[PATCH, PR61219]: Fix sNaN handling in ARM float to double conversion

[Aurelien Jarno]

On ARM soft-float, the float to double conversion doesn't convert a sNaN
to qNaN as the IEEE Std 754 standard mandates:

"Under default exception handling, any operation signaling an invalid
operation exception and for which a floating-point result is to be
delivered shall deliver a quiet NaN."

Given the soft float ARM code ignores exceptions and always provides a
result, a float to double conversion of a signaling NaN should return a
quiet NaN. Fix this in extendsfdf2.


2014-05-18  Aurelien Jarno  <aurelien@aurel32.net>
       
	PR target/61219
	* config/arm/ieee754-df.S (extendsfdf2): Convert sNaN to qNaN.


Index: libgcc/config/arm/ieee754-df.S
===================================================================
--- libgcc/config/arm/ieee754-df.S	(revision 210588)
+++ libgcc/config/arm/ieee754-df.S	(working copy)
@@ -473,11 +473,15 @@
 	eorne	xh, xh, #0x38000000	@ fixup exponent otherwise.
 	RETc(ne)			@ and return it.
 
-	teq	r2, #0			@ if actually 0
-	do_it	ne, e
-	teqne	r3, #0xff000000		@ or INF or NAN
+	bics	r2, r2, #0xff000000	@ isolate mantissa
+	do_it	eq			@ if 0, that is ZERO or INF,
 	RETc(eq)			@ we are done already.
 
+	teq	r3, #0xff000000		@ check for NAN
+	do_it	eq, t
+	orreq	xh, xh, #0x00080000	@ change to quiet NAN
+	RETc(eq)			@ and return it.
+
 	@ value was denormalized.  We can normalize it now.
 	do_push	{r4, r5, lr}
 	mov	r4, #0x380		@ setup corresponding exponent

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                 http://www.aurel32.net