vc4: Use NIR texture lowering for texture swizzling.

We can't use its other features currently (mostly because we don't want
Newton-Raphson on rcps for texture coordinates), but it gets us started.

This eliminates some comparisons with constants in GLB2.7 and ETQW traces
at the QIR level by moving the comparisons into NIR, where they get
constant-folded out.

instructions in affected programs:     165 -> 156 (-5.45%)
total uniforms in shared programs: 32087 -> 32085 (-0.01%)
total estimated cycles in shared programs: 245762 -> 245752 (-0.00%)
estimated cycles in affected programs:     461 -> 451 (-2.17%)

2 files changed, 63 insertions, 57 deletions

diff --git a/src/gallium/drivers/vc4/vc4_program.c b/src/gallium/drivers/vc4/vc4_program.c
index c24aa19e74e..9d686f72877 100644
--- a/src/gallium/drivers/vc4/vc4_program.c
+++ b/src/gallium/drivers/vc4/vc4_program.c
@@ -123,26 +123,6 @@ nir_ssa_def *vc4_nir_get_state_uniform(struct nir_builder *b,
         return &intr->dest.ssa;
 }
 
-nir_ssa_def *
-vc4_nir_get_swizzled_channel(nir_builder *b, nir_ssa_def **srcs, int swiz)
-{
-        switch (swiz) {
-        default:
-        case UTIL_FORMAT_SWIZZLE_NONE:
-                fprintf(stderr, "warning: unknown swizzle\n");
-                /* FALLTHROUGH */
-        case UTIL_FORMAT_SWIZZLE_0:
-                return nir_imm_float(b, 0.0);
-        case UTIL_FORMAT_SWIZZLE_1:
-                return nir_imm_float(b, 1.0);
-        case UTIL_FORMAT_SWIZZLE_X:
-        case UTIL_FORMAT_SWIZZLE_Y:
-        case UTIL_FORMAT_SWIZZLE_Z:
-        case UTIL_FORMAT_SWIZZLE_W:
-                return srcs[swiz];
-        }
-}
-
 static struct qreg *
 ntq_init_ssa_def(struct vc4_compile *c, nir_ssa_def *def)
 {
@@ -338,30 +318,15 @@ ntq_emit_txf(struct vc4_compile *c, nir_tex_instr *instr)
         struct qreg tex = qir_TEX_RESULT(c);
         c->num_texture_samples++;
 
-        struct qreg texture_output[4];
+        struct qreg *dest = ntq_get_dest(c, &instr->dest);
         enum pipe_format format = c->key->tex[unit].format;
         if (util_format_is_depth_or_stencil(format)) {
                 struct qreg scaled = ntq_scale_depth_texture(c, tex);
                 for (int i = 0; i < 4; i++)
-                        texture_output[i] = scaled;
+                        dest[i] = scaled;
         } else {
-                struct qreg tex_result_unpacked[4];
                 for (int i = 0; i < 4; i++)
-                        tex_result_unpacked[i] = qir_UNPACK_8_F(c, tex, i);
-
-                const uint8_t *format_swiz =
-                        vc4_get_format_swizzle(c->key->tex[unit].format);
-                for (int i = 0; i < 4; i++) {
-                        texture_output[i] =
-                                get_swizzled_channel(c, tex_result_unpacked,
-                                                     format_swiz[i]);
-                }
-        }
-
-        struct qreg *dest = ntq_get_dest(c, &instr->dest);
-        for (int i = 0; i < 4; i++) {
-                dest[i] = get_swizzled_channel(c, texture_output,
-                                               c->key->tex[unit].swizzle[i]);
+                        dest[i] = qir_UNPACK_8_F(c, tex, i);
         }
 }
 
@@ -470,7 +435,7 @@ ntq_emit_tex(struct vc4_compile *c, nir_tex_instr *instr)
 
         enum pipe_format format = c->key->tex[unit].format;
 
-        struct qreg unpacked[4];
+        struct qreg *dest = ntq_get_dest(c, &instr->dest);
         if (util_format_is_depth_or_stencil(format)) {
                 struct qreg normalized = ntq_scale_depth_texture(c, tex);
                 struct qreg depth_output;
@@ -518,29 +483,15 @@ ntq_emit_tex(struct vc4_compile *c, nir_tex_instr *instr)
                 }
 
                 for (int i = 0; i < 4; i++)
-                        unpacked[i] = depth_output;
+                        dest[i] = depth_output;
         } else {
                 for (int i = 0; i < 4; i++)
-                        unpacked[i] = qir_UNPACK_8_F(c, tex, i);
+                        dest[i] = qir_UNPACK_8_F(c, tex, i);
         }
 
-        const uint8_t *format_swiz = vc4_get_format_swizzle(format);
-        struct qreg texture_output[4];
         for (int i = 0; i < 4; i++) {
-                texture_output[i] = get_swizzled_channel(c, unpacked,
-                                                         format_swiz[i]);
-        }
-
-        if (util_format_is_srgb(format)) {
-                for (int i = 0; i < 3; i++)
-                        texture_output[i] = qir_srgb_decode(c,
-                                                            texture_output[i]);
-        }
-
-        struct qreg *dest = ntq_get_dest(c, &instr->dest);
-        for (int i = 0; i < 4; i++) {
-                dest[i] = get_swizzled_channel(c, texture_output,
-                                               c->key->tex[unit].swizzle[i]);
+                if (c->tex_srgb_decode[unit] & (1 << i))
+                        dest[i] = qir_srgb_decode(c, dest[i]);
         }
 }
 
@@ -1805,6 +1756,56 @@ vc4_shader_ntq(struct vc4_context *vc4, enum qstage stage,
         if (stage == QSTAGE_FRAG)
                 vc4_nir_lower_blend(c);
 
+        struct nir_lower_tex_options tex_options = {
+                /* We would need to implement txs, but we don't want the
+                 * int/float conversions
+                 */
+                .lower_rect = false,
+
+                /* We want to use this, but we don't want to newton-raphson
+                 * its rcp.
+                 */
+                .lower_txp = false,
+
+                /* Apply swizzles to all samplers. */
+                .swizzle_result = ~0,
+        };
+
+        /* Lower the format swizzle and ARB_texture_swizzle-style swizzle.
+         * The format swizzling applies before sRGB decode, and
+         * ARB_texture_swizzle is the last thing before returning the sample.
+         */
+        for (int i = 0; i < ARRAY_SIZE(key->tex); i++) {
+                enum pipe_format format = c->key->tex[i].format;
+
+                if (!format)
+                        continue;
+
+                const uint8_t *format_swizzle = vc4_get_format_swizzle(format);
+
+                for (int j = 0; j < 4; j++) {
+                        uint8_t arb_swiz = c->key->tex[i].swizzle[j];
+
+                        if (arb_swiz <= 3) {
+                                tex_options.swizzles[i][j] =
+                                        format_swizzle[arb_swiz];
+                        } else {
+                                tex_options.swizzles[i][j] = arb_swiz;
+                        }
+
+                        /* If ARB_texture_swizzle is reading from the R, G, or
+                         * B channels of an sRGB texture, then we need to
+                         * apply sRGB decode to this channel at sample time.
+                         */
+                        if (arb_swiz < 3 && util_format_is_srgb(format)) {
+                                c->tex_srgb_decode[i] |= (1 << j);
+                        }
+
+                }
+        }
+
+        nir_lower_tex(c->s, &tex_options);
+
         if (c->fs_key && c->fs_key->light_twoside)
                 nir_lower_two_sided_color(c->s);
 
diff --git a/src/gallium/drivers/vc4/vc4_qir.h b/src/gallium/drivers/vc4/vc4_qir.h
index 9dad80dddff..4ab4d35d0ca 100644
--- a/src/gallium/drivers/vc4/vc4_qir.h
+++ b/src/gallium/drivers/vc4/vc4_qir.h
@@ -369,6 +369,11 @@ struct vc4_compile {
 
         uint8_t vattr_sizes[8];
 
+        /* Bitfield for whether a given channel of a sampler needs sRGB
+         * decode.
+         */
+        uint8_t tex_srgb_decode[VC4_MAX_TEXTURE_SAMPLERS];
+
         /**
          * Array of the VARYING_SLOT_* of all FS QFILE_VARY reads.
          *