Add some regression test cases for denormalized float8 input.

This was submitted with the previous patch, but I'm committing it
separately to ease backing it out if these results prove too unportable.

Marti Raudsepp, after a proposal by Jeroen Vermeulen

src/test/regress/expected/float8-exp-three-digits-win32.out

@@ -24,6 +24,25 @@ SELECT '-10e-400'::float8;
 ERROR:  "-10e-400" is out of range for type double precision
 LINE 1: SELECT '-10e-400'::float8;
                ^
+-- test whether denormalized values are accepted
+SELECT '4.95e-324'::float8 < '1.49e-323'::float8;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT '4.95e-324'::float8 > '0'::float8;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT substr('-4.95e-324'::float8::text, 1, 4);
+ substr 
+--------
+ -4.9
+(1 row)
+
 -- bad input
 INSERT INTO FLOAT8_TBL(f1) VALUES ('');
 ERROR:  invalid input syntax for type double precision: ""

src/test/regress/expected/float8-small-is-zero.out

@@ -24,6 +24,25 @@ SELECT '10e-400'::float8;
 
 SELECT '-10e-400'::float8;
  float8 
+-- test whether denormalized values are accepted
+SELECT '4.95e-324'::float8 < '1.49e-323'::float8;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT '4.95e-324'::float8 > '0'::float8;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT substr('-4.95e-324'::float8::text, 1, 4);
+ substr 
+--------
+ -4.9
+(1 row)
+
 --------
      -0
 (1 row)

src/test/regress/expected/float8-small-is-zero_1.out

@@ -24,6 +24,25 @@ SELECT '10e-400'::float8;
 
 SELECT '-10e-400'::float8;
  float8 
+-- test whether denormalized values are accepted
+SELECT '4.95e-324'::float8 < '1.49e-323'::float8;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT '4.95e-324'::float8 > '0'::float8;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT substr('-4.95e-324'::float8::text, 1, 4);
+ substr 
+--------
+ -4.9
+(1 row)
+
 --------
       0
 (1 row)

src/test/regress/expected/float8.out

@@ -24,6 +24,25 @@ SELECT '-10e-400'::float8;
 ERROR:  "-10e-400" is out of range for type double precision
 LINE 1: SELECT '-10e-400'::float8;
                ^
+-- test whether denormalized values are accepted
+SELECT '4.95e-324'::float8 < '1.49e-323'::float8;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT '4.95e-324'::float8 > '0'::float8;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT substr('-4.95e-324'::float8::text, 1, 4);
+ substr 
+--------
+ -4.9
+(1 row)
+
 -- bad input
 INSERT INTO FLOAT8_TBL(f1) VALUES ('');
 ERROR:  invalid input syntax for type double precision: ""

src/test/regress/sql/float8.sql

@@ -16,6 +16,11 @@ SELECT '-10e400'::float8;
 SELECT '10e-400'::float8;
 SELECT '-10e-400'::float8;
 
+-- test whether denormalized values are accepted
+SELECT '4.95e-324'::float8 < '1.49e-323'::float8;
+SELECT '4.95e-324'::float8 > '0'::float8;
+SELECT substr('-4.95e-324'::float8::text, 1, 4);
+
 -- bad input
 INSERT INTO FLOAT8_TBL(f1) VALUES ('');
 INSERT INTO FLOAT8_TBL(f1) VALUES ('     ');