engine: add constants array

This was tricky one to add to bal_engine_t because the struct was
already pretty packed. The struct only had 12 bytes to spare but to add
the constants array and its size required 16 bytes. I determined that
ssa_bit_widths_size was not required since ssa_bit_widths[] and
instructions[] will be parallel to each other, so one variable can keep
track of both arrays.

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

include/bal_engine.h

@@ -46,7 +46,8 @@ BAL_ALIGNED(64) typedef struct
     bal_source_variable_t *source_variables;
 
     /*!
-     * @brief The linear buffer of generated IR instructions.
+     * @brief The linear buffer of generated IR instructions in a compilation
+     * unit.
      */
     bal_instruction_t *instructions;
 
@@ -55,6 +56,11 @@ BAL_ALIGNED(64) typedef struct
      */
     bal_bit_width_t *ssa_bit_widths;
 
+    /*!
+     * @brief Linear buffer of constants generated in a compilation unit.
+     */
+    bal_constant_t *constants;
+
     /*!
      * @brief Size of source variable array.
      */
@@ -66,22 +72,29 @@ BAL_ALIGNED(64) typedef struct
     size_t instructions_size;
 
     /*!
-     * @brief Size of ssa bit width array.
+     * @brief Size of the constants array.
      */
-    size_t ssa_bit_widths_size;
+    size_t constants_size;
 
     /*!
      * @brief The current number of instructions emitted.
+     *
+     * @detials
+     * This keeps track of where we are in the instruction and ssa bit width
+     * arrays to make sure we dont cause an instruction overflow.
      */
     bal_instruction_count_t instruction_count;
 
+    char _padding[2];
+
     /*!
-     * @brief The Engine's error state.
+     * @brief The Engine's state.
-     * @details If an operation fails, this is set to a specific error code.
+     *
+     * @details
+     * If an operation fails, this is set to a specific error code.
      * Subsequent operations will silently fail until the engine is reset.
      */
     bal_error_t status;
-    char        _pad[4];
 
     /* Cold Data */
 

include/bal_types.h

@@ -11,6 +11,7 @@
 
 typedef uint64_t bal_guest_address_t;
 typedef uint32_t bal_instruction_t;
+typedef uint32_t bal_constant_t;
 typedef uint16_t bal_instruction_count_t;
 typedef uint16_t bal_ssa_id_t;
 typedef uint8_t  bal_bit_width_t;

src/bal_engine.c

@@ -26,6 +26,7 @@ bal_engine_init (bal_allocator_t *allocator, bal_engine_t *engine)
 
     size_t ssa_bit_widths_size = MAX_INSTRUCTIONS * sizeof(bal_bit_width_t);
     size_t instructions_size   = MAX_INSTRUCTIONS * sizeof(bal_instruction_t);
+    size_t constants_size      = MAX_INSTRUCTIONS * sizeof(bal_instruction_t);
 
     // Calculate amount of memory needed for all arrays in engine.
     //
@@ -37,9 +38,12 @@ bal_engine_init (bal_allocator_t *allocator, bal_engine_t *engine)
     size_t offset_ssa_bit_widths = BAL_ALIGN_UP(
         (offset_instructions + instructions_size), memory_alignment);
 
-    size_t total_size_with_padding = BAL_ALIGN_UP(
+    size_t offset_constants = BAL_ALIGN_UP(
         (offset_ssa_bit_widths + ssa_bit_widths_size), memory_alignment);
 
+    size_t total_size_with_padding
+        = BAL_ALIGN_UP((offset_constants + constants_size), memory_alignment);
+
     uint8_t *data = (uint8_t *)allocator->allocate(
         allocator, memory_alignment, total_size_with_padding);
 
@@ -52,9 +56,10 @@ bal_engine_init (bal_allocator_t *allocator, bal_engine_t *engine)
     engine->source_variables = (bal_source_variable_t *)data;
     engine->instructions   = (bal_instruction_t *)(data + offset_instructions);
     engine->ssa_bit_widths = (bal_bit_width_t *)(data + offset_ssa_bit_widths);
+    engine->constants      = (bal_constant_t *)(data + offset_constants);
     engine->source_variables_size = source_variables_size;
     engine->instructions_size     = instructions_size;
-    engine->ssa_bit_widths_size   = ssa_bit_widths_size;
+    engine->constants_size        = constants_size;
     engine->instruction_count     = 0;
     engine->status                = BAL_SUCCESS;
     engine->arena_base            = (void *)data;
@@ -71,6 +76,9 @@ bal_engine_init (bal_allocator_t *allocator, bal_engine_t *engine)
                  POISON_UNINITIALIZED_MEMORY,
                  ssa_bit_widths_size);
 
+    (void)memset(
+        engine->constants, POISON_UNINITIALIZED_MEMORY, constants_size);
+
     return engine->status;
 }
 
@@ -79,7 +87,7 @@ bal_engine_translate (bal_engine_t *BAL_RESTRICT           engine,
                       bal_memory_interface_t *BAL_RESTRICT interface,
                       const uint32_t *BAL_RESTRICT         arm_entry_point)
 {
-    if (NULL == engine || NULL == arm_entry_point)
+    if (BAL_UNLIKELY(NULL == engine || NULL == arm_entry_point))
     {
         return BAL_ERROR_ENGINE_STATE_INVALID;
     }
@@ -121,12 +129,12 @@ bal_engine_reset (bal_engine_t *engine)
     engine->instruction_count = 0;
     engine->status            = BAL_SUCCESS;
 
-    size_t source_variables_size
-        = MAX_GUEST_REGISTERS * sizeof(bal_source_variable_t);
-
     (void)memset(engine->source_variables,
                  POISON_UNINITIALIZED_MEMORY,
-                 source_variables_size);
+                 engine->source_variables_size);
+
+    (void)memset(
+        engine->constants, POISON_UNINITIALIZED_MEMORY, engine->constants_size);
 
     return engine->status;
 }