Fix LOADU8 (#156)

* Fix LOADU8 It was generating wrong results * Remove zero_extend_byte and update sign_extend_byte. --------- Co-authored-by: Hasekawa-Takumi <[email protected]> Co-authored-by: thealmarty <“[email protected]”>
valida-xyz · Apr 22, 2024 · 1f8d3d9 · 1f8d3d9
1 parent f8c192d
commit 1f8d3d9
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Showing 2 changed files with 3 additions and 13 deletions.
diff --git a/cpu/src/lib.rs b/cpu/src/lib.rs
@@ -514,18 +514,16 @@ where
         // The array index of the word for the byte to read from
         let index_of_read = index_of_byte(read_addr.into());
         // The byte from the read cell.
-        let cell_byte = cell[index_of_read];
+        let cell_byte: u8 = cell[index_of_read];
 
         let write_addr = (state.cpu().fp as i32 + ops.a()) as u32;
         // The address, converted to a multiple of 4.
         let write_addr_index = addr_of_word(write_addr);
 
         // The Word to write, with one byte overwritten to the read byte
-        let cell_to_write = Word::zero_extend_byte(cell_byte);
-
         state
             .mem_mut()
-            .write(clk, write_addr_index, cell_to_write, true);
+            .write(clk, write_addr_index, Word::from_u8(cell_byte), true);
         state.cpu_mut().pc += 1;
         state.cpu_mut().push_op(Operation::LoadU8, opcode, ops);
     }

diff --git a/machine/src/core.rs b/machine/src/core.rs
@@ -35,15 +35,7 @@ impl Word<u8> {
     pub fn sign_extend_byte(byte: u8) -> Self {
         let sign = byte as i8 >> 7;
         let mut result: [u8; MEMORY_CELL_BYTES] = [sign as u8; MEMORY_CELL_BYTES];
-        result[0] = byte;
-        Self(result)
-    }
-}
-
-impl Word<u8> {
-    pub fn zero_extend_byte(byte: u8) -> Self {
-        let mut result: [u8; MEMORY_CELL_BYTES] = [0; MEMORY_CELL_BYTES];
-        result[0] = byte;
+        result[3] = byte;
         Self(result)
     }
 }