[clang] [clang] Macro for constant rounding mode (PR #92699)

[Eli Friedman via cfe-commits]

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@@ -965,6 +965,16 @@ void Preprocessor::Lex(Token &Result) {
   LastTokenWasAt = Result.is(tok::at);
   --LexLevel;
 
+  if (Result.is(tok::l_brace)) {
+    CurlyBraceLevel++;
+  } else if (Result.is(tok::r_brace)) {
+    if (!RoundingPragmas.empty() &&
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efriedma-quic wrote:

Maybe we can move the `!RoundingPragmas.empty()` outside the if statement, so we can skip a little more of the code if the user isn't using any pragmas?  I mean, it probably doesn't make a big difference, but Lex() is performance-sensitive.

https://github.com/llvm/llvm-project/pull/92699