implement block.number and block.timestamp

Signed-off-by: xermicus <cyrill@parity.io>

crates/llvm-context/src/polkavm/const/mod.rs

@@ -43,7 +43,13 @@ pub static GLOBAL_CONST_ARRAY_PREFIX: &str = "const_array_";
 pub static GLOBAL_VERBATIM_GETTER_PREFIX: &str = "get_global::";
 
 /// The static word size.
-pub static GLOBAL_WORD_SIZE: &str = "word_size";
+pub static GLOBAL_I256_SIZE: &str = "i256_size";
+
+/// The static value size.
+pub static GLOBAL_I128_SIZE: &str = "i128_size";
+
+/// The static i64 size.
+pub static GLOBAL_I64_SIZE: &str = "i64_size";
 
 /// The external call data offset in the auxiliary heap.
 pub const HEAP_AUX_OFFSET_EXTERNAL_CALL: u64 = 0;

crates/llvm-context/src/polkavm/const/runtime_api.rs

@@ -10,12 +10,16 @@ pub static DEPLOY: &str = "deploy";
 /// Useful for configuring common attributes and linkage.
 pub static EXPORTS: [&str; 2] = [CALL, DEPLOY];
 
+pub static BLOCK_NUMBER: &str = "block_number";
+
 pub static GET_STORAGE: &str = "get_storage";
 
 pub static HASH_KECCAK_256: &str = "hash_keccak_256";
 
 pub static INPUT: &str = "input";
 
+pub static NOW: &str = "now";
+
 pub static RETURN: &str = "seal_return";
 
 pub static SET_STORAGE: &str = "set_storage";