Remove superseeded conditional branch instructions (#805)

* add TryFrom<BranchOffset> for BranchOffset16

* move From impl

* remove superseeded branch+cmp instructions

* fix intra doc links

* refactor implementation of cmp+br instructions

* apply rustfmt

* reduce column noise

crates/wasmi/src/engine/regmach/bytecode/construct.rs

@@ -224,8 +224,8 @@ macro_rules! constructor_for_branch_binop_imm {
         impl Instruction {
             $(
                 #[doc = concat!("Creates a new [`Instruction::", stringify!($op_code), "`].")]
-                pub fn $name(lhs: Register, rhs: Const16<$ty>, offset: BranchOffset16) -> Self {
-                    Self::$op_code(BranchBinOpInstrImm16::new(lhs, rhs, offset))
+                pub fn $name(lhs: Register, rhs: impl Into<Const16<$ty>>, offset: BranchOffset16) -> Self {
+                    Self::$op_code(BranchBinOpInstrImm16::new(lhs, rhs.into(), offset))
                 }
             )*
         }
@@ -412,24 +412,24 @@ impl Instruction {
         Self::Branch { offset }
     }
 
-    /// Creates a new [`Instruction::BranchI32Eqz`] for the given `condition` and `offset`.
-    pub fn branch_i32_eqz(condition: Register, offset: BranchOffset) -> Self {
-        Self::BranchI32Eqz { condition, offset }
+    /// Convenience constructor to create a new [`Instruction::BranchI32EqImm`] with a zero immediate value.
+    pub fn branch_i32_eqz(condition: Register, offset: BranchOffset16) -> Self {
+        Self::branch_i32_eq_imm(condition, 0_i16, offset)
     }
 
-    /// Creates a new [`Instruction::BranchI32Nez`] for the given `condition` and `offset`.
-    pub fn branch_i32_nez(condition: Register, offset: BranchOffset) -> Self {
-        Self::BranchI32Nez { condition, offset }
+    /// Convenience constructor to create a new [`Instruction::BranchI32NeImm`] with a zero immediate value.
+    pub fn branch_i32_nez(condition: Register, offset: BranchOffset16) -> Self {
+        Self::branch_i32_ne_imm(condition, 0_i16, offset)
     }
 
-    /// Creates a new [`Instruction::BranchI64Eqz`] for the given `condition` and `offset`.
-    pub fn branch_i64_eqz(condition: Register, offset: BranchOffset) -> Self {
-        Self::BranchI64Eqz { condition, offset }
+    /// Convenience constructor to create a new [`Instruction::BranchI64EqImm`] with a zero immediate value.
+    pub fn branch_i64_eqz(condition: Register, offset: BranchOffset16) -> Self {
+        Self::branch_i64_eq_imm(condition, 0_i16, offset)
     }
 
-    /// Creates a new [`Instruction::BranchI64Nez`] for the given `condition` and `offset`.
-    pub fn branch_i64_nez(condition: Register, offset: BranchOffset) -> Self {
-        Self::BranchI64Nez { condition, offset }
+    /// Convenience constructor to create a new [`Instruction::BranchI64NeImm`] with a zero immediate value.
+    pub fn branch_i64_nez(condition: Register, offset: BranchOffset16) -> Self {
+        Self::branch_i64_ne_imm(condition, 0_i16, offset)
     }
 
     /// Creates a new [`Instruction::BranchTable`] for the given `index` and `len_targets`.

crates/wasmi/src/engine/regmach/bytecode/utils.rs

@@ -491,6 +491,25 @@ impl From<i16> for BranchOffset16 {
     }
 }
 
+impl TryFrom<BranchOffset> for BranchOffset16 {
+    type Error = TranslationError;
+
+    fn try_from(offset: BranchOffset) -> Result<Self, Self::Error> {
+        let Ok(offset16) = i16::try_from(offset.to_i32()) else {
+            return Err(TranslationError::new(
+                TranslationErrorInner::BranchOffsetOutOfBounds,
+            ));
+        };
+        Ok(Self(offset16))
+    }
+}
+
+impl From<BranchOffset16> for BranchOffset {
+    fn from(offset: BranchOffset16) -> Self {
+        Self::from(i32::from(offset.to_i16()))
+    }
+}
+
 impl BranchOffset16 {
     /// Creates a 16-bit [`BranchOffset16`] from a 32-bit [`BranchOffset`] if possible.
     pub fn new(offset: BranchOffset) -> Option<Self> {
@@ -527,12 +546,6 @@ impl BranchOffset16 {
     }
 }
 
-impl From<BranchOffset16> for BranchOffset {
-    fn from(offset: BranchOffset16) -> Self {
-        Self::from(i32::from(offset.to_i16()))
-    }
-}
-
 /// A generic fused comparison and conditional branch [`Instruction`].
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 pub struct BranchBinOpInstr {

crates/wasmi/src/engine/regmach/executor/instrs.rs

@@ -245,18 +245,6 @@ impl<'ctx, 'engine> Executor<'ctx, 'engine> {
                     forward_return!(self.execute_return_nez_many(condition, values))
                 }
                 Instr::Branch { offset } => self.execute_branch(offset),
-                Instr::BranchI32Eqz { condition, offset } => {
-                    self.execute_branch_i32_eqz(condition, offset)
-                }
-                Instr::BranchI32Nez { condition, offset } => {
-                    self.execute_branch_i32_nez(condition, offset)
-                }
-                Instr::BranchI64Eqz { condition, offset } => {
-                    self.execute_branch_i64_eqz(condition, offset)
-                }
-                Instr::BranchI64Nez { condition, offset } => {
-                    self.execute_branch_i64_nez(condition, offset)
-                }
                 Instr::BranchTable { index, len_targets } => {
                     self.execute_branch_table(index, len_targets)
                 }