sh: fix memcpy saving/restoring FR12-FR15 registers

This patch fixes a bug in the memcpy that doesn't save/restore
the FR12-FR15 registers (callee save registers in ST40 ABI) while
copying many cache lines with FPU in single paired precision mode
and by using all FPU registers (DR and XD).

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Reviewed-by: Carmelo Amoroso <carmelo.amoroso@st.com>

Signed-off-by: Carmelo Amoroso <carmelo.amoroso@st.com>

libc/string/sh/sh4/memcpy.S

@@ -497,6 +497,12 @@ ENTRY(memcpy)
 	mov	r5, r6
 	add	#-0x80, r6	! prefetch head
 
+	! store FPU (in single precision mode, do not check R15 align).
+	fmov	fr12, @-r15
+	fmov	fr13, @-r15
+	fmov	fr14, @-r15
+	fmov	fr15, @-r15
+
 	FPU_SET_PAIRED_PREC
 
 	mov	#4, r0
@@ -553,16 +559,22 @@ ENTRY(memcpy)
 	bt/s	67b
 	 pref	@r6
 
+	RESTORE_FPSCR
+
+	! Restore FPU callee save registers
+	fmov	@r15+, fr15
+	fmov	@r15+, fr14
+	fmov	@r15+, fr13
+	fmov	@r15+, fr12
+
 	! Other cache lines could be copied: so use the FPU in single paired
 	! precision without prefetching. No check for alignment is necessary.
 
 	mov	#1, r0
 	cmp/ge	r0, r3
-	bt/s	4f
+	bt/s	3f
 	 add	#0x60, r5
 
-	RESTORE_FPSCR
-
 	bra	5f
 	 nop