WIP: Start implementing new allocator

CMakeLists.txt

@@ -81,6 +81,7 @@ set(
     GL/texture.c
     GL/util.c
     GL/yalloc/yalloc.c
+    GL/alloc/alloc.c
     ${CMAKE_CURRENT_BINARY_DIR}/version.c
 )
 

GL/alloc/alloc.c

@@ -0,0 +1,228 @@
+#include <stdint.h>
+
+#include "alloc.h"
+
+
+/* This allocator is designed so that all allocations larger
+ * than 2k, fall on a 2k boundary. Smaller allocations will
+ * never cross a 2k boundary.
+ *
+ * House keeping is stored in RAM to avoid reading back from the
+ * VRAM to check for usage. Headers can't be easily stored in the
+ * blocks anyway as they have to be 2k aligned (so you'd need to
+ * store them in reverse or something)
+ *
+ * Defragmenting the pool will move allocations less than 2k
+ * first, and then shift any full 2k blocks to the start of the
+ * address space.
+ *
+ * The maximum pool size is 8M, made up of:
+ *
+ * - 4096 blocks of 2k
+ * - each with 8 sub-blocks of 256 bytes
+ *
+ * Why?
+ *
+ * The PVR performs better if textures don't cross 2K memory
+ * addresses, so we try to avoid that. Obviously we can't
+ * if the allocation is > 2k, but in that case we can at least
+ * align with 2k and the VQ codebook (which is usually 2k) will
+ * be in its own page.
+ *
+ * The smallest PVR texture allowed is 8x8 at 16 bit (so 128 bytes)
+ * but we're unlikely to use too many of those, so having a min sub-block
+ * size of 256 should be OK (a 16x16 image is 512, so two sub-blocks).
+ *
+ * We could go down to 128 bytes if wastage is an issue, but then we have
+ * to store double the number of usage markers.
+ */
+
+#include <assert.h>
+
+#define EIGHT_MEG (8 * 1024 * 1024)
+#define TWO_KILOBYTES (2 * 1024)
+#define BLOCK_COUNT (EIGHT_MEG / TWO_KILOBYTES)
+
+static inline int round_up(int n, int multiple)
+{
+    assert(multiple);
+    return ((n + multiple - 1) / multiple) * multiple;
+}
+
+struct AllocEntry {
+    void* pointer;
+    size_t size;
+    struct AllocEntry* next;
+};
+
+
+typedef struct {
+    /* This is a usage bitmask for each block. A block
+     * is divided into 8 x 256 byte subblocks. If a block
+     * is entirely used, it's value will be 255, if
+     * it's entirely free then it will be 0.
+     */
+    uint8_t block_usage[BLOCK_COUNT];
+    uint8_t* pool;  // Pointer to the memory pool
+    size_t pool_size; // Size of the memory pool
+    uint8_t* base_address; // First 2k aligned address in the pool
+    size_t block_count;  // Number of 2k blocks in the pool
+
+    /* It's frustrating that we need to do this dynamically
+     * but we need to know the size allocated when we free() */
+    struct AllocEntry* allocations;
+} PoolHeader;
+
+
+static PoolHeader pool_header = {
+    {0}, NULL, 0, NULL, 0, NULL
+};
+
+void* alloc_base_address(void* pool) {
+    return pool_header.base_address;
+}
+
+size_t alloc_block_count(void* pool) {
+    return pool_header.block_count;
+}
+
+void* alloc_next_available(void* pool, size_t required_size) {
+    uint8_t* it = pool_header.block_usage;
+    uint32_t required_subblocks = (required_size / 256);
+    if(required_size % 256) required_subblocks += 1;
+
+    while(true) {
+        // Skip full blocks
+        while((*it) == 255) {
+            ++it;
+            if(it >= pool_header.block_usage + sizeof(pool_header.block_usage)) {
+                return NULL;
+            }
+            continue;
+        }
+
+        uint32_t found_subblocks = 0;
+        bool requires_alignment = required_size >= 2048;
+
+        /* We just need to find enough consecutive blocks */
+        while(found_subblocks < required_subblocks) {
+            uint8_t t = *it;
+
+            /* Optimisation only. Skip over full blocks */
+            if(t == 255) {
+                ++it;
+                found_subblocks = 0;
+                continue;
+            }
+
+            /* Now let's see how many consecutive blocks we can find */
+            for(int i = 0; i < 8; ++i) {
+                if((t & 0x80) == 0) {
+                    if(requires_alignment && found_subblocks == 0 && i != 0) {
+                        // Ignore this subblock, because we want the first subblock to be aligned
+                        // at a 2048 boundary and this one isn't (i != 0)
+                        found_subblocks = 0;
+                    } else {
+                        found_subblocks++;
+                        if(found_subblocks >= required_subblocks) {
+                            /* We found space! Now calculate the address */
+                            uintptr_t offset = (it - pool_header.block_usage) * 8;
+                            offset += (i + 1);
+                            offset -= required_subblocks;
+                            return pool_header.base_address + (offset * 256);
+                        }
+                    }
+                } else {
+                    found_subblocks = 0;
+                }
+
+                t <<= 1;
+            }
+
+            ++it;
+            if(it >= pool_header.block_usage + sizeof(pool_header.block_usage)) {
+                return NULL;
+            }
+        }
+
+    }
+
+}
+
+uint32_t alloc_block_from_address(void* p) {
+
+}
+
+int alloc_init(void* pool, size_t size) {
+    if(pool_header.pool) {
+        return -1;
+    }
+
+    if(size > EIGHT_MEG) {  // FIXME: >= ?
+        return -1;
+    }
+
+    uint8_t* p = (uint8_t*) pool;
+
+    memset(pool_header.block_usage, 0, sizeof(pool_header.block_usage));
+    pool_header.pool = pool;
+    pool_header.pool_size = size;
+    pool_header.base_address = round_up(pool_header.pool, 2048);
+    pool_header.block_count = ((p + size) - pool_header.base_address) / 2048;
+
+    return 0;
+}
+
+void alloc_shutdown(void* pool) {
+    pool_header.pool = NULL;
+}
+
+void* alloc_malloc(void* pool, size_t size) {
+    void* ret = alloc_next_available(pool, size);
+    if(ret) {
+        uintptr_t start_subblock = (uint8_t*) ret - pool_header.base_address;
+
+        uint32_t required_subblocks = (size / 256);
+        if(size % 256) required_subblocks += 1;
+
+        uintptr_t start_block = start_subblock / 8;
+        uintptr_t filled_blocks = required_subblocks / 8;
+        uintptr_t trailing_subblocks = required_subblocks % 8;
+
+        for(size_t i = start_block; i < start_block + filled_blocks; ++i) {
+            pool_header.block_usage[i] = 255;
+        }
+
+        uint8_t* trailing = &pool_header.block_usage[start_block + filled_blocks];
+        uint8_t mask = 0;
+        for(size_t i = 0; i < trailing_subblocks; ++i) {
+            mask |= 1;
+            mask <<= 1;
+        }
+
+        mask <<= 8 - trailing_subblocks - 1;
+        *trailing |= mask;
+    }
+
+    return ret;
+}
+
+void alloc_free(void* pool, void* p) {
+
+}
+
+void alloc_defrag_start(void* pool) {
+
+}
+
+void* alloc_defrag_address(void* pool, void* p) {
+
+}
+
+void alloc_defrag_commit(void* pool) {
+
+}
+
+bool alloc_defrag_in_progress(void* pool) {
+
+}

GL/alloc/alloc.h

@@ -0,0 +1,28 @@
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+int alloc_init(void* pool, size_t size);
+void alloc_shutdown(void* pool);
+
+void *alloc_malloc(void* pool, size_t size);
+void alloc_free(void* pool, void* p);
+
+void alloc_defrag_start(void* pool);
+void* alloc_defrag_address(void* pool, void* p);
+void alloc_defrag_commit(void* pool);
+bool alloc_defrag_in_progress(void* pool);
+
+void* alloc_next_available(void* pool, size_t required_size);
+void* alloc_base_address(void* pool);
+size_t alloc_block_count(void* pool);
+
+#ifdef __cplusplus
+}
+#endif

tests/CMakeLists.txt

@@ -16,7 +16,7 @@ ADD_CUSTOM_COMMAND(
 add_executable(gldc_tests ${TEST_FILES} ${TEST_SOURCES} ${TEST_MAIN_FILENAME})
 target_link_libraries(gldc_tests GLdc)
 
-if(!PLATFORM_DREAMCAST)
+if(NOT PLATFORM_DREAMCAST)
 set_target_properties(
     gldc_tests
     PROPERTIES