[patch, pushed] AVR: Tweak __muldi3_6

[Georg-Johann Lay]

This patch changes __muldi3_6 to

__muldi3_6:
    XCALL   __umulhisi3
    add     C2, 22
    adc     C3, 23
    adc     C4, 24
    adc     C5, 25
    adc     C6, __zero_reg__
    adc     C7, __zero_reg__
    ret

which is one cycle faster than the previous

    ...
    adc     C5, 25
    brcc    0f
    adiw    C6, 1
0:  ret

in the case where the BRCC is not taken.
__umulhisi3 clears __zero_reg__, so all is fine.

libgcc/
        * config/avr/lib1funcs.S (__muldi3_6): Tweak.

diff --git a/libgcc/config/avr/lib1funcs.S b/libgcc/config/avr/lib1funcs.S
index 2e30c796ef9..f4143d44f00 100644
--- a/libgcc/config/avr/lib1funcs.S
+++ b/libgcc/config/avr/lib1funcs.S
@@ -802,9 +802,9 @@ DEFUN __muldi3_6
     adc     C3, 23
     adc     C4, 24
     adc     C5, 25
-    brcc    0f
-    adiw    C6, 1
-0:  ret
+    adc     C6, __zero_reg__
+    adc     C7, __zero_reg__
+    ret
 ENDF __muldi3_6
 #endif /* L_muldi3_6 */


Applied as obvious,

Johann