From c8026715f05eb7a86178a31d1b63c5cb3d998804 Mon Sep 17 00:00:00 2001
From: Luke Street <luke@street.dev>
Date: Thu, 26 Sep 2024 23:18:47 -0600
Subject: [PATCH] impl From<u8> for Opcode

---
 disasm/src/generated.rs | 19 ++++++++++++++++++-
 genisa/src/disasm.rs    | 21 ++++++++++++++++++++-
 2 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/disasm/src/generated.rs b/disasm/src/generated.rs
index bf71a48..5fab65e 100644
--- a/disasm/src/generated.rs
+++ b/disasm/src/generated.rs
@@ -1051,13 +1051,30 @@ impl Opcode {
         for i in entry.0..entry.1 {
             let pattern = OPCODE_PATTERNS[i as usize];
             if (code & pattern.0) == pattern.1 {
-                // Safety: The enum is repr(u8) and marked non_exhaustive
+                // Safety: The enum is repr(u8) and the value is within the enum's range
                 return unsafe { core::mem::transmute::<u8, Opcode>(i) };
             }
         }
         Self::Illegal
     }
 }
+impl From<u8> for Opcode {
+    #[inline]
+    fn from(value: u8) -> Self {
+        if value > 221 {
+            Self::Illegal
+        } else {
+            // Safety: The enum is repr(u8) and the value is within the enum's range
+            unsafe { core::mem::transmute::<u8, Self>(value) }
+        }
+    }
+}
+impl From<Opcode> for u8 {
+    #[inline]
+    fn from(value: Opcode) -> Self {
+        value as u8
+    }
+}
 impl Ins {
     /// simm: Signed Immediate
     #[inline(always)]
diff --git a/genisa/src/disasm.rs b/genisa/src/disasm.rs
index f131e8a..514defd 100644
--- a/genisa/src/disasm.rs
+++ b/genisa/src/disasm.rs
@@ -41,6 +41,8 @@ pub fn gen_disasm(isa: &Isa, max_args: usize) -> Result<TokenStream> {
         entries.push(entry);
     }
     ensure!(sorted_ops.len() == isa.opcodes.len());
+    ensure!(sorted_ops.len() <= 256);
+    let opcode_max = Literal::u8_unsuffixed((sorted_ops.len() - 1) as u8);
 
     // Generate the opcode entries table
     let mut opcode_entries = TokenStream::new();
@@ -337,13 +339,30 @@ pub fn gen_disasm(isa: &Isa, max_args: usize) -> Result<TokenStream> {
                 for i in entry.0..entry.1 {
                     let pattern = OPCODE_PATTERNS[i as usize];
                     if (code & pattern.0) == pattern.1 {
-                        #[comment = " Safety: The enum is repr(u8) and marked non_exhaustive"]
+                        #[comment = " Safety: The enum is repr(u8) and the value is within the enum's range"]
                         return unsafe { core::mem::transmute::<u8, Opcode>(i) };
                     }
                 }
                 Self::Illegal
             }
         }
+        impl From<u8> for Opcode {
+            #[inline]
+            fn from(value: u8) -> Self {
+                if value > #opcode_max {
+                    Self::Illegal
+                } else {
+                    #[comment = " Safety: The enum is repr(u8) and the value is within the enum's range"]
+                    unsafe { core::mem::transmute::<u8, Self>(value) }
+                }
+            }
+        }
+        impl From<Opcode> for u8 {
+            #[inline]
+            fn from(value: Opcode) -> Self {
+                value as u8
+            }
+        }
 
         impl Ins {
             #ins_fields