diff mbox

[AVR] : Save instruction when squaring HI

Message ID 4E92BD4E.10007@gjlay.de
State New
Headers show

Commit Message

Georg-Johann Lay Oct. 10, 2011, 9:39 a.m. UTC 
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.
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Patch

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")])