as in exp(), treat +/-Inf and NaN arguments specially, should fix

eg expf(-Inf) which was Nan previously
(We could avoid touching the i387 on amd64 in these cases, but we'd
need to bypass the ABI abstraction macros, so leave it the old way
for now.)

lib/libm/arch/i387/e_expf.S

@@ -8,11 +8,20 @@
 #include "abi.h"
 
 
-RCSID("$NetBSD: e_expf.S,v 1.5 2003/07/26 19:24:58 salo Exp $")
+RCSID("$NetBSD: e_expf.S,v 1.6 2008/06/24 17:27:56 drochner Exp $")
 
 /* e^x = 2^(x * log2(e)) */
 ENTRY(__ieee754_expf)
 	XMM_ONE_ARG_FLOAT_PROLOGUE
+
+	/*
+	 * catch +/-Inf and NaN arguments
+	 */
+	movl	ARG_FLOAT_ONE,%eax
+	andl	$0x7fffffff,%eax
+	cmpl	$0x7f800000,%eax
+	jae	x_Inf_or_NaN
+
 	flds	ARG_FLOAT_ONE
 	fldl2e
 	fmulp				/* x * log2(e) */
@@ -27,3 +36,20 @@ ENTRY(__ieee754_expf)
 	fstp	%st(1)
 	XMM_FLOAT_EPILOGUE
 	ret
+
+x_Inf_or_NaN:
+	/*
+	 * Return 0 if x is -Inf.  Otherwise just return x, although the
+	 * C version would return (x + x) (Real Indefinite) if x is a NaN.
+	 */
+	movl	ARG_FLOAT_ONE,%eax
+	cmpl	$0xff800000,%eax
+	jne	x_not_minus_Inf
+	fldz
+	XMM_FLOAT_EPILOGUE
+	ret
+
+x_not_minus_Inf:
+	flds	ARG_FLOAT_ONE
+	XMM_FLOAT_EPILOGUE
+	ret