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Hard ware long dooble operations are slower.
- To: gcc-help at gcc dot gnu dot org
- Subject: Hard ware long dooble operations are slower.
- From: "M.V.S. Phani Narasimham" <phanimvs at wipinfo dot soft dot net>
- Date: Thu, 30 Dec 1999 15:44:05 +0530 (IST)
- Reply-To: "M.V.S. Phani Narasimham" <phanimvs at wipinfo dot soft dot net>
hi,
Why quad floatine point instructions of sparcv9 are very slower,
compared to the instructions which make call to the library and
perform the operations.
The following c code takes more time when compiled with cc1 of gcc
with option -mhard-quad-float than when compiled with sun cc.
-----------------------------------------------------------
c code:-
1 main(){
2 long double a=2e0;
3 int i;
4 for(i=0;i<10000000;i++)
5 a=a+2;
6 printf("%Lfg\n",a);
7 }
The c code generates an faddq instruction.
----------------------------------------------------------------------
Time taken details:-
real 4m36.96s
user 0m23.33s
sys 1m8.59s
-------------------------------------------------------------------
If Sun cc is used it makes a call to the library (_Qp_add_)
and the details of the time are.
real 0m14.77s
user 0m5.01s
sys 0m0.01s
------------------------------------------------------------------
I could not see any trap handler that get's invoked when the hard quad
instructions are generated. Is it that they are implimented in the system
software or firmware. If so why is it slow.
phani.
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M.V.S. Phani Narasimham
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