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[Qemu-devel] TCG

From: Fabrice Bellard
Subject: [Qemu-devel] TCG
Date: Fri, 01 Feb 2008 14:13:12 +0100
User-agent: Thunderbird (X11/20070727)


I added a new code generator (TCG) in QEMU. Read the file qemu/tcg/README to have technical information. A new code generator was needed in order to avoid problems with the various GCC versions and to get better performance.

I made minimal modifications in each target so that they can still work by using TCG and legacy "dyngen" micro operations. More work will be needed to convert each target to TCG, but it can be done progressively. Only the x86 and x86_64 targets have been significantly modified to use TCG.

TCG currently only supports x86 and x86_64 hosts. The support of other hosts is broken in QEMU. I don't consider it is a priority to support other hosts although TCG is generic enough to allow it.

The performance should not change much at this point. On x86_64 hosts, the x86 and x86_64 targets are faster because of some assembly language optimizations. On x86 hosts, the x86_64 target is faster because TCG can do some optimizations related to the conversion from 64 to 32 bits. No performance change should be noticed on non x86 targets because they are not converted yet.


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