apply 2444de11 to 16-bit and 32-bit decoders

these don't need the extra `rex`-supporting index space, so they don't
have it.

1 files changed, 9 insertions, 6 deletions

diff --git a/src/real_mode/mod.rs b/src/real_mode/mod.rs
index 8749ae2..bff00ad 100644
--- a/src/real_mode/mod.rs
+++ b/src/real_mode/mod.rs
@@ -6089,12 +6089,15 @@ fn read_M<
 
 #[inline]
 fn width_to_gp_reg_bank(width: u8) -> RegisterBank {
-    match width {
-        1 => return RegisterBank::B,
-        2 => return RegisterBank::W,
-        4 => return RegisterBank::D,
-        _ => unsafe { unreachable_unchecked(); }
-    }
+    let index = width.trailing_zeros();
+
+    const BANK_LUT: [RegisterBank; 3] = [
+        RegisterBank::B,
+        RegisterBank::W,
+        RegisterBank::D,
+    ];
+
+    *BANK_LUT.get(index as usize).unwrap_or_else(|| unsafe { unreachable_unchecked() })
 }
 
 fn read_0f_opcode(opcode: u8, prefixes: &mut Prefixes) -> OpcodeRecord {