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Re: [Qemu-devel] Performance bug in tcg/i386 output:

From: Laurent Desnogues
Subject: Re: [Qemu-devel] Performance bug in tcg/i386 output:
Date: Sun, 8 Nov 2009 18:56:15 +0100

On Sun, Nov 8, 2009 at 6:47 PM, Chad <address@hidden> wrote:
> Running qemu[-i386] with -d out_asm and looking at qemu.out shows this
> test/j**/jmp pattern repeatedly:
> 0xb1aa40f6:  test   %ecx,%ecx
> 0xb1aa40f8:  jne    0xb1aa4115
> 0xb1aa40fe:  jmp    0xb1aa4103
> 0xb1aa4103:  mov    $0xc0bf,%eax
> Therefore there's a bug in the tcg generator creating many unnecessary
> jmps.  It might get optimized out by the CPU, but it might not and it bloats
> the asm output in any case...

Some of these jumps are patched later when the target
block is translated (block chaining).

If you want to see the real output, you'll have to disassemble
after execution.


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