[flang] Respect BZ mode in exponent parts, too

The Fortran standard discusses BZ mode (treat blanks as zero digits)
explicitly in its effect on the editing of the digits prior to the
exponent part, but doesn't mention it in description of the
exponent part.  Other compilers honor BZ mode in the exponent,
so we should do so too.  So "1 e 1 " is 1.E11 in BZ mode.

Differential Revision: https://reviews.llvm.org/D87653

flang/runtime/edit-input.cpp

@@ -180,10 +180,11 @@ static int ScanRealInput(char *buffer, int bufferSize, IoStatementState &io,
       first == 'E' || first == 'D' || first == 'Q') {
     Put('.'); // input field is normalized to a fraction
     auto start{got};
+    bool bzMode{(edit.modes.editingFlags & blankZero) != 0};
     for (; next; next = io.NextInField(remaining)) {
       char32_t ch{*next};
       if (ch == ' ' || ch == '\t') {
-        if (edit.modes.editingFlags & blankZero) {
+        if (bzMode) {
           ch = '0'; // BZ mode - treat blank as if it were zero
         } else {
           continue;
@@ -206,19 +207,29 @@ static int ScanRealInput(char *buffer, int bufferSize, IoStatementState &io,
     if (next &&
         (*next == 'e' || *next == 'E' || *next == 'd' || *next == 'D' ||
             *next == 'q' || *next == 'Q')) {
+      // Optional exponent letter.  Blanks are allowed between the
+      // optional exponent letter and the exponent value.
       io.SkipSpaces(remaining);
       next = io.NextInField(remaining);
     }
-    exponent = -edit.modes.scale; // default exponent is -kP
+    // The default exponent is -kP, but the scale factor doesn't affect
+    // an explicit exponent.
+    exponent = -edit.modes.scale;
     if (next &&
-        (*next == '-' || *next == '+' || (*next >= '0' && *next <= '9'))) {
+        (*next == '-' || *next == '+' || (*next >= '0' && *next <= '9') ||
+            (bzMode && (*next == ' ' || *next == '\t')))) {
       bool negExpo{*next == '-'};
       if (negExpo || *next == '+') {
         next = io.NextInField(remaining);
       }
-      for (exponent = 0; next && (*next >= '0' && *next <= '9');
-           next = io.NextInField(remaining)) {
-        exponent = 10 * exponent + *next - '0';
+      for (exponent = 0; next; next = io.NextInField(remaining)) {
+        if (*next >= '0' && *next <= '9') {
+          exponent = 10 * exponent + *next - '0';
+        } else if (bzMode && (*next == ' ' || *next == '\t')) {
+          exponent = 10 * exponent;
+        } else {
+          break;
+        }
       }
       if (negExpo) {
         exponent = -exponent;

flang/unittests/Runtime/hello.cpp

@@ -481,6 +481,7 @@ int main() {
   realInTest("(-1P,F18.0)", "               125", 0x4093880000000000); // 1250
   realInTest("(1P,F18.0)", "               125", 0x4029000000000000); // 12.5
   realInTest("(BZ,F18.0)", "              125 ", 0x4093880000000000); // 1250
+  realInTest("(BZ,F18.0)", "       125 . e +1 ", 0x42a6bcc41e900000); // 1.25e13
   realInTest("(DC,F18.0)", "              12,5", 0x4029000000000000);
 
   listInputTest();