[clang][FPEnv] Diagnose Strict FP pragmas if target does not support StrictFP

Reviewers: sepavloff, kpn, aaron.ballman

Differential Revision: https://reviews.llvm.org/D90316

Author: Melanie Blower

clang/include/clang/Basic/DiagnosticParseKinds.td

@@ -1147,6 +1147,9 @@ def warn_stdc_fenv_round_not_supported :
 def warn_stdc_unknown_rounding_mode : Warning<
   "invalid or unsupported rounding mode in '#pragma STDC FENV_ROUND' - ignored">,
   InGroup<IgnoredPragmas>;
+def warn_pragma_fp_ignored : Warning<
+  "'#pragma %0' is not supported on this target - ignored">,
+  InGroup<IgnoredPragmas>;
 // - #pragma comment
 def err_pragma_comment_malformed : Error<
   "pragma comment requires parenthesized identifier and optional string">;

clang/lib/Parse/ParsePragma.cpp

@@ -103,6 +103,12 @@ struct PragmaSTDC_FENV_ACCESSHandler : public PragmaHandler {
 
   void HandlePragma(Preprocessor &PP, PragmaIntroducer Introducer,
                     Token &Tok) override {
+    Token PragmaName = Tok;
+    if (!PP.getTargetInfo().hasStrictFP() && !PP.getLangOpts().ExpStrictFP) {
+      PP.Diag(Tok.getLocation(), diag::warn_pragma_fp_ignored)
+          << PragmaName.getIdentifierInfo()->getName();
+      return;
+    }
     tok::OnOffSwitch OOS;
     if (PP.LexOnOffSwitch(OOS))
      return;
@@ -2553,6 +2559,12 @@ void PragmaFloatControlHandler::HandlePragma(Preprocessor &PP,
                                              Token &Tok) {
   Sema::PragmaMsStackAction Action = Sema::PSK_Set;
   SourceLocation FloatControlLoc = Tok.getLocation();
+  Token PragmaName = Tok;
+  if (!PP.getTargetInfo().hasStrictFP() && !PP.getLangOpts().ExpStrictFP) {
+    PP.Diag(Tok.getLocation(), diag::warn_pragma_fp_ignored)
+        << PragmaName.getIdentifierInfo()->getName();
+    return;
+  }
   PP.Lex(Tok);
   if (Tok.isNot(tok::l_paren)) {
     PP.Diag(FloatControlLoc, diag::err_expected) << tok::l_paren;
@@ -2952,6 +2964,11 @@ void PragmaSTDC_FENV_ROUNDHandler::HandlePragma(Preprocessor &PP,
                                                 Token &Tok) {
   Token PragmaName = Tok;
   SmallVector<Token, 1> TokenList;
+  if (!PP.getTargetInfo().hasStrictFP() && !PP.getLangOpts().ExpStrictFP) {
+    PP.Diag(Tok.getLocation(), diag::warn_pragma_fp_ignored)
+        << PragmaName.getIdentifierInfo()->getName();
+    return;
+  }
 
   PP.Lex(Tok);
   if (Tok.isNot(tok::identifier)) {

clang/test/Parser/pragma-fp-warn.c

@@ -0,0 +1,19 @@
+
+// RUN: %clang_cc1 -triple wasm32 -fsyntax-only -Wno-unknown-pragmas -Wignored-pragmas -verify %s
+// RUN: %clang_cc1 -triple thumbv7 -fsyntax-only -Wno-unknown-pragmas -Wignored-pragmas -verify %s
+// RUN: %clang_cc1 -triple aarch64 -fsyntax-only -Wno-unknown-pragmas -Wignored-pragmas -verify %s
+// RUN: %clang_cc1 -DEXPOK -triple x86_64 -fsyntax-only -Wno-unknown-pragmas -Wignored-pragmas -verify %s
+// RUN: %clang_cc1 -DEXPOK -triple systemz -fsyntax-only -Wno-unknown-pragmas -Wignored-pragmas -verify %s
+// RUN: %clang_cc1 -DEXPOK -triple powerpc -fsyntax-only -Wno-unknown-pragmas -Wignored-pragmas -verify %s
+#ifdef EXPOK
+// expected-no-diagnostics
+#else
+// expected-warning@+4 {{'#pragma float_control' is not supported on this target - ignored}}
+// expected-warning@+5 {{'#pragma FENV_ACCESS' is not supported on this target - ignored}}
+// expected-warning@+6 {{'#pragma FENV_ROUND' is not supported on this target - ignored}}
+#endif
+#pragma float_control(precise, on)
+
+#pragma STDC FENV_ACCESS OFF
+
+#pragma STDC FENV_ROUND FE_DOWNWARD