NV2A VSH RAW Hazard

[mborgerson]

While hunting down graphical bugs in Halo 2, I observed the following VSH code emitted during the render of a tire on a warthog in Halo 2:

  /* Slot 33: 0x00000000 0x008240C0 0x842A5AFC 0xBC80C848 */
  MAD(R8,xy, R8.wx, c[18].xy, c[18].zw);
  MAD(oT0,xy, R8.wx, c[18].xy, c[18].zw);

This appears to be a clear read-after-write hazard for R8. As a temporary solution to this, I've moved the temporary write to follow the muxed write. We should re-evaluate the vsh generation code to look for other such issues.

xqemu/hw/xbox/nv2a/nv2a_vsh.c

Line 409 in 8d05bc9

qstring_append_fmt(ret, " %s(R%d%s%s);\n",

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Before:

After: