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[Bug target/11180] [avr-gcc] Optimization decrease performance of struct assignment.
- From: "pinskia at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 9 Jan 2005 01:30:51 -0000
- Subject: [Bug target/11180] [avr-gcc] Optimization decrease performance of struct assignment.
- References: <20030613023559.11180.dmixm@marine.febras.ru>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Additional Comments From pinskia at gcc dot gnu dot org 2005-01-09 01:30 -------
One issue I find is that avr does not define_insn_and_split (or just define_split) which will greatly
improve the code generation because the hi part of the QI would be zero and you don't need to set it
four times.
ldi r25,hi8(2)
ldi r25,hi8(1)
ldi r26,hlo8(1)
ldi r27,hhi8(1)
The main difference between -Os and -O0 (at least before 4.0.0) is that we use more registers at -Os
which causes the prologue and eplogue to do more so my recommendation will help a lot.
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11180