speedup sysvar or builtin test (#25047)

* Add a quick lookup table to speed up sysvar/builtin key check

* Fix up the syntax

* Fix syntax

* Fix syntax 2

* Rename the static variable, improve commenting

* Fix merge error

* Fixed two clippy suggestions

* Improved commenting

sdk/program/src/message/legacy.rs

@@ -44,6 +44,27 @@ lazy_static! {
     };
 }
 
+lazy_static! {
+    // Each element of a key is a u8. We use key[0] as an index into this table of 256 boolean
+    // elements, to store whether or not the first element of any key is present in the static
+    // lists of built-in-program keys or system ids. By using this lookup table, we can very
+    // quickly determine that a key under consideration cannot be in either of these lists (if
+    // the value is "false"), or might be in one of these lists (if the value is "true")
+    pub static ref MAYBE_BUILTIN_KEY_OR_SYSVAR: [bool; 256] = {
+        let mut temp_table: [bool; 256] = [false; 256];
+        BUILTIN_PROGRAMS_KEYS.iter().for_each(|key| temp_table[key.0[0] as usize] = true);
+        sysvar::ALL_IDS.iter().for_each(|key| temp_table[key.0[0] as usize] = true);
+        temp_table
+    };
+}
+
+pub fn is_builtin_key_or_sysvar(key: &Pubkey) -> bool {
+    if MAYBE_BUILTIN_KEY_OR_SYSVAR[key.0[0] as usize] {
+        return sysvar::is_sysvar_id(key) || BUILTIN_PROGRAMS_KEYS.contains(key);
+    }
+    false
+}
+
 fn position(keys: &[Pubkey], key: &Pubkey) -> u8 {
     keys.iter().position(|k| k == key).unwrap() as u8
 }
@@ -530,10 +551,7 @@ impl Message {
             || (i >= self.header.num_required_signatures as usize
                 && i < self.account_keys.len()
                     - self.header.num_readonly_unsigned_accounts as usize))
-            && !{
-                let key = self.account_keys[i];
-                sysvar::is_sysvar_id(&key) || BUILTIN_PROGRAMS_KEYS.contains(&key)
-            }
+            && !is_builtin_key_or_sysvar(&self.account_keys[i])
             && !self.demote_program_id(i)
     }
 

sdk/program/src/message/versions/v0/loaded.rs

@@ -1,9 +1,8 @@
 use {
     crate::{
         bpf_loader_upgradeable,
-        message::{legacy::BUILTIN_PROGRAMS_KEYS, v0, AccountKeys},
+        message::{legacy::is_builtin_key_or_sysvar, v0, AccountKeys},
         pubkey::Pubkey,
-        sysvar,
     },
     std::{borrow::Cow, collections::HashSet},
 };
@@ -109,9 +108,7 @@ impl<'a> LoadedMessage<'a> {
     pub fn is_writable(&self, key_index: usize) -> bool {
         if self.is_writable_index(key_index) {
             if let Some(key) = self.account_keys().get(key_index) {
-                return !(sysvar::is_sysvar_id(key)
-                    || BUILTIN_PROGRAMS_KEYS.contains(key)
-                    || self.demote_program_id(key_index));
+                return !(is_builtin_key_or_sysvar(key) || self.demote_program_id(key_index));
             }
         }
         false

sdk/program/src/message/versions/v0/mod.rs

@@ -15,12 +15,12 @@ use crate::{
     hash::Hash,
     instruction::{CompiledInstruction, Instruction},
     message::{
-        compiled_keys::CompileError, legacy::BUILTIN_PROGRAMS_KEYS, AccountKeys, CompiledKeys,
+        compiled_keys::CompileError, legacy::is_builtin_key_or_sysvar, AccountKeys, CompiledKeys,
         MessageHeader, MESSAGE_VERSION_PREFIX,
     },
     pubkey::Pubkey,
     sanitize::SanitizeError,
-    short_vec, sysvar,
+    short_vec,
 };
 pub use loaded::*;
 
@@ -344,7 +344,7 @@ impl Message {
                 // demote reserved ids
                 self.account_keys
                     .get(key_index)
-                    .map(|key| sysvar::is_sysvar_id(key) || BUILTIN_PROGRAMS_KEYS.contains(key))
+                    .map(is_builtin_key_or_sysvar)
                     .unwrap_or_default()
             }
             && !{