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Re: [Qemu-devel] What's the difference between "ld/st" and "qemu_ld/st"


From: Richard Henderson
Subject: Re: [Qemu-devel] What's the difference between "ld/st" and "qemu_ld/st" in TCG IR?
Date: Sat, 23 May 2015 15:21:26 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0

On 05/23/2015 05:26 AM, 浩倫 魏 wrote:
So there are some points that I hope you can help me out:
1. Is every guest load/store instruction would be translated to qemu_ld/st IR?

Yes.

2. What about another TCG IR "ld/st"? What kind of guest instructions would
cause TCG generates that IRs and for what purpose?

For instance, vector instructions are often implemented without TCG temporaries, but instead using ld/st to load the data from the ENV pointer directly. You can see that in the ARM and i386 targets.

Otherwise, there are sometimes less-used system values that do not warrent a TCG temporary. You can see that in the alpha target.


r~



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