Richard: That is very intelligient way to support AVX. I believe Bochs uses similar technique.
On Wed, Jan 22, 2014 at 2:19 PM, Richard Henderson <r...@twiddle.net> wrote: > On 01/22/2014 11:35 AM, Xin Tong wrote: >> It seems that BOCHS have AVX instructions support in interpreter. I am >> thinking an easy/reliable way to do this would be generate helper >> calls to emulate every AVX instruction and follow how BOCHS emulates >> them. Then depending on the expected frequency and difficulties, one >> can decide whether to move some of the instructions into TCG JITted >> code ? >> >> Also, it would be desirable to use the MMX/SSE structures and >> functions that already exist in QEMU target-i386/translate.c > > The way you should start is by re-using the existing SSE helpers. > > There are several things one must consider with AVX: > > (1) Old SSE insns. These do not modify bits 128 and higher. > (2) SSE insns encoded with VEX. These zero bits 128 and higher. > (3) AVX insns. These (generally) modify all 256 bits. > > Case 1 can be handled by doing nothing with the existing helpers. > > Case 2 can be handled by using the existing helper, followed by a couple of > stores to zero the high part. > > Case 3 can, with only a few exceptions, be handled by using the existing > helper > twice on the two halves. Thankfully the existing helpers work with host > pointers rather than register numbers. > > That will cover at least 90% of the AVX2 instruction set. > > > r~
