Apparently, special float8 comparison file for Alpha is only needed

tglsfdc · tglsfdc · commit ee6a91682dc1 · 2000-12-30T02:48:04.000Z
when using vendor cc, not gcc.
diff --git a/src/test/regress/resultmap b/src/test/regress/resultmap
@@ -9,7 +9,7 @@ float8/.*-bsdi=float8-small-is-zero
 float8/.*-freebsd=float8-small-is-zero
 float8/i.86-.*-netbsd=float8-small-is-zero
 float8/.*-qnx=float8-exp-three-digits
-float8/alpha.*-dec-osf=float8-fp-exception
+float8/alpha.*-dec-osf.*:cc=float8-fp-exception
 float8/i.86-pc-cygwin=float8-small-is-zero
 geometry/.*-bsdi=geometry-positive-zeros-bsd
 geometry/.*-darwin=geometry-powerpc-darwin
