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[RFC] Kill bogosity in rtx_cost
- From: "David S. Miller" <davem at redhat dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Fri, 10 May 2002 08:54:53 -0700 (PDT)
- Subject: [RFC] Kill bogosity in rtx_cost
After talking over with Richard about some of the things
rtx_cost() does the other week we stumbled upon this turd.
It special cases multiplication by a power of 2 and gives
it a cost like a shift.
That doesn't make any sense. What CSE does is substitute,
simply the RTX expressions, _then_ compute costs.
Given that, this code should just be killed because it serves
not purpose other than confuse.
Any objections? If not I'll install this on the mainline.
2002-05-10 David S. Miller <firstname.lastname@example.org>
* cse.c (rtx_cost): Remove multiplication by power of 2 special
--- cse.c.~1~ Wed May 8 22:46:11 2002
+++ cse.c Fri May 10 09:01:02 2002
@@ -842,13 +842,7 @@ rtx_cost (x, outer_code)
- /* Count multiplication by 2**n as a shift,
- because if we are considering it, we would output it as a shift. */
- if (GET_CODE (XEXP (x, 1)) == CONST_INT
- && exact_log2 (INTVAL (XEXP (x, 1))) >= 0)
- total = 2;
- total = COSTS_N_INSNS (5);
+ total = COSTS_N_INSNS (5);