This is an obvious mini-optimization if the input operands of mulhi are the
same, one multiply operation can be saved.
Ok for trunk?
Johann
* config/avr/avr.md (*mulhi3_enh): Treat squaring smarter.
Index: config/avr/avr.md
===================================================================
--- config/avr/avr.md (revision 179738)
+++ config/avr/avr.md (working copy)
@@ -1560,13 +1560,11 @@ (define_insn "*mulhi3_enh"
(mult:HI (match_operand:HI 1 "register_operand" "r")
(match_operand:HI 2 "register_operand" "r")))]
"AVR_HAVE_MUL"
- "mul %A1,%A2
- movw %0,r0
- mul %A1,%B2
- add %B0,r0
- mul %B1,%A2
- add %B0,r0
- clr r1"
+ {
+ return REGNO (operands[1]) == REGNO (operands[2])
+ ? "mul %A1,%A1\;movw %0,r0\;mul %A1,%B1\;add %B0,r0\;add %B0,r0\;clr r1"
+ : "mul %A1,%A2\;movw %0,r0\;mul %A1,%B2\;add %B0,r0\;mul %B1,%A2\;add %B0,r0\;clr r1";
+ }
[(set_attr "length" "7")
(set_attr "cc" "clobber")])
