Revert "[compiler-rt][nsan] Add support for nan detection" (#105909)

Reverts #101531

Fails https://lab.llvm.org/buildbot/#/builders/66/builds/3051

compiler-rt/lib/nsan/nsan.cpp

@@ -445,32 +445,6 @@ int32_t checkFT(const FT value, ShadowFT Shadow, CheckTypeT CheckType,
   const InternalFT check_value = value;
   const InternalFT check_shadow = Shadow;
 
-  // We only check for NaNs in the value, not the shadow.
-  if (flags().check_nan && isnan(check_value)) {
-    GET_CALLER_PC_BP;
-    BufferedStackTrace stack;
-    stack.Unwind(pc, bp, nullptr, false);
-    if (GetSuppressionForStack(&stack, CheckKind::Consistency)) {
-      // FIXME: optionally print.
-      return flags().resume_after_suppression ? kResumeFromValue
-                                              : kContinueWithShadow;
-    }
-    Decorator D;
-    Printf("%s", D.Warning());
-    Printf("WARNING: NumericalStabilitySanitizer: NaN detected\n");
-    Printf("%s", D.Default());
-    stack.Print();
-    if (flags().halt_on_error) {
-      if (common_flags()->abort_on_error)
-        Printf("ABORTING\n");
-      else
-        Printf("Exiting\n");
-      Die();
-    }
-    // Performing other tests for NaN values is meaningless when dealing with numbers.
-    return kResumeFromValue;
-  }
-
   // See this article for an interesting discussion of how to compare floats:
   // https://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/
   static constexpr const FT Eps = FTInfo<FT>::kEpsilon;

compiler-rt/lib/nsan/nsan_flags.inc

@@ -48,5 +48,3 @@ NSAN_FLAG(bool, enable_loadtracking_stats, false,
           "due to invalid or unknown types.")
 NSAN_FLAG(bool, poison_in_free, true, "")
 NSAN_FLAG(bool, print_stats_on_exit, false, "If true, print stats on exit.")
-NSAN_FLAG(bool, check_nan, false,
-          "If true, check the floating-point number is nan")