[astc] Decode directly into color_values_direct[] (no intermediate result_vector storage)

src/video_core/host_shaders/astc_decoder.comp

@@ -83,6 +83,12 @@ int result_index = 0;
 uint result_vector_max_index;
 bool result_limit_reached = false;
 
+// avoid intermediate result_vector storage during color decode phase
+bool write_color_values = false;
+uint color_values_direct[32];
+uint color_out_index = 0;
+uint color_num_values = 0;
+
 // EncodingData helpers
 uint Encoding(EncodingData val) {
     return bitfieldExtract(val.data, 0, 8);
@@ -114,9 +120,110 @@ EncodingData CreateEncodingData(uint encoding, uint num_bits, uint bit_val, uint
     return EncodingData(((encoding) << 0u) | ((num_bits) << 8u) |
                         ((bit_val) << 16u) | ((quint_trit_val) << 24u));
 }
+uint ReplicateBitTo9(uint bit);
+uint FastReplicateTo8(uint value, uint num_bits);
+
+void EmitColorValue(EncodingData val) {
+    // write directly to color_values_direct[]
+    const uint encoding = Encoding(val);
+    const uint bitlen = NumBits(val);
+    const uint bitval = BitValue(val);
+
+    if (encoding == JUST_BITS) {
+        color_values_direct[++color_out_index] = FastReplicateTo8(bitval, bitlen);
+        return;
+    }
+
+    uint A = ReplicateBitTo9((bitval & 1));
+    uint B = 0, C = 0, D = QuintTritValue(val);
+
+    if (encoding == TRIT) {
+        switch (bitlen) {
+            case 1:
+            C = 204;
+            break;
+            case 2: {
+                C = 93;
+                const uint b = (bitval >> 1) & 1;
+                B = (b << 8) | (b << 4) | (b << 2) | (b << 1);
+                break;
+            }
+            case 3: {
+                C = 44;
+                const uint cb = (bitval >> 1) & 3;
+                B = (cb << 7) | (cb << 2) | cb;
+                break;
+            }
+            case 4: {
+                C = 22;
+                const uint dcb = (bitval >> 1) & 7;
+                B = (dcb << 6) | dcb;
+                break;
+            }
+            case 5: {
+                C = 11;
+                const uint edcb = (bitval >> 1) & 0xF;
+                B = (edcb << 5) | (edcb >> 2);
+                break;
+            }
+            case 6: {
+                C = 5;
+                const uint fedcb = (bitval >> 1) & 0x1F;
+                B = (fedcb << 4) | (fedcb >> 4);
+                break;
+            }
+        }
+    } else { // QUINT
+        switch (bitlen) {
+            case 1:
+            C = 113;
+            break;
+            case 2: {
+                C = 54;
+                const uint b = (bitval >> 1) & 1;
+                B = (b << 8) | (b << 3) | (b << 2);
+                break;
+            }
+            case 3: {
+                C = 26;
+                const uint cb = (bitval >> 1) & 3;
+                B = (cb << 7) | (cb << 1) | (cb >> 1);
+                break;
+            }
+            case 4: {
+                C = 13;
+                const uint dcb = (bitval >> 1) & 7;
+                B = (dcb << 6) | (dcb >> 1);
+                break;
+            }
+            case 5: {
+                C = 6;
+                const uint edcb = (bitval >> 1) & 0xF;
+                B = (edcb << 5) | (edcb >> 3);
+                break;
+            }
+        }
+    }
+
+    uint T = (D * C) + B;
+    T ^= A;
+    T = (A & 0x80) | (T >> 2);
+    color_values_direct[++color_out_index] = T;
+}
+
 
 
 void ResultEmplaceBack(EncodingData val) {
+    if (write_color_values) {
+        if (color_out_index >= color_num_values) {
+            // avoid decoding more than needed by this phase
+            result_limit_reached = true;
+            return;
+        }
+        EmitColorValue(val);
+        return;
+    }
+
     if (result_index >= result_vector_max_index) {
         // Alert callers to avoid decoding more than needed by this phase
         result_limit_reached = true;
@@ -457,7 +564,7 @@ void DecodeIntegerSequence(uint max_range, uint num_values) {
     }
 }
 
-void DecodeColorValues(uvec4 modes, uint num_partitions, uint color_data_bits, out uint color_values[32]) {
+void DecodeColorValues(uvec4 modes, uint num_partitions, uint color_data_bits) {
     uint num_values = 0;
     for (uint i = 0; i < num_partitions; i++) {
         num_values += ((modes[i] >> 2) + 1) << 1;
@@ -471,104 +578,21 @@ void DecodeColorValues(uvec4 modes, uint num_partitions, uint color_data_bits, o
             break;
         }
     }
-    DecodeIntegerSequence(range - 1, num_values);
+    // Decode directly into color_values_direct[]
-    uint out_index = 0;
+    write_color_values = true;
-    for (int itr = 0; itr < result_index; ++itr) {
+    color_out_index = 0;
-        if (out_index >= num_values) {
+    color_num_values = num_values;
-            break;
+    for (uint i = 0; i < 32; ++i) {
-        }
+        color_values_direct[i] = 0;
-        const EncodingData val = GetEncodingFromVector(itr);
-        const uint encoding = Encoding(val);
-        const uint bitlen = NumBits(val);
-        const uint bitval = BitValue(val);
-        uint A = 0, B = 0, C = 0, D = 0;
-        A = ReplicateBitTo9((bitval & 1));
-        switch (encoding) {
-        case JUST_BITS:
-            color_values[++out_index] = FastReplicateTo8(bitval, bitlen);
-            break;
-        case TRIT: {
-            D = QuintTritValue(val);
-            switch (bitlen) {
-            case 1:
-                C = 204;
-                break;
-            case 2: {
-                C = 93;
-                const uint b = (bitval >> 1) & 1;
-                B = (b << 8) | (b << 4) | (b << 2) | (b << 1);
-                break;
-            }
-            case 3: {
-                C = 44;
-                const uint cb = (bitval >> 1) & 3;
-                B = (cb << 7) | (cb << 2) | cb;
-                break;
-            }
-            case 4: {
-                C = 22;
-                const uint dcb = (bitval >> 1) & 7;
-                B = (dcb << 6) | dcb;
-                break;
-            }
-            case 5: {
-                C = 11;
-                const uint edcb = (bitval >> 1) & 0xF;
-                B = (edcb << 5) | (edcb >> 2);
-                break;
-            }
-            case 6: {
-                C = 5;
-                const uint fedcb = (bitval >> 1) & 0x1F;
-                B = (fedcb << 4) | (fedcb >> 4);
-                break;
-            }
-            }
-            break;
-        }
-        case QUINT: {
-            D = QuintTritValue(val);
-            switch (bitlen) {
-            case 1:
-                C = 113;
-                break;
-            case 2: {
-                C = 54;
-                const uint b = (bitval >> 1) & 1;
-                B = (b << 8) | (b << 3) | (b << 2);
-                break;
-            }
-            case 3: {
-                C = 26;
-                const uint cb = (bitval >> 1) & 3;
-                B = (cb << 7) | (cb << 1) | (cb >> 1);
-                break;
-            }
-            case 4: {
-                C = 13;
-                const uint dcb = (bitval >> 1) & 7;
-                B = (dcb << 6) | (dcb >> 1);
-                break;
-            }
-            case 5: {
-                C = 6;
-                const uint edcb = (bitval >> 1) & 0xF;
-                B = (edcb << 5) | (edcb >> 3);
-                break;
-            }
-            }
-            break;
-        }
-        }
-        if (encoding != JUST_BITS) {
-            uint T = (D * C) + B;
-            T ^= A;
-            T = (A & 0x80) | (T >> 2);
-            color_values[++out_index] = T;
-        }
     }
+
+    DecodeIntegerSequence(range - 1, num_values);
+
+    write_color_values = false;
 }
 
+
+
 ivec2 BitTransferSigned(int a, int b) {
     ivec2 transferred;
     transferred.y = b >> 1;
@@ -1069,13 +1093,12 @@ void DecompressBlock(ivec3 coord) {
     uvec4 endpoints0[4];
     uvec4 endpoints1[4];
     {
-        // This decode phase should at most push 32 elements into the vector
+        // Decode directly into color_values_direct[] (no intermediate result_vector storage)
-        result_vector_max_index = 32;
+        result_limit_reached = false;
-        uint color_values[32];
         uint colvals_index = 0;
-        DecodeColorValues(color_endpoint_mode, num_partitions, color_data_bits, color_values);
+        DecodeColorValues(color_endpoint_mode, num_partitions, color_data_bits);
         for (uint i = 0; i < num_partitions; i++) {
-            ComputeEndpoints(endpoints0[i], endpoints1[i], color_endpoint_mode[i], color_values,
+            ComputeEndpoints(endpoints0[i], endpoints1[i], color_endpoint_mode[i], color_values_direct,
                              colvals_index);
         }
     }