Revert "Currently the control of the eval-method is mixed with fast-math."llvmorg-16.0.0-rc4

Setting __FLT_EVAL_METHOD__ to -1 with fast-math will set
__GLIBC_FLT_EVAL_METHOD to 2 and long double ends up being used for
float_t and double_t. This creates some ABI breakage with various C libraries.
See details here: https://github.com/llvm/llvm-project/issues/60781

This reverts commit bbf0d1932a3c1be970ed8a580e51edf571b80fd5.

(cherry picked from commit 2f1264260b37e9bd79737181e459ae20e10c5fea)

1 files changed, 8 insertions, 29 deletions

diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
index bbc271e5611e..76d0d53ed31d 100644
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -1637,35 +1637,14 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
     Tok.setKind(tok::string_literal);
   } else if (II == Ident__FLT_EVAL_METHOD__) {
     // __FLT_EVAL_METHOD__ is set to the default value.
-    if (getTUFPEvalMethod() ==
-        LangOptions::FPEvalMethodKind::FEM_Indeterminable) {
-      // This is possible if `AllowFPReassoc` or `AllowReciprocal` is enabled.
-      // These modes can be triggered via the command line option `-ffast-math`
-      // or via a `pragam float_control`.
-      // __FLT_EVAL_METHOD__ expands to -1.
-      // The `minus` operator is the next token we read from the stream.
-      auto Toks = std::make_unique<Token[]>(1);
-      OS << "-";
-      Tok.setKind(tok::minus);
-      // Push the token `1` to the stream.
-      Token NumberToken;
-      NumberToken.startToken();
-      NumberToken.setKind(tok::numeric_constant);
-      NumberToken.setLiteralData("1");
-      NumberToken.setLength(1);
-      Toks[0] = NumberToken;
-      EnterTokenStream(std::move(Toks), 1, /*DisableMacroExpansion*/ false,
-                       /*IsReinject*/ false);
-    } else {
-      OS << getTUFPEvalMethod();
-      // __FLT_EVAL_METHOD__ expands to a simple numeric value.
-      Tok.setKind(tok::numeric_constant);
-      if (getLastFPEvalPragmaLocation().isValid()) {
-        // The program is ill-formed. The value of __FLT_EVAL_METHOD__ is
-        // altered by the pragma.
-        Diag(Tok, diag::err_illegal_use_of_flt_eval_macro);
-        Diag(getLastFPEvalPragmaLocation(), diag::note_pragma_entered_here);
-      }
+    OS << getTUFPEvalMethod();
+    // __FLT_EVAL_METHOD__ expands to a simple numeric value.
+    Tok.setKind(tok::numeric_constant);
+    if (getLastFPEvalPragmaLocation().isValid()) {
+      // The program is ill-formed. The value of __FLT_EVAL_METHOD__ is altered
+      // by the pragma.
+      Diag(Tok, diag::err_illegal_use_of_flt_eval_macro);
+      Diag(getLastFPEvalPragmaLocation(), diag::note_pragma_entered_here);
     }
   } else if (II == Ident__COUNTER__) {
     // __COUNTER__ expands to a simple numeric value.