Running demos/glsl/twoside on RV770, using Using vert shader Two-sided lighting both sides are red, all is ok (red/green) using swrast/softpipe/llvmpipe.
Note: classic r600 driver has been abandoned. works correctly with r600g (gallium driver) on my rv770 tested with mesa git master e81ee67b51651e99e7e8e52c1ccafc66835d57cd and mesa 8.0.4
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