give immediates a sign & fix stuff

src/arch/x86_64/reg.rs

@@ -52,8 +52,10 @@ impl Reg {
     }
 
     /// if self has 64 bit width, changes width to 32 bit
-    pub fn lower64(&mut self) {
-        self.width.lower64()
+    pub fn lower64(&self) -> Self {
+        let mut new = *self;
+        new.width = new.width.min(Width::B32);
+        new
     }
 
     pub fn requires_rex(&self) -> bool {
@@ -76,7 +78,7 @@ impl Reg {
 }
 
 impl Width {
-    pub const fn max(&self) -> u64 {
+    pub const fn max_val(&self) -> u64 {
         match self {
             Self::B64 => u64::MAX,
             Self::B32 => u32::MAX as u64,
@@ -85,10 +87,8 @@ impl Width {
         }
     }
 
-    pub fn lower64(&mut self) {
-        if matches!(self, Width::B64) {
-            *self = Width::B32;
-        }
+    pub fn min(self, other: Self) -> Self {
+        if self <= other { self } else { other }
     }
 
     pub const fn bytes(&self) -> usize {
@@ -100,27 +100,6 @@ impl Width {
         }
     }
 
-    pub const fn fit(val: u64) -> Self {
-        const B8: u64 = 1 << 8;
-        const B16: u64 = 1 << 16;
-        const B32: u64 = 1 << 32;
-        match val {
-            ..B8 => Self::B8,
-            B8..B16 => Self::B16,
-            B16..B32 => Self::B32,
-            B32.. => Self::B64,
-        }
-    }
-
-    pub const fn fiti(val: u64) -> Self {
-        match val {
-            ..0x80 => Self::B8,
-            0x80..0x8000 => Self::B16,
-            0x8000..0x8000_0000 => Self::B32,
-            0x8000_0000.. => Self::B64,
-        }
-    }
-
     /// greater than 8 bits
     pub const fn gt8(&self) -> bool {
         !matches!(self, Self::B8)
@@ -205,6 +184,8 @@ macro_rules! def_regs {
 
 use def_regs;
 
+use crate::arch::x86_64::Imm;
+
 impl From<Reg> for Width {
     fn from(value: Reg) -> Self {
         value.width