lima: Implement scissor support

[PabloPL]

For scissor 0,0,0,0 we're skipping any drawings, for other cases it's calculated the same way as limadriver. Had to add support for tgsi shaders - it's done in the same way as vc4/freedreno (we can convert them from tgsi to nir) and use nir_opt_global_to_local and nir_lower_regs_to_ssa nir pass.

[PabloPL]

Still wasn't able to run gbm-surface-color, when i tried to enable scissors by adding

glEnable(GL_SCISSOR_TEST);
glScissor(0, 0, 0, 0); // or anything other than (0, 0, TARGET_SIZE, TARGET_SIZE)

In this case mesa is generating tgsi shader, so previously it was failing at assert(cso->type == PIPE_SHADER_IR_NIR);

Now it's complaining

gbm-surface: nir/nir_opt_undef.c:87: opt_undef_vecN: Assertion `alu->dest.dest.is_ssa' failed

Any ideas how to solve this? I don't have any mesa experience but wanted to gather some by looking at task "command stream setup for other OGL purpose like clear, blend, depth, and etc." from wiki. Looking at lima code, scissors should be easiest from them

[yuq]

You're welcome to work on this topic. As for this patch, it looks good to me. But I'll wait it be more complete before merge it, that means either this patch or a patch serial that finally achieve your goal to enable the scissor support.

This problem should be the original lima_program_optimize_vs_nir lima_program_optimize_fs_nir are not written for TGSI converted NIR, so may miss some pass for it, you can reference the vc4 vc4_shader_state_create for the additional pass like NIR_PASS_V(s, nir_opt_global_to_local); NIR_PASS_V(s, nir_lower_regs_to_ssa);

[yuq]

BTW. if we have to use NIR from TGSI, maybe we need to implement PIPE_CAP_TGSI_VS_LOWER_VIEWPORT_TRANSFORM in TGSI too, because I just add it for NIR only.

[yuq]

Do the two new commits finish your scissor support?

[PabloPL]

Adding nir_opt_global_to_local and nir_lower_regs_to_ssa pass to both fs and vs solved problem with compiling shader. But i found some problems with last patch and need to make more testing/work on it

• sometimes i'm getting plbu out of memory (lima 1c40000.gpu: gp error irq state=4000 status=3)
• even when i set in gbm-surface-color scissors to 0,0,0,0 mesa is calling lima_set_scissor_states with scissor min=0/256 max=0/256

[PabloPL]

PR rebased against 17.3.

[PabloPL]

About TGSI path - i wasn't able to reproduce it using gbm-surface-color, but was able to reproduce it using piglit tests (just compile piglit with libgbm installed and then run).

PIGLIT_PLATFORM=gbm ./bin/gl-1.0-scissor-copypixels -auto -fbo

I had to make following change in lima_screen.c

case PIPE_SHADER_CAP_MAX_TEXTURE_SAMPLERS:
      return 0; // return 16; /* need investigate */

(because we don't have yet create_sampler_view implemented and it was causing a crash).

[yuq]

Good, seems we may use piglit to get a TODO list for mesa-lima now. I'll merge your TGSI change for now and mark the TGSI viewport change later implement. But it should not bother your scissor patch test in gbm-surface-color. So please go ahead for the scissor patch fix.

[PabloPL]

What if in the second frame, the scissor is enabled but not changed, so this won't be dirty but still need be set?

By using rasterizer.scissor field to check if scissor test is enabled this is fixed. During testing (comparing with images generated using the same gbm-surface-move on intel gpu and lima) i've found that it's fixed. But there is issue with zero scissor with multiple frames. With following dummy change

+       if (si == 1) {
+               glScissor(0,0, 0, 0);
+               glEnable(GL_SCISSOR_TEST);
+       } else if (si == 4) {
+               glDisable(GL_SCISSOR_TEST);
+       }

        //glDrawElements(GL_TRIANGLES, sizeof(index)/sizeof(GLuint), GL_UNSIGNED_INT, index);
        glDrawArrays(GL_TRIANGLES, 0, 3);

On intel:

• frame0 -> triangle, no scissor
• frame1 -> empty screen, zero scissor
• frame2 -> empty screen, zero scissor
• frame3 -> empty screen, zero scissor
• frame4 -> triangle, no scissor On lima:
• frame0 -> triangle, no scissor
• frame1 -> triangle, no scissor
• frame2 -> empty screen, zero scissor
• frame3 -> empty screen, zero scissor
• frame4 -> triangle, no scissor

Again, need to work more on this...

[PabloPL]

For now i'm closing this PR (till all issues with scissor are fixed).