llvmpipe: Fix attribute interpolation setup when rendering lines with msaa

If multisampling is enabled, we effectively always use pixel offset 0 for the
purposes of setup, overriding half pixel center.
However, line setup (and by the looks of it rectangle as well), while honoring
this for the purposes of setting up the rasterization planes, it forgot to
do this adjustment when setting up attribute interpolation, hence attribute
interpolation for lines ended up wrong.
Rather than fixing this up in line setup, just override pixel_offset in setup
context when using msaa, since this is what we actually do, which simplifies
the logic (do the same for the key for the setup jit function as well).

Reviewed-by: Brian Paul <brian.paul@broadcom.com>
Reviewed-by: Lucas Fryzek <lfryzek@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36435>

src/gallium/drivers/llvmpipe/lp_setup.c

@@ -585,7 +585,7 @@ lp_setup_bind_rasterizer(struct lp_setup_context *setup,
    setup->triangle = first_triangle;
    setup->rect = first_rectangle;
    setup->multisample = rast->multisample;
-   setup->pixel_offset = rast->half_pixel_center ? 0.5f : 0.0f;
+   setup->pixel_offset = !rast->multisample && rast->half_pixel_center ? 0.5f : 0.0f;
    setup->bottom_edge_rule = rast->bottom_edge_rule;
 
    if (setup->scissor_test != rast->scissor) {

src/gallium/drivers/llvmpipe/lp_setup_line.c

@@ -336,7 +336,7 @@ try_setup_line(struct lp_setup_context *setup,
    info.v1 = v1;
    info.v2 = v2;
 
-   const float pixel_offset = setup->multisample ? 0.0 : setup->pixel_offset;
+   const float pixel_offset = setup->pixel_offset;
 
    int x[4], y[4];
    if (setup->rectangular_lines) {

src/gallium/drivers/llvmpipe/lp_setup_point.c

@@ -115,7 +115,7 @@ texcoord_coef(struct lp_setup_context *setup,
 
    assert(i < 4);
 
-   const float pixel_offset = setup->multisample ? 0.0 : setup->pixel_offset;
+   const float pixel_offset = setup->pixel_offset;
    if (i == 0) {
       float dadx = FIXED_ONE / (float)info->dx12;
       float dady =  0.0f;
@@ -343,7 +343,7 @@ try_setup_point(struct lp_setup_context *setup,
     * slightly different rounding.
     */
    const int adj = (setup->bottom_edge_rule != 0) ? 1 : 0;
-   const float pixel_offset = setup->multisample ? 0.0 : setup->pixel_offset;
+   const float pixel_offset = setup->pixel_offset;
    struct lp_scene *scene = setup->scene;
    int x[2], y[2];
 

src/gallium/drivers/llvmpipe/lp_setup_tri.c

@@ -1040,7 +1040,7 @@ calc_fixed_position(struct lp_setup_context *setup,
                     const float (*v1)[4],
                     const float (*v2)[4])
 {
-   float pixel_offset = setup->multisample ? 0.0 : setup->pixel_offset;
+   float pixel_offset = setup->pixel_offset;
    /*
     * The rounding may not be quite the same with DETECT_ARCH_SSE
     * (util_iround right now only does nearest/even on x87,

src/gallium/drivers/llvmpipe/lp_state_setup.c

@@ -566,7 +566,7 @@ init_args(struct gallivm_state *gallivm,
    load_attribute(gallivm, args, key, 0, attr_pos);
 
    pixel_center = lp_build_const_vec(gallivm, typef4,
-                                     (!key->multisample && key->pixel_center_half) ? 0.5 : 0.0);
+                                     key->pixel_center_half ? 0.5 : 0.0);
 
    /*
     * xy are first two elems in v0a/v1a/v2a but just use vec4 arit
@@ -774,15 +774,15 @@ lp_make_setup_variant_key(const struct llvmpipe_context *lp,
                           struct lp_setup_variant_key *key)
 {
    const struct lp_fragment_shader *fs = lp->fs;
+   const struct pipe_rasterizer_state *rast = lp->rasterizer;
    struct nir_shader *nir = fs->base.ir.nir;
 
    assert(sizeof key->inputs[0] == sizeof(uint));
 
    key->num_inputs = nir->num_inputs;
-   key->flatshade_first = lp->rasterizer->flatshade_first;
-   key->pixel_center_half = lp->rasterizer->half_pixel_center;
-   key->multisample = lp->rasterizer->multisample;
-   key->twoside = lp->rasterizer->light_twoside;
+   key->flatshade_first = rast->flatshade_first;
+   key->pixel_center_half = rast->half_pixel_center && !rast->multisample;
+   key->twoside = rast->light_twoside;
    key->size = offsetof(struct lp_setup_variant_key, inputs[key->num_inputs]);
 
    key->color_slot = lp->color_slot[0];
@@ -795,23 +795,23 @@ lp_make_setup_variant_key(const struct llvmpipe_context *lp,
     * to the primitive's maximum Z value. Retain the original depth bias
     * value until that stage.
     */
-   key->floating_point_depth = lp->floating_point_depth && !lp->rasterizer->offset_units_unscaled;
+   key->floating_point_depth = lp->floating_point_depth && !rast->offset_units_unscaled;
 
-   key->pgon_offset_units = (float) lp->rasterizer->offset_units;
-   if (lp->rasterizer->offset_units != 0 && !lp->floating_point_depth &&
-       !lp->rasterizer->offset_units_unscaled) {
+   key->pgon_offset_units = (float) rast->offset_units;
+   if (rast->offset_units != 0 && !lp->floating_point_depth &&
+       !rast->offset_units_unscaled) {
       /* Ensure correct rounding if a unorm format is used. */
       float adjustment =
          lp->floating_point_depth
          ? 0
-         : (lp->rasterizer->offset_units > 0 ? 0.5 : -0.5);
+         : (rast->offset_units > 0.0f ? 0.5f : -0.5f);
 
       key->pgon_offset_units =
-         (float) ((lp->rasterizer->offset_units + adjustment) * lp->mrd);
+         (float) ((rast->offset_units + adjustment) * lp->mrd);
    }
 
-   key->pgon_offset_scale = lp->rasterizer->offset_scale;
-   key->pgon_offset_clamp = lp->rasterizer->offset_clamp;
+   key->pgon_offset_scale = rast->offset_scale;
+   key->pgon_offset_clamp = rast->offset_clamp;
    key->uses_constant_interp = 0;
    key->pad = 0;
 
@@ -819,7 +819,7 @@ lp_make_setup_variant_key(const struct llvmpipe_context *lp,
 
    for (unsigned i = 0; i < key->num_inputs; i++) {
       if (key->inputs[i].interp == LP_INTERP_COLOR) {
-         if (lp->rasterizer->flatshade)
+         if (rast->flatshade)
             key->inputs[i].interp = LP_INTERP_CONSTANT;
          else
             key->inputs[i].interp = LP_INTERP_PERSPECTIVE;

src/gallium/drivers/llvmpipe/lp_state_setup.h

@@ -26,7 +26,6 @@ struct lp_setup_variant_key {
    unsigned twoside:1;
    unsigned floating_point_depth:1;
    unsigned uses_constant_interp:1;
-   unsigned multisample:1;
    unsigned pad:3;
 
    /* TODO: get those floats out of the key and use a jit_context for setup */