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RE: [avr-chat] Missed Optimisation ?
From: |
Boyapati, Anitha |
Subject: |
RE: [avr-chat] Missed Optimisation ? |
Date: |
Wed, 2 Mar 2011 13:27:43 +0800 |
>
> result |= 0x80000000;
> 626: 80 91 5a 02 lds r24, 0x025A
> 62a: 90 91 5b 02 lds r25, 0x025B
> 62e: a0 91 5c 02 lds r26, 0x025C
> 632: b0 91 5d 02 lds r27, 0x025D
> 636: b0 68 ori r27, 0x80 ; 128
> 638: 80 93 5a 02 sts 0x025A, r24
> 63c: 90 93 5b 02 sts 0x025B, r25
> 640: a0 93 5c 02 sts 0x025C, r26
> 644: b0 93 5d 02 sts 0x025D, r27
>
>The compiler has loaded all 4 bytes of the uint32_t, but only operated
>on one of them, so it seems 'clever' enough to see that the immediate
>value is full of '0' and not bother to OR the lower bytes but still
>loads and saves them.
OK. I now get it. The question is why store the 'other' bytes when it is not
modified. Please ignore the other post where I thought why only 1 byte is being
'OR' ed.
Anitha
- Re: [avr-chat] Missed Optimisation ?, (continued)
- Re: [avr-chat] Missed Optimisation ?, Graham Davies, 2011/03/01
- Re: [avr-chat] Missed Optimisation ?, Erik Christiansen, 2011/03/01
- Re: [avr-chat] Missed Optimisation ?, bob, 2011/03/01
- Message not available
- [avr-chat] Re: Fasching, bob, 2011/03/02
- Re: [avr-chat] Re: Fasching, Erik Christiansen, 2011/03/02
- Re: [avr-chat] Missed Optimisation ?, Graham Davies, 2011/03/01
- RE: [avr-chat] Missed Optimisation ?, Colin O'Flynn, 2011/03/01
- Re: [avr-chat] Missed Optimisation ?, Graham Davies, 2011/03/01
- Re: [avr-chat] Missed Optimisation ?, Michael Hennebry, 2011/03/01
RE: [avr-chat] Missed Optimisation ?, Boyapati, Anitha, 2011/03/02
RE: [avr-chat] Missed Optimisation ?,
Boyapati, Anitha <=
Re: [avr-chat] Missed Optimisation ?, bob, 2011/03/01
Re: [avr-chat] Missed Optimisation ?, bob, 2011/03/01
Re: [avr-chat] Missed Optimisation ?, Graham Davies, 2011/03/01