panfrost: Fix blend fixed-function prototype

Needs to be broken up into different functions for disjoint state.
Simpler prototypes and allows matching to CSOs.

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10869>

src/gallium/drivers/panfrost/pan_blend_cso.c

@@ -144,10 +144,16 @@ panfrost_get_blend_for_context(struct panfrost_context *ctx, unsigned rti, struc
                sizeof(pan_blend.constants));
 
         /* First, we'll try fixed function, matching equation and constant */
-        if (pan_blend_can_fixed_function(dev, &pan_blend, rti)) {
+        const struct pan_blend_equation eq = pan_blend.rts[rti].equation;
-                const struct pan_blend_equation eq = pan_blend.rts[rti].equation;
+        unsigned constant_mask = pan_blend_constant_mask(eq);
-                unsigned constant_mask = pan_blend_constant_mask(eq);
 
+        bool ff = pan_blend_can_fixed_function(eq);
+        ff &= pan_blend_is_homogenous_constant(constant_mask, ctx->blend_color.color);
+        ff &= (pan_blend_supports_constant(dev->arch, rti) || !constant_mask);
+        ff &= !pan_blend.logicop_enable;
+        ff &= panfrost_blendable_formats[fmt].internal;
+
+        if (ff) {
                 struct panfrost_blend_final final = {
                         .load_dest = pan_blend_reads_dest(pan_blend.rts[rti].equation),
                         .equation.constant = pan_blend_get_constant(constant_mask, ctx->blend_color.color),

src/panfrost/lib/pan_blend.c

@@ -86,61 +86,34 @@ pan_blend_constant_mask(const struct pan_blend_equation eq)
                blend_factor_constant_mask(eq.alpha_dst_factor);
 }
 
-static bool
+/* Only "homogenous" (scalar or vector with all components equal) constants are
-can_blend_constant(const struct panfrost_device *dev,
+ * valid for fixed-function, so check for this condition */
-                   const struct pan_blend_state *state,
+
-                   unsigned rt)
+bool
+pan_blend_is_homogenous_constant(unsigned mask, float *constants)
 {
-        unsigned constant_mask = pan_blend_constant_mask(state->rts[rt].equation);
+        float constant = pan_blend_get_constant(mask, constants);
-        if (!constant_mask)
-                return true;
 
-        /* v6 doesn't support blend constants in FF blend equations. */
+        u_foreach_bit(i, mask) {
-        if (dev->arch == 6)
+                if (constants[i] != constant)
-                return false;
-
-        /* v7 only uses the constant from RT 0 (TODO: what if it's the same
-         * constant? or a constant is shared?) */
-        if (dev->arch == 7 && rt > 0)
-                return false;
-
-        float constant = pan_blend_get_constant(constant_mask, state->constants);
-
-        u_foreach_bit(i, constant_mask) {
-                if (state->constants[i] != constant)
                         return false;
         }
 
         return true;
 }
 
+/* Determines if an equation can run in fixed function */
+
 bool
-pan_blend_can_fixed_function(const struct panfrost_device *dev,
+pan_blend_can_fixed_function(const struct pan_blend_equation equation)
-                             const struct pan_blend_state *state,
-                             unsigned rt)
 {
-        const struct pan_blend_rt_state *rt_state = &state->rts[rt];
+        return !equation.blend_enable ||
-
+               (can_fixed_function_equation(equation.rgb_func,
-        /* LogicOp requires a blend shader */
+                                            equation.rgb_src_factor,
-        if (state->logicop_enable)
+                                            equation.rgb_dst_factor) &&
-                return false;
+                can_fixed_function_equation(equation.alpha_func,
-
+                                            equation.alpha_src_factor,
-        /* Not all formats can be blended by fixed-function hardware */
+                                            equation.alpha_dst_factor));
-        if (!panfrost_blendable_formats[rt_state->format].internal)
-                return false;
-
-        if (!rt_state->equation.blend_enable)
-                return true;
-
-        if (!can_blend_constant(dev, state, rt))
-                return false;
-
-        return can_fixed_function_equation(rt_state->equation.rgb_func,
-                                           rt_state->equation.rgb_src_factor,
-                                           rt_state->equation.rgb_dst_factor) &&
-               can_fixed_function_equation(rt_state->equation.alpha_func,
-                                           rt_state->equation.alpha_src_factor,
-                                           rt_state->equation.alpha_dst_factor);
 }
 
 static enum mali_blend_operand_c
@@ -312,8 +285,6 @@ pan_blend_to_fixed_function_equation(ASSERTED const struct panfrost_device *dev,
 {
         const struct pan_blend_rt_state *rt_state = &state->rts[rt];
 
-        assert(pan_blend_can_fixed_function(dev, state, rt));
-
         /* If no blending is enabled, default back on `replace` mode */
         if (!rt_state->equation.blend_enable) {
                 equation->color_mask = rt_state->equation.color_mask;

src/panfrost/lib/pan_blend.h

@@ -100,9 +100,7 @@ bool
 pan_blend_reads_dest(const struct pan_blend_equation eq);
 
 bool
-pan_blend_can_fixed_function(const struct panfrost_device *dev,
+pan_blend_can_fixed_function(const struct pan_blend_equation equation);
-                             const struct pan_blend_state *state,
-                             unsigned rt);
 
 bool
 pan_blend_is_opaque(const struct pan_blend_equation eq);
@@ -120,6 +118,19 @@ pan_blend_get_constant(unsigned mask, float *constants)
         return mask ? constants[ffs(mask) - 1] : 0.0;
 }
 
+/* v6 doesn't support blend constants in FF blend equations whatsoever, and v7
+ * only uses the constant from RT 0 (TODO: what if it's the same constant? or a
+ * constant is shared?) */
+
+static inline bool
+pan_blend_supports_constant(unsigned arch, unsigned rt)
+{
+        return !((arch == 6) || (arch == 7 && rt > 0));
+}
+
+bool
+pan_blend_is_homogenous_constant(unsigned mask, float *constants);
+
 void
 pan_blend_to_fixed_function_equation(const struct panfrost_device *dev,
                                      const struct pan_blend_state *state,