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

From: Chad
Subject: [Qemu-devel] Performance bug in tcg/i386 output:
Date: Sun, 8 Nov 2009 09:47:30 -0800

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...

- Chad

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