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Date: Sat, 29 May 2010 21:33:02 +0800 From: Changli Gao <xiaosuo@...il.com> To: Borislav Petkov <bp@...en8.de>, Changli Gao <xiaosuo@...il.com>, Alexander Viro <viro@...iv.linux.org.uk>, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 2/2] fs: optimize mpage_bio_submit() On Sat, May 29, 2010 at 8:47 PM, Borislav Petkov <bp@...en8.de> wrote: > > ok, can you sincerely tell me that your change makes the code more > readable? And have you checked to see what the compiler actually > "optimizes"? > > original code: > > movq $mpage_end_io_read, %rdx #, tmp65 > movq $mpage_end_io_write, %rax #, tmp64 > cmpl $1, %edi #, rw > cmovne %rdx, %rax # tmp65,, tmp64 > movq %rax, 80(%rsi) # tmp64, <variable>.bi_end_io > .loc 1 91 0 > call submit_bio # > > your change: > > movq $mpage_end_io_read, %rdx #, tmp63 > movq $mpage_end_io_write, %rax #, iftmp.561 > cmpl $1, %edi #, rw > cmovne %rdx, %rax # tmp63,, iftmp.561 > movq %rax, 80(%rsi) # iftmp.561, <variable>.bi_end_io > .loc 1 90 0 > call submit_bio # > > so that change does nothing except obfuscating the source a bit more so > that you get more headaches whenever you look at it. > Oh, I didn't check the asm code. Compiler is smarter than I thought. Thanks for your explaining. -- Regards， Changli Gao(xiaosuo@...il.com) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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