On Mon, Dec 10, 2018 at 12:42:40PM +0200, Eleni Maria Stea wrote: > Calculating the scissor rectangle fields with the y flipped (0 on top) > can generate negative values that will cause assertion failure later on > as the scissor fields are all unsigned. We must clamp the bbox values > again to make sure they don't exceed the fb_height. Also fixed a > calculation error. > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=108999
Good find. Could you send the test to the piglit list? > --- > src/mesa/drivers/dri/i965/genX_state_upload.c | 15 ++++++++++++++- > 1 file changed, 14 insertions(+), 1 deletion(-) > > diff --git a/src/mesa/drivers/dri/i965/genX_state_upload.c > b/src/mesa/drivers/dri/i965/genX_state_upload.c > index 8e3fcbf12e..5d8fc8214e 100644 > --- a/src/mesa/drivers/dri/i965/genX_state_upload.c > +++ b/src/mesa/drivers/dri/i965/genX_state_upload.c > @@ -2424,8 +2424,21 @@ set_scissor_bits(const struct gl_context *ctx, int i, > /* memory: Y=0=top */ > sc->ScissorRectangleXMin = bbox[0]; > sc->ScissorRectangleXMax = bbox[1] - 1; > + > + /* Clamping to fb_height is necessary because otherwise the > + * subtractions below would produce a negative result, which would > + * then be assigned to the unsigned YMin/YMax scissor fields, > + * resulting in an assertion failure in GENX(SCISSOR_RECT_pack) > + */ > + > + if (bbox[3] > fb_height) > + bbox[3] = fb_height; > + > + if (bbox[2] > fb_height) > + bbox[2] = fb_height; > + We should be able to fix this bug in a simpler manner by changing the MAX2 calls at the top of this function to CLAMP calls. > sc->ScissorRectangleYMin = fb_height - bbox[3]; > - sc->ScissorRectangleYMax = fb_height - bbox[2] - 1; > + sc->ScissorRectangleYMax = fb_height - (bbox[2] - 1); I don't think we want to start adding 1 instead of subtracting 1. The subtraction is there to satisfy the requirement for the HW packet. -Nanley > } > } > > -- > 2.20.0.rc2 > > _______________________________________________ > mesa-dev mailing list > mesa-dev@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/mesa-dev _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
