[flang][runtime] Signal new I/O error on floating-point input overflow

Besides raising the IEEE floating-point overflow exception, treat
a floating-point overflow on input as an I/O error catchable with
ERR=, IOSTAT=, &/or IOMSG=.

Differential Revision: https://reviews.llvm.org/D127022

flang/include/flang/Runtime/iostat.h

@@ -74,6 +74,7 @@ enum Iostat {
   IostatBadWaitUnit,
   IostatBOZInputOverflow,
   IostatIntegerInputOverflow,
+  IostatRealInputOverflow,
 };
 
 const char *IostatErrorString(int);

flang/runtime/edit-input.cpp

@@ -428,6 +428,9 @@ static bool TryFastPathRealInput(
   io.HandleRelativePosition(p - str);
   // Set FP exception flags
   if (converted.flags != decimal::ConversionResultFlags::Exact) {
+    if (converted.flags & decimal::ConversionResultFlags::Overflow) {
+      return false; // let slow path deal with it
+    }
     RaiseFPExceptions(converted.flags);
   }
   return true;
@@ -505,6 +508,10 @@ bool EditCommonRealInput(IoStatementState &io, const DataEdit &edit, void *n) {
       converted.binary;
   // Set FP exception flags
   if (converted.flags != decimal::ConversionResultFlags::Exact) {
+    if (converted.flags & decimal::ConversionResultFlags::Overflow) {
+      io.GetIoErrorHandler().SignalError(IostatRealInputOverflow);
+      return false;
+    }
     RaiseFPExceptions(converted.flags);
   }
   return true;

flang/runtime/iostat.cpp

@@ -92,6 +92,8 @@ const char *IostatErrorString(int iostat) {
     return "B/O/Z input value overflows variable";
   case IostatIntegerInputOverflow:
     return "Integer input value overflows variable";
+  case IostatRealInputOverflow:
+    return "Real or complex input value overflows type";
   default:
     return nullptr;
   }