Re: [U-Boot] compiled failed when turned off gcc optimazition
Hi, experts: Would any expert fix this question? It seems related MOVW instruction's usuage when turning off gcc optimazition. If i just turned on -O1 or -O2, still failed to compile uboot code. Best wishes, ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] compiled failed when turned off gcc optimazition
On 07/01/2013 12:51 PM, Wolfgang Denk wrote: Dear Mike Dunn, In message 51d1c455.9010...@newsguy.com you wrote: But there's a good motivation for wanting to turn off optimization. I disagree here. If you are hunting down a problem, you want to be as close at the original code as possible. Disabling optimization is such a dramatic change to the generated code that you actually debug a different program. I guess it depends on what problem being debugged... I think your point is valid for things like tracking down race conditions or misbehaving hardware. But for more mundane problems like logical errors in the code, optimizations get in the way. It would be nice to be able to experiment with optimizations off. Just knowing that a particular problem still exists when unoptimized code is run will provide some clues. Single-stepping with a debugger at the C source level is almost useless. I've since gotten better at single-stepping at the assembly level while using the mixed c and assembly view of gdb. Hm... Did you read up the documentation, say [1], and try out these recommendations? [1] http://www.denx.de/wiki/view/DULG/DebuggingTricks No, but I will. Many thanks! Mike ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] compiled failed when turned off gcc optimazition
Hi Mike, On Wed, Jul 3, 2013 at 5:40 AM, Mike Dunn miked...@newsguy.com wrote: On 07/01/2013 12:51 PM, Wolfgang Denk wrote: Dear Mike Dunn, In message 51d1c455.9010...@newsguy.com you wrote: But there's a good motivation for wanting to turn off optimization. I disagree here. If you are hunting down a problem, you want to be as close at the original code as possible. Disabling optimization is such a dramatic change to the generated code that you actually debug a different program. I guess it depends on what problem being debugged... I think your point is valid for things like tracking down race conditions or misbehaving hardware. But for more mundane problems like logical errors in the code, optimizations get in the way. It would be nice to be able to experiment with optimizations off. Just knowing that a particular problem still exists when unoptimized code is run will provide some clues. Do be honest, I have never used an online debugger I have always found that a combination of hardware LEDs and printf's has been more than sufficient, particularly for mundane issues. I'll freely admit that an online debugger might been faster for me, but I just wanted to point out that there is more than one way to skin a cat. I also believe that the more onerous the debugging tool is (and it doesn't get more so than using the hardware LEDs) the more attention you pay to the code rather than the output ;) Regards, Graeme ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] compiled failed when turned off gcc optimazition
Dear tiger...@viatech.com.cn, In message fe7aded5c2218b4786c09cd97dc4c49f940...@exchbj02.viatech.com.bj you wrote: I tried to turn off gcc optimazition by changing config.mk file: OPTFLAGS= -O0 #-fomit-frame-pointer But failed to compile u-boot, it tipped: Don't do it, then. Q: why would you want to switch off optimization? That's almost always a bad idea... Best regards, Wolfgang Denk -- DENX Software Engineering GmbH, MD: Wolfgang Denk Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: w...@denx.de I have made mistakes, but have never made the mistake of claiming I never made one. - James G. Bennet ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] compiled failed when turned off gcc optimazition
Hi, Denk: During debug u-boot with JTAG tools, maybe turning off optimizations was recommended. Best wishes, -邮件原件- 发件人: Wolfgang Denk [mailto:w...@denx.de] 发送时间: 2013年7月1日 18:03 收件人: Tiger Liu 抄送: u-boot@lists.denx.de 主题: Re: [U-Boot] compiled failed when turned off gcc optimazition Dear tiger...@viatech.com.cn, In message fe7aded5c2218b4786c09cd97dc4c49f940...@exchbj02.viatech.com.bj you wrote: I tried to turn off gcc optimazition by changing config.mk file: OPTFLAGS= -O0 #-fomit-frame-pointer But failed to compile u-boot, it tipped: Don't do it, then. Q: why would you want to switch off optimization? That's almost always a bad idea... Best regards, Wolfgang Denk -- DENX Software Engineering GmbH, MD: Wolfgang Denk Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: w...@denx.de I have made mistakes, but have never made the mistake of claiming I never made one. - James G. Bennet ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] compiled failed when turned off gcc optimazition
Dear tiger...@viatech.com.cn, please do not top post / full quote. In message fe7aded5c2218b4786c09cd97dc4c49f940...@exchbj02.viatech.com.bj you wrote: During debug u-boot with JTAG tools, maybe turning off optimizations was recommended. Many people recommend many things. Even strange or non-working or incorrect or dangerous ones. Best regards, Wolfgang Denk -- DENX Software Engineering GmbH, MD: Wolfgang Denk Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: w...@denx.de There's no future in time travel. ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] compiled failed when turned off gcc optimazition
On 07/01/2013 04:37 AM, Wolfgang Denk wrote: Dear tiger...@viatech.com.cn, please do not top post / full quote. In message fe7aded5c2218b4786c09cd97dc4c49f940...@exchbj02.viatech.com.bj you wrote: During debug u-boot with JTAG tools, maybe turning off optimizations was recommended. Many people recommend many things. Even strange or non-working or incorrect or dangerous ones. A while back I tried this for the Linux kernel, with similiar results. I just let it go without investigating further, guessing that maybe some tricks with compiler directives were incompatible with turning off optimization. But there's a good motivation for wanting to turn off optimization. Single-stepping with a debugger at the C source level is almost useless. I've since gotten better at single-stepping at the assembly level while using the mixed c and assembly view of gdb. Mike ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
Re: [U-Boot] compiled failed when turned off gcc optimazition
Dear Mike Dunn, In message 51d1c455.9010...@newsguy.com you wrote: But there's a good motivation for wanting to turn off optimization. I disagree here. If you are hunting down a problem, you want to be as close at the original code as possible. Disabling optimization is such a dramatic change to the generated code that you actually debug a different program. Single-stepping with a debugger at the C source level is almost useless. I've since gotten better at single-stepping at the assembly level while using the mixed c and assembly view of gdb. Hm... Did you read up the documentation, say [1], and try out these recommendations? [1] http://www.denx.de/wiki/view/DULG/DebuggingTricks Best regards, Wolfgang Denk -- DENX Software Engineering GmbH, MD: Wolfgang Denk Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: w...@denx.de You've no idea of what a poor opinion I have of myself, and how little I deserve it. - W. S. Gilbert ___ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
