this to Sema.
+  (void)ArrayName;
+
+  // If the expression is invalid, just continue parsing the brackets, there
+  // is likely other useful diagnostics we can emit inside of those.
+
+  BalancedDelimiterTracker SquareBrackets(*this, tok::l_square,
+                                          tok::annot_pragma_openacc_end);
+
+  // Square brackets are required, so error here, and try to recover by moving
+  // until the next comma, or the close paren/end of pragma.
+  if (SquareBrackets.expectAndConsume()) {
+    SkipUntil(tok::comma, tok::r_paren, tok::annot_pragma_openacc_end,
+              Parser::StopBeforeMatch);
+    return;
+  }
+
+  ExprResult Lower = getActions().CorrectDelayedTyposInExpr(ParseExpression());
+  // FIXME: Pass this to Sema.
+  (void)Lower;
+
+  // The 'length' expression is optional, as this could be a single array
+  // element. If there is no colon, we can treat it as that.
+  if (getCurToken().is(tok::colon)) {
+    ConsumeToken();
+    ExprResult Length =
+        getActions().CorrectDelayedTyposInExpr(ParseExpression());
+    // FIXME: Pass this to Sema.
+    (void)Length;
+  }
+
+  // Diagnose the square bracket being in the wrong place and continue.
+  SquareBrackets.consumeClose();
+}
+
+void Parser::ParseOpenACCCacheVarList() {
+  // If this is the end of the line, just return 'false' and count on the close
+  // paren diagnostic to catch the issue.
+  if (getCurToken().isAnnotation())
+    return;
+
+  // The VarList is an optional `readonly:` followed by a list of a variable
+  // specifications.  First, see if we have `readonly:`, else we back-out and
+  // treat it like the beginning of a reference to a potentially-existing
+  // `readonly` variable.
+  if (getPreprocessor().getSpelling(getCurToken()) == "readonly" &&
+      NextToken().is(tok::colon)) {
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cor3ntin wrote:

`getSpelling` is pretty low level and may end up relexing a bunch of things in the presence of line splicing and so forth. So I would really prefer we use getIdentifierInfo (after we check the token is an identifier) 

https://github.com/llvm/llvm-project/pull/74324