nir: Define system values for vc4's blending-lowering arguments.

In the GLSL-to-NIR conversion of VC4, I had a bit of trouble with what I
was calling the "state uniforms" that I was putting into the NIR fighting
with its other lowering passes.  Instead of using magic uniform base
numbers in the backend, follow the lead of load_user_clip_plane and just
define system values for them.

v2: Fix unintended change to channel_num, drop unspecified const_index
    value on blend_const_color_r_float.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/compiler/nir/nir_intrinsics.h

@@ -310,6 +310,15 @@ SYSTEM_VALUE(user_clip_plane, 4, 1, UCP_ID, xx, xx)
 SYSTEM_VALUE(num_work_groups, 3, 0, xx, xx, xx)
 SYSTEM_VALUE(helper_invocation, 1, 0, xx, xx, xx)
 SYSTEM_VALUE(channel_num, 1, 0, xx, xx, xx)
+SYSTEM_VALUE(alpha_ref_float, 1, 0, xx, xx, xx)
+
+/* Blend constant color values.  Float values are clamped. */
+SYSTEM_VALUE(blend_const_color_r_float, 1, 0, xx, xx, xx)
+SYSTEM_VALUE(blend_const_color_g_float, 1, 0, xx, xx, xx)
+SYSTEM_VALUE(blend_const_color_b_float, 1, 0, xx, xx, xx)
+SYSTEM_VALUE(blend_const_color_a_float, 1, 0, xx, xx, xx)
+SYSTEM_VALUE(blend_const_color_rgba8888_unorm, 1, 0, xx, xx, xx)
+SYSTEM_VALUE(blend_const_color_aaaa8888_unorm, 1, 0, xx, xx, xx)
 
 /**
  * Barycentric coordinate intrinsics.

src/gallium/drivers/vc4/vc4_nir_lower_blend.c

@@ -127,9 +127,12 @@ vc4_blend_channel_f(nir_builder *b,
                         return nir_imm_float(b, 1.0);
                 }
         case PIPE_BLENDFACTOR_CONST_COLOR:
-                return vc4_nir_get_state_uniform(b, QUNIFORM_BLEND_CONST_COLOR_X + channel);
+                return nir_load_system_value(b,
+                                             nir_intrinsic_load_blend_const_color_r_float +
+                                             channel,
+                                             0);
         case PIPE_BLENDFACTOR_CONST_ALPHA:
-                return vc4_nir_get_state_uniform(b, QUNIFORM_BLEND_CONST_COLOR_W);
+                return nir_load_blend_const_color_a_float(b);
         case PIPE_BLENDFACTOR_ZERO:
                 return nir_imm_float(b, 0.0);
         case PIPE_BLENDFACTOR_INV_SRC_COLOR:
@@ -142,10 +145,13 @@ vc4_blend_channel_f(nir_builder *b,
                 return nir_fsub(b, nir_imm_float(b, 1.0), dst[channel]);
         case PIPE_BLENDFACTOR_INV_CONST_COLOR:
                 return nir_fsub(b, nir_imm_float(b, 1.0),
-                                vc4_nir_get_state_uniform(b, QUNIFORM_BLEND_CONST_COLOR_X + channel));
+                                nir_load_system_value(b,
+                                                      nir_intrinsic_load_blend_const_color_r_float +
+                                                      channel,
+                                                      0));
         case PIPE_BLENDFACTOR_INV_CONST_ALPHA:
                 return nir_fsub(b, nir_imm_float(b, 1.0),
-                                vc4_nir_get_state_uniform(b, QUNIFORM_BLEND_CONST_COLOR_W));
+                                nir_load_blend_const_color_a_float(b));
 
         default:
         case PIPE_BLENDFACTOR_SRC1_COLOR:
@@ -196,9 +202,9 @@ vc4_blend_channel_i(nir_builder *b,
                                                nir_imm_int(b, ~0),
                                                a_chan);
         case PIPE_BLENDFACTOR_CONST_COLOR:
-                return vc4_nir_get_state_uniform(b, QUNIFORM_BLEND_CONST_COLOR_RGBA);
+                return nir_load_blend_const_color_rgba8888_unorm(b);
         case PIPE_BLENDFACTOR_CONST_ALPHA:
-                return vc4_nir_get_state_uniform(b, QUNIFORM_BLEND_CONST_COLOR_AAAA);
+                return nir_load_blend_const_color_aaaa8888_unorm(b);
         case PIPE_BLENDFACTOR_ZERO:
                 return nir_imm_int(b, 0);
         case PIPE_BLENDFACTOR_INV_SRC_COLOR:
@@ -210,9 +216,11 @@ vc4_blend_channel_i(nir_builder *b,
         case PIPE_BLENDFACTOR_INV_DST_COLOR:
                 return nir_inot(b, dst);
         case PIPE_BLENDFACTOR_INV_CONST_COLOR:
-                return nir_inot(b, vc4_nir_get_state_uniform(b, QUNIFORM_BLEND_CONST_COLOR_RGBA));
+                return nir_inot(b,
+                                nir_load_blend_const_color_rgba8888_unorm(b));
         case PIPE_BLENDFACTOR_INV_CONST_ALPHA:
-                return nir_inot(b, vc4_nir_get_state_uniform(b, QUNIFORM_BLEND_CONST_COLOR_AAAA));
+                return nir_inot(b,
+                                nir_load_blend_const_color_aaaa8888_unorm(b));
 
         default:
         case PIPE_BLENDFACTOR_SRC1_COLOR:
@@ -475,11 +483,10 @@ vc4_nir_emit_alpha_test_discard(struct vc4_compile *c, nir_builder *b,
         if (!c->fs_key->alpha_test)
                 return;
 
-        nir_ssa_def *alpha_ref =
-                vc4_nir_get_state_uniform(b, QUNIFORM_ALPHA_REF);
         nir_ssa_def *condition =
                 vc4_nir_pipe_compare_func(b, c->fs_key->alpha_test_func,
-                                          alpha, alpha_ref);
+                                          alpha,
+                                          nir_load_alpha_ref_float(b));
 
         nir_intrinsic_instr *discard =
                 nir_intrinsic_instr_create(b->shader,

src/gallium/drivers/vc4/vc4_nir_lower_io.c

@@ -342,11 +342,13 @@ vc4_nir_lower_uniform(struct vc4_compile *c, nir_builder *b,
                 intr_comp->num_components = 1;
                 nir_ssa_dest_init(&intr_comp->instr, &intr_comp->dest, 1, 32, NULL);
 
-                /* Convert the uniform offset to bytes.  If it happens to be a
+                /* Convert the uniform offset to bytes.  If it happens
-                 * constant, constant-folding will clean up the shift for us.
+                 * to be a constant, constant-folding will clean up
+                 * the shift for us.
                  */
                 nir_intrinsic_set_base(intr_comp,
-                                       nir_intrinsic_base(intr) * 16 + i * 4);
+                                       nir_intrinsic_base(intr) * 16 +
+                                       i * 4);
 
                 intr_comp->src[0] =
                         nir_src_for_ssa(nir_ishl(b, intr->src[0].ssa,

src/gallium/drivers/vc4/vc4_program.c

@@ -110,21 +110,6 @@ indirect_uniform_load(struct vc4_compile *c, nir_intrinsic_instr *intr)
         return qir_TEX_RESULT(c);
 }
 
-nir_ssa_def *vc4_nir_get_state_uniform(struct nir_builder *b,
-                                       enum quniform_contents contents)
-{
-        nir_intrinsic_instr *intr =
-                nir_intrinsic_instr_create(b->shader,
-                                           nir_intrinsic_load_uniform);
-        nir_intrinsic_set_base(intr,
-                               (VC4_NIR_STATE_UNIFORM_OFFSET + contents) * 4);
-        intr->num_components = 1;
-        intr->src[0] = nir_src_for_ssa(nir_imm_int(b, 0));
-        nir_ssa_dest_init(&intr->instr, &intr->dest, 1, 32, NULL);
-        nir_builder_instr_insert(b, &intr->instr);
-        return &intr->dest.ssa;
-}
-
 nir_ssa_def *
 vc4_nir_get_swizzled_channel(nir_builder *b, nir_ssa_def **srcs, int swiz)
 {
@@ -1567,16 +1552,9 @@ ntq_emit_intrinsic(struct vc4_compile *c, nir_intrinsic_instr *instr)
                         assert(offset % 4 == 0);
                         /* We need dwords */
                         offset = offset / 4;
-                        if (offset < VC4_NIR_STATE_UNIFORM_OFFSET) {
+                        ntq_store_dest(c, &instr->dest, 0,
-                                ntq_store_dest(c, &instr->dest, 0,
+                                       qir_uniform(c, QUNIFORM_UNIFORM,
-                                               qir_uniform(c, QUNIFORM_UNIFORM,
+                                                   offset));
-                                                           offset));
-                        } else {
-                                ntq_store_dest(c, &instr->dest, 0,
-                                               qir_uniform(c, offset -
-                                                           VC4_NIR_STATE_UNIFORM_OFFSET,
-                                                           0));
-                        }
                 } else {
                         ntq_store_dest(c, &instr->dest, 0,
                                        indirect_uniform_load(c, instr));
@@ -1592,6 +1570,34 @@ ntq_emit_intrinsic(struct vc4_compile *c, nir_intrinsic_instr *instr)
                 }
                 break;
 
+        case nir_intrinsic_load_blend_const_color_r_float:
+        case nir_intrinsic_load_blend_const_color_g_float:
+        case nir_intrinsic_load_blend_const_color_b_float:
+        case nir_intrinsic_load_blend_const_color_a_float:
+                ntq_store_dest(c, &instr->dest, 0,
+                               qir_uniform(c, QUNIFORM_BLEND_CONST_COLOR_X +
+                                           (instr->intrinsic -
+                                            nir_intrinsic_load_blend_const_color_r_float),
+                                           0));
+                break;
+
+        case nir_intrinsic_load_blend_const_color_rgba8888_unorm:
+                ntq_store_dest(c, &instr->dest, 0,
+                               qir_uniform(c, QUNIFORM_BLEND_CONST_COLOR_RGBA,
+                                           0));
+                break;
+
+        case nir_intrinsic_load_blend_const_color_aaaa8888_unorm:
+                ntq_store_dest(c, &instr->dest, 0,
+                               qir_uniform(c, QUNIFORM_BLEND_CONST_COLOR_AAAA,
+                                           0));
+                break;
+
+        case nir_intrinsic_load_alpha_ref_float:
+                ntq_store_dest(c, &instr->dest, 0,
+                               qir_uniform(c, QUNIFORM_ALPHA_REF, 0));
+                break;
+
         case nir_intrinsic_load_sample_mask_in:
                 ntq_store_dest(c, &instr->dest, 0,
                                qir_uniform(c, QUNIFORM_SAMPLE_MASK, 0));

src/gallium/drivers/vc4/vc4_qir.h

@@ -505,11 +505,6 @@ struct vc4_compile {
 
 #define VC4_NIR_MS_MASK_OUTPUT			2000000000
 
-/* Special offset for nir_load_uniform values to get a QUNIFORM_*
- * state-dependent value.
- */
-#define VC4_NIR_STATE_UNIFORM_OFFSET		1000000000
-
 struct vc4_compile *qir_compile_init(void);
 void qir_compile_destroy(struct vc4_compile *c);
 struct qblock *qir_new_block(struct vc4_compile *c);
@@ -566,8 +561,6 @@ bool qir_opt_small_immediates(struct vc4_compile *c);
 bool qir_opt_vpm(struct vc4_compile *c);
 void vc4_nir_lower_blend(nir_shader *s, struct vc4_compile *c);
 void vc4_nir_lower_io(nir_shader *s, struct vc4_compile *c);
-nir_ssa_def *vc4_nir_get_state_uniform(struct nir_builder *b,
-                                       enum quniform_contents contents);
 nir_ssa_def *vc4_nir_get_swizzled_channel(struct nir_builder *b,
                                           nir_ssa_def **srcs, int swiz);
 void vc4_nir_lower_txf_ms(nir_shader *s, struct vc4_compile *c);