temporary commit

Signed-off-by: Ronald Caesar <github43132@proton.me>

CMakeLists.txt

@@ -97,7 +97,6 @@ add_executable(Pound
 
 add_subdirectory(3rd_Party)
 add_subdirectory(src/common)
-add_subdirectory(src/frontend)
 add_subdirectory(src/host)
 add_subdirectory(src/jit)
 add_subdirectory(src/pvm)
@@ -110,7 +109,7 @@ add_subdirectory(src/targets/switch1/hardware)
 include(TestBigEndian)
 TEST_BIG_ENDIAN(WORDS_BIGENDIAN)
 
-list(APPEND POUND_PROJECT_TARGETS common frontend host pvm)
+list(APPEND POUND_PROJECT_TARGETS common host pvm)
 foreach(TARGET ${POUND_PROJECT_TARGETS})
     # Apply Endianness definitions to all our targets.
     if(WORDS_BIGENDIAN)
@@ -149,7 +148,6 @@ set_property(TARGET Pound PROPERTY CMAKE_INTERPROCEDURAL_OPTIMIZATION_RELEASE TR
 
 target_link_libraries(Pound PRIVATE
     common
-    frontend
     host
     jit
     pvm

src/jit/decoder/arm32.cpp

@@ -9,7 +9,8 @@ namespace pound::jit::decoder
 {
 /* Increase value as more instructions get implemented */
 #define INSTRUCTION_ARRAY_CAPACITY 4
-arm32_decoder_t g_arm32_decoder = {};
+
+#define HASH_TABLE_INVALID_INDEX 0xFFFF
 
 /*
  * ============================================================================
@@ -18,9 +19,11 @@ arm32_decoder_t g_arm32_decoder = {};
  */
 void arm32_add_instruction(arm32_decoder_t* decoder, const char* name, const char* bitstring, arm32_handler_fn handler);
 void arm32_ADD_imm_handler(arm32_decoder_t* decoder, arm32_instruction_t instruction);
+void arm32_SUB_imm_handler(arm32_decoder_t* decoder, arm32_instruction_t instruction);
 
 void arm32_parse_bitstring(const char* bitstring, uint32_t* mask, uint32_t* expected);
 void arm32_grow_instructions_array(arm32_decoder_t* decoder, size_t new_capacity);
+uint32_t arm32_generate_hash_seed(uint32_t mask, uint32_t expected);
 
 /*
  * ============================================================================
@@ -38,7 +41,7 @@ void arm32_init(pound::host::memory::arena_t allocator, arm32_decoder_t* decoder
     /* Setup Instructions array.*/
     size_t instructions_array_size = INSTRUCTION_ARRAY_CAPACITY * sizeof(arm32_instruction_info_t);
     PVM_ASSERT(instructions_array_size <= decoder->allocator.capacity);
-    LOG_TRACE("Growing instructions array to %d bytes", instructions_array_size);
+    LOG_TRACE("Allocated %d bytes to instructions array", instructions_array_size);
 
     void* new_ptr = pound::host::memory::arena_allocate(&decoder->allocator, instructions_array_size);
     PVM_ASSERT(nullptr != new_ptr);
@@ -50,8 +53,97 @@ void arm32_init(pound::host::memory::arena_t allocator, arm32_decoder_t* decoder
 #define INST(fn, name, bitstring) arm32_add_instruction(decoder, name, bitstring, &arm32_##fn##_handler);
 #include "./arm32.inc"
 #undef INST
+
+    LOG_TRACE("Initializing perfect hash parameters for %zu instructions", decoder->instruction_count);
+
+    /* Start with table size as next power of 2 >= count * 2 */
+    uint16_t table_size = 1U;
+    while (table_size < decoder->instruction_count * 2)
+    {
+        table_size <<= 1U;
+    }
+
+    uint16_t mask = table_size - 1;
+    size_t slots_used_size = table_size * sizeof(bool);
+    bool* slots_used = (bool*)pound::host::memory::arena_allocate(&decoder->allocator, slots_used_size);
+    PVM_ASSERT(nullptr != slots_used);
+    LOG_TRACE("Allocated %d bytes to hash slots used array", slots_used_size);
+
+    uint16_t shift = 0;
+    bool perfect_hash_generated = false;
+    for (; shift < 16; ++shift)
+    {
+        bool collision_free = true;
+        (void)memset(slots_used, false, slots_used_size);
+
+        uint16_t hash;
+        for (size_t i = 0; i < decoder->instruction_count; ++i)
+        {
+            uint32_t hash_seed =
+                arm32_generate_hash_seed(decoder->instructions[i].mask, decoder->instructions[i].expected);
+
+            /*
+             * Now we need to convert the 32-bit hash seed into an index within our hash table.
+             * We right shift by `shift` bits. Different shift values produce different hash distributions. We found
+             * the shift value that ensures no two instructions map to the same hash table slot.
+             */
+            hash = ((hash_seed >> shift) & mask);
+            if (true == slots_used[hash])
+            {
+                LOG_TRACE("Instruction %s: Collision detected at slot %u for shift %u", decoder->instructions[i].name,
+                          hash, shift);
+                collision_free = false;
+                break;
+            }
+            slots_used[hash] = true;
+            LOG_TRACE("Instruction %s: Collision-free hash %u found for shift %u", decoder->instructions[i].name, hash,
+                      shift);
+        }
+        if (true == collision_free)
+        {
+            perfect_hash_generated = true;
+            break;
+        }
+    }
+
+    PVM_ASSERT_MSG(true == perfect_hash_generated, "Failed to generate perfect hash - no collision-free hash found");
+    LOG_TRACE("Perfect hash parameters: shift=%u, mask=0x%04x, table_size=%u", shift, mask, table_size);
+
+    size_t hash_table_size = table_size * sizeof(uint16_t);
+    uint16_t* hash_table = (uint16_t*)pound::host::memory::arena_allocate(&decoder->allocator, hash_table_size);
+    PVM_ASSERT(nullptr != hash_table);
+    LOG_TRACE("Allocated %zu bytes to hash table", hash_table_size);
+
+    /* Initialize hash table with invalid indices */
+    for (size_t i = 0; i < table_size; ++i)
+    {
+        hash_table[i] = HASH_TABLE_INVALID_INDEX;
+    }
+
+    for (size_t i = 0; i < decoder->instruction_count; ++i)
+    {
+        uint32_t hash_seed = arm32_generate_hash_seed(decoder->instructions[i].mask, decoder->instructions[i].expected);
+        uint32_t hash = (hash_seed >> shift) & mask;
+        PVM_ASSERT_MSG(HASH_TABLE_INVALID_INDEX == hash_table[hash], "Hash collision detected");
+
+        PVM_ASSERT(i < 0xFFFF);
+        hash_table[hash] = (uint16_t)i;
+
+        LOG_TRACE("Instruction '%s' hashed to slot %u", decoder->instructions[i].name, hash);
+    }
+
+    decoder->perfect_hash.hash_shift = shift;
+    decoder->perfect_hash.hash_mask = mask;
+    decoder->perfect_hash.table_size = table_size;
+    decoder->perfect_hash.hash_table = hash_table;
 }
 
+/*
+ * ============================================================================
+ *                          Private Functions
+ * ============================================================================
+ */
+
 void arm32_add_instruction(arm32_decoder_t* decoder, const char* name, const char* bitstring, arm32_handler_fn handler)
 {
     PVM_ASSERT(nullptr != decoder);
@@ -71,33 +163,17 @@ void arm32_add_instruction(arm32_decoder_t* decoder, const char* name, const cha
     info->handler = handler;
 
     /* Calculate priority based on number of fixed bits. */
-    info->priority = 0;
-    for (int i = 0; i < 32; ++i)
-    {
-        if ((mask >> i) & 1)
-        {
-            ++info->priority;
-        }
-    }
-
+    info->priority = (uint8_t)__builtin_popcount(mask);
     ++decoder->instruction_count;
-    LOG_TRACE("========================================");
+
     LOG_TRACE("Instruction Registered: %s", info->name);
     LOG_TRACE("Mask:      0x%08X", info->mask);
     LOG_TRACE("Expected:  0x%08X", info->expected);
     LOG_TRACE("Priority:  %d", info->priority);
-    LOG_TRACE("========================================");
-
-
-    /* TODO(GloriousTacoo:jit): Add instruction to lookup table. */
 }
-void arm32_ADD_imm_handler(arm32_decoder_t* decoder, arm32_instruction_t instruction) {}
 
-/*
- * ============================================================================
- *                          Private Functions
- * ============================================================================
- */
+void arm32_ADD_imm_handler(arm32_decoder_t* decoder, arm32_instruction_t instruction) {}
+void arm32_SUB_imm_handler(arm32_decoder_t* decoder, arm32_instruction_t instruction) {}
 
 void arm32_parse_bitstring(const char* bitstring, uint32_t* mask, uint32_t* expected)
 {
@@ -109,7 +185,7 @@ void arm32_parse_bitstring(const char* bitstring, uint32_t* mask, uint32_t* expe
     *mask = 0;
     *expected = 0;
     uint8_t instruction_size_bits = 32;
-    for (int i = 0; (i < instruction_size_bits) && (bitstring[i] != '\0'); ++i)
+    for (unsigned int i = 0; (i < instruction_size_bits) && (bitstring[i] != '\0'); ++i)
     {
         uint32_t bit_position = 31 - i;
         switch (bitstring[i])
@@ -134,5 +210,34 @@ void arm32_parse_bitstring(const char* bitstring, uint32_t* mask, uint32_t* expe
         }
     }
 }
+uint32_t arm32_generate_hash_seed(uint32_t mask, uint32_t expected)
+{
+    /* 
+             * XOR combines the mask (which bits matter) and expected value (what those btis should be)
+             * into a single 32-bit value that uniquely represents this instruction pattern.
+             * Example: ADD instruction might have mask=0x0FF00000, expected=0x00200000
+             *          value = 0x0FF00000 ^ 0x00200000 = 0x0FD00000;
+             */
+    uint32_t value = mask ^ expected;
 
+    /*
+             * First bit mixing round - break up patterns in the value.
+             * We need to eliminate patterns (like trailing zeroes) that cause collisions.
+             * We do this by mixing the high bits (16-31) with the low bits (0-15).
+             *
+             * We then multiply a magic number to further scrambles the bits to ensure good distribution.
+             */
+    value = ((value >> 16) ^ value) * 0x45d9f3b;
+
+    /*
+             * Second bit mixing round to ensire thorough mixing
+             */
+    value = ((value >> 16) ^ value) * 0x45d9f3b;
+
+    /*
+             * Final mixing. The result is our hash seed - a 32-bit number that uniquely represents this instruction.
+             */
+    value = (value >> 16) ^ value;
+    return value;
+}
 }  // namespace pound::jit::decoder

src/jit/decoder/arm32.h

@@ -13,6 +13,14 @@ typedef uint32_t arm32_instruction_t;
 typedef struct arm32_decoder arm32_decoder_t;
 typedef void (*arm32_handler_fn)(arm32_decoder_t* decoder, arm32_instruction_t instruction);
 
+typedef struct
+{
+    uint16_t* hash_table;
+    uint16_t hash_shift;
+    uint16_t hash_mask;
+    uint16_t table_size;
+} arm32_perfect_hash_t;
+
 typedef struct
 {
     const char* name;
@@ -27,27 +35,15 @@ typedef struct
 
 struct arm32_decoder
 {
+    arm32_perfect_hash_t perfect_hash;
     pound::host::memory::arena_t allocator;
     arm32_instruction_info_t* instructions;
     size_t instruction_count;
     size_t instruction_capacity;
-
-    struct
-    {
-        arm32_instruction_info_t** bucket;
-        size_t count;
-        size_t capacity;
-    } lookup_table[4096]; /* 2^12 entries. */
 };
 
 extern arm32_decoder_t g_arm32_decoder;
 
 void arm32_init(pound::host::memory::arena_t allocator, arm32_decoder_t* decoder);
-
-void arm32_add_instruction(arm32_decoder_t* decoder, const char* name, arm32_opcode_t mask, arm32_opcode_t expected,
-                           arm32_handler_fn handler);
-void arm32_ADD_imm_handler(arm32_decoder_t* decoder, arm32_instruction_t instruction);
-
-
-}  // namespace pound::jit::decoder
-#endif  // POUND_JIT_DECODER_ARM32_H
+}
+#endif  // POUND_JIT_DECODER_ARM32_H

src/jit/decoder/arm32.inc

@@ -64,7 +64,7 @@ INST(ADD_imm, "ADD (imm)", "cccc0010100Snnnnddddrrrrvvvvvvvv")  // v1
 //INST(SBC_imm,       "SBC (imm)",           "cccc0010110Snnnnddddrrrrvvvvvvvv") // v1
 //INST(SBC_reg,       "SBC (reg)",           "cccc0000110Snnnnddddvvvvvrr0mmmm") // v1
 //INST(SBC_rsr,       "SBC (rsr)",           "cccc0000110Snnnnddddssss0rr1mmmm") // v1
-//INST(SUB_imm,       "SUB (imm)",           "cccc0010010Snnnnddddrrrrvvvvvvvv") // v1
+INST(SUB_imm,       "SUB (imm)",           "cccc0010010Snnnnddddrrrrvvvvvvvv") // v1
 //INST(SUB_reg,       "SUB (reg)",           "cccc0000010Snnnnddddvvvvvrr0mmmm") // v1
 //INST(SUB_rsr,       "SUB (rsr)",           "cccc0000010Snnnnddddssss0rr1mmmm") // v1
 //INST(TEQ_imm,       "TEQ (imm)",           "cccc00110011nnnn0000rrrrvvvvvvvv") // v1

src/main.cpp

@@ -20,7 +20,8 @@
 int main()
 {
     pound::host::memory::arena_t arena = pound::host::memory::arena_init(256);
-    pound::jit::decoder::arm32_init(arena, &pound::jit::decoder::g_arm32_decoder);
+    pound::jit::decoder::arm32_decoder_t decoder = {};
+    pound::jit::decoder::arm32_init(arena, &decoder);
 #if 0
     gui::window_t window = {.data = nullptr, .gl_context = nullptr};
     (void)gui::window_init(&window, "Pound Emulator", 640, 480);