From: "Daniel Glastonbury" <dang@ratbaggames.com>
To: <gcc@gcc.gnu.org>
Subject: Teaching GCC about fmadd variant
Date: Mon, 22 Apr 2002 01:27:00 -0000 [thread overview]
Message-ID: <082e01c1e9d6$197bc720$7d00a8c0@dang2> (raw)
Hi,
I'm looking for some help in teaching gcc how to use the fmadd variants
that my mips has. Unlike the mips IV madd instruction, this mips has a
variant that goes something like this:
mula fs, ft : ACC <- fs*ft
madda fs, ft : ACC <- ACC + fs*ft
madd fd, fs, ft: fd <- ACC + fs*ft
The problem is there is no general way to move to/from the ACC register.
I tried to teach gcc about a new register, the fp acc, and then specify insn
patterns to try match on a new register contraint, which I called F.
here are the example insn patterns I'm using:
(define_insn ""
[(set (match_operand:SF 0 "register_operand" "=f")
(plus:SF (mult:SF (match_operand:SF 1 "register_operand" "f")
(match_operand:SF 2 "register_operand" "f"))
(match_operand:SF 3 "register_operand" "F")))]
"TARGET_MIPS5900"
"madd.s\\t%0,%1,%2"
[(set_attr "type" "fmadd")
(set_attr "mode" "SF")
(set_attr "length" "1")])
(define_insn "R5900_maddas"
[(set (match_operand:SF 0 "register_operand" "=F")
(plus:SF (mult:SF (match_operand:SF 1 "register_operand" "f")
(match_operand:SF 2 "register_operand" "f"))
(match_operand:SF 3 "register_operand" "F")))]
"TARGET_MIPS5900"
"madda.s\\t%1,%2"
[(set_attr "type" "fmadd")
(set_attr "mode" "SF")
(set_attr "length" "1")])
(define_insn ""
[(set (match_operand:SF 0 "register_operand" "=F")
(mult:SF (match_operand:SF 1 "register_operand" "f")
(match_operand:SF 2 "register_operand" "f")))]
"TARGET_MIPS5900"
"mula.s\\t%1,%2"
[(set_attr "type" "fmadd")
(set_attr "mode" "SF")
(set_attr "length" "1")])
The problem is that I get an ICE because the compiler can't generate a
reload. I believe it's trying to load the computation from a regular
mult:SF into the ACC register.
Can anyone point me in the right direction. I've tried to glean as much
information as I could from the gcc internals manual, and from
mips.{c,h,md}, but I can't work out how to tell gcc to use a different
register.
I'm sorry if this is the wrong forum to ask this question.
thanks
Dan
--
Daniel Glastonbury, Senior Programmer, Ratbag Pty Ltd
Level 8, 63 Pirie Street, Adelaide, SA, Australia. 5000
T: +618 8223 5830 F: +618 8223 5746 W: http://www.ratbaggames.com
next reply other threads:[~2002-04-22 8:17 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-04-22 1:27 Daniel Glastonbury [this message]
2002-04-22 7:38 ` Daniel Jacobowitz
2002-04-23 5:43 ` Daniel Glastonbury
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