diff --git a/crates/compiler/builtins/bitcode/src/dec.zig b/crates/compiler/builtins/bitcode/src/dec.zig
index e2be7dbe56..e74e361074 100644
--- a/crates/compiler/builtins/bitcode/src/dec.zig
+++ b/crates/compiler/builtins/bitcode/src/dec.zig
@@ -1125,6 +1125,23 @@ pub fn fromF64C(arg: f64) callconv(.C) i128 {
     return if (@call(.{ .modifier = always_inline }, RocDec.fromF64, .{arg})) |dec| dec.num else @panic("TODO runtime exception failing convert f64 to RocDec");
 }
 
+pub fn exportFromInt(comptime T: type, comptime name: []const u8) void {
+    comptime var f = struct {
+        fn func(self: T) callconv(.C) i128 {
+            const this = @intCast(i128, self);
+
+            var result: i128 = undefined;
+
+            if (@mulWithOverflow(i128, this, RocDec.one_point_zero_i128, &result)) {
+                @panic("TODO runtime exception failing convert integer to RocDec");
+            } else {
+                return result;
+            }
+        }
+    }.func;
+    @export(f, .{ .name = name ++ @typeName(T), .linkage = .Strong });
+}
+
 pub fn fromU64C(arg: u64) callconv(.C) i128 {
     return @call(.{ .modifier = always_inline }, RocDec.fromU64, .{arg}).toI128();
 }
diff --git a/crates/compiler/builtins/bitcode/src/main.zig b/crates/compiler/builtins/bitcode/src/main.zig
index 4d3b8a342e..a93e60314e 100644
--- a/crates/compiler/builtins/bitcode/src/main.zig
+++ b/crates/compiler/builtins/bitcode/src/main.zig
@@ -39,6 +39,10 @@ comptime {
     exportDecFn(dec.mulC, "mul_with_overflow");
     exportDecFn(dec.mulOrPanicC, "mul_or_panic");
     exportDecFn(dec.mulSaturatedC, "mul_saturated");
+
+    inline for (INTEGERS) |T| {
+        dec.exportFromInt(T, ROC_BUILTINS ++ ".dec.from_int.");
+    }
 }
 
 // List Module
diff --git a/crates/compiler/builtins/src/bitcode.rs b/crates/compiler/builtins/src/bitcode.rs
index ca356053e6..a0cf671d33 100644
--- a/crates/compiler/builtins/src/bitcode.rs
+++ b/crates/compiler/builtins/src/bitcode.rs
@@ -390,6 +390,7 @@ pub const DEC_FROM_STR: &str = "roc_builtins.dec.from_str";
 pub const DEC_TO_STR: &str = "roc_builtins.dec.to_str";
 pub const DEC_FROM_F64: &str = "roc_builtins.dec.from_f64";
 pub const DEC_FROM_U64: &str = "roc_builtins.dec.from_u64";
+pub const DEC_FROM_INT: IntrinsicName = int_intrinsic!("roc_builtins.dec.from_int");
 pub const DEC_TO_I128: &str = "roc_builtins.dec.to_i128";
 pub const DEC_EQ: &str = "roc_builtins.dec.eq";
 pub const DEC_NEQ: &str = "roc_builtins.dec.neq";
diff --git a/crates/compiler/gen_dev/src/generic64/mod.rs b/crates/compiler/gen_dev/src/generic64/mod.rs
index 918302e383..607a41b02c 100644
--- a/crates/compiler/gen_dev/src/generic64/mod.rs
+++ b/crates/compiler/gen_dev/src/generic64/mod.rs
@@ -1560,7 +1560,7 @@ impl<
                     .load_to_general_reg(&mut self.buf, src2);
                 ASM::eq_reg_reg_reg(&mut self.buf, width, dst_reg, src1_reg, src2_reg);
             }
-            LayoutRepr::U128 | LayoutRepr::I128 => {
+            LayoutRepr::U128 | LayoutRepr::I128 | LayoutRepr::DEC => {
                 let dst_reg = self.storage_manager.claim_general_reg(&mut self.buf, dst);
 
                 // put the arguments on the stack
@@ -1611,7 +1611,6 @@ impl<
 
                 ASM::eq_freg_freg_reg64(&mut self.buf, dst_reg, src_reg1, src_reg2, float_width)
             }
-            LayoutRepr::DEC => todo!("NumEq: layout, {:?}", self.layout_interner.dbg(Layout::DEC)),
             LayoutRepr::STR => {
                 // use a zig call
                 self.build_fn_call(
@@ -1753,54 +1752,12 @@ impl<
         arg_layout: &InLayout<'a>,
         ret_layout: &InLayout<'a>,
     ) {
-        let dst_reg = self.storage_manager.claim_float_reg(&mut self.buf, dst);
-        match (
-            self.layout_interner.get_repr(*arg_layout),
-            self.layout_interner.get_repr(*ret_layout),
-        ) {
-            (
-                LayoutRepr::Builtin(Builtin::Int(IntWidth::I32 | IntWidth::I64)),
-                LayoutRepr::Builtin(Builtin::Float(FloatWidth::F64)),
-            ) => {
-                let src_reg = self.storage_manager.load_to_general_reg(&mut self.buf, src);
-                ASM::to_float_freg64_reg64(&mut self.buf, dst_reg, src_reg);
-            }
-            (
-                LayoutRepr::Builtin(Builtin::Int(IntWidth::I32 | IntWidth::I64)),
-                LayoutRepr::Builtin(Builtin::Float(FloatWidth::F32)),
-            ) => {
-                let src_reg = self.storage_manager.load_to_general_reg(&mut self.buf, src);
-                ASM::to_float_freg32_reg64(&mut self.buf, dst_reg, src_reg);
-            }
-            (
-                LayoutRepr::Builtin(Builtin::Float(FloatWidth::F64)),
-                LayoutRepr::Builtin(Builtin::Float(FloatWidth::F32)),
-            ) => {
-                let src_reg = self.storage_manager.load_to_float_reg(&mut self.buf, src);
-                ASM::to_float_freg32_freg64(&mut self.buf, dst_reg, src_reg);
-            }
-            (
-                LayoutRepr::Builtin(Builtin::Float(FloatWidth::F32)),
-                LayoutRepr::Builtin(Builtin::Float(FloatWidth::F64)),
-            ) => {
-                let src_reg = self.storage_manager.load_to_float_reg(&mut self.buf, src);
-                ASM::to_float_freg64_freg32(&mut self.buf, dst_reg, src_reg);
-            }
-            (
-                LayoutRepr::Builtin(Builtin::Float(FloatWidth::F64)),
-                LayoutRepr::Builtin(Builtin::Float(FloatWidth::F64)),
-            ) => {
-                let src_reg = self.storage_manager.load_to_float_reg(&mut self.buf, src);
-                ASM::mov_freg64_freg64(&mut self.buf, dst_reg, src_reg);
-            }
-            (
-                LayoutRepr::Builtin(Builtin::Float(FloatWidth::F32)),
-                LayoutRepr::Builtin(Builtin::Float(FloatWidth::F32)),
-            ) => {
-                let src_reg = self.storage_manager.load_to_float_reg(&mut self.buf, src);
-                ASM::mov_freg64_freg64(&mut self.buf, dst_reg, src_reg);
-            }
-            (a, r) => todo!("NumToFrac: layout, arg {:?}, ret {:?}", a, r),
+        match *ret_layout {
+            Layout::F32 => self.num_to_f32(dst, src, arg_layout),
+            Layout::F64 => self.num_to_f64(dst, src, arg_layout),
+            Layout::DEC => self.num_to_dec(dst, src, arg_layout),
+
+            other => todo!("NumToFrac: layout {other:?} is not Frac"),
         }
     }
 
@@ -4048,6 +4005,84 @@ impl<
         (unmasked_symbol, unmasked_reg)
     }
 
+    fn num_to_f32(&mut self, dst: &Symbol, src: &Symbol, arg_layout: &InLayout<'a>) {
+        let dst_reg = self.storage_manager.claim_float_reg(&mut self.buf, dst);
+        match self.layout_interner.get_repr(*arg_layout) {
+            LayoutRepr::Builtin(Builtin::Int(IntWidth::I32 | IntWidth::I64)) => {
+                let src_reg = self.storage_manager.load_to_general_reg(&mut self.buf, src);
+                ASM::to_float_freg32_reg64(&mut self.buf, dst_reg, src_reg);
+            }
+            LayoutRepr::Builtin(Builtin::Float(FloatWidth::F64)) => {
+                let src_reg = self.storage_manager.load_to_float_reg(&mut self.buf, src);
+                ASM::to_float_freg32_freg64(&mut self.buf, dst_reg, src_reg);
+            }
+            LayoutRepr::Builtin(Builtin::Float(FloatWidth::F32)) => {
+                let src_reg = self.storage_manager.load_to_float_reg(&mut self.buf, src);
+                ASM::mov_freg64_freg64(&mut self.buf, dst_reg, src_reg);
+            }
+            arg => todo!("NumToFrac: layout, arg {arg:?}, ret {:?}", Layout::F32),
+        }
+    }
+
+    fn num_to_f64(&mut self, dst: &Symbol, src: &Symbol, arg_layout: &InLayout<'a>) {
+        let dst_reg = self.storage_manager.claim_float_reg(&mut self.buf, dst);
+        match self.layout_interner.get_repr(*arg_layout) {
+            LayoutRepr::Builtin(Builtin::Int(IntWidth::I32 | IntWidth::I64)) => {
+                let src_reg = self.storage_manager.load_to_general_reg(&mut self.buf, src);
+                ASM::to_float_freg64_reg64(&mut self.buf, dst_reg, src_reg);
+            }
+            LayoutRepr::Builtin(Builtin::Float(FloatWidth::F32)) => {
+                let src_reg = self.storage_manager.load_to_float_reg(&mut self.buf, src);
+                ASM::to_float_freg64_freg32(&mut self.buf, dst_reg, src_reg);
+            }
+            LayoutRepr::Builtin(Builtin::Float(FloatWidth::F64)) => {
+                let src_reg = self.storage_manager.load_to_float_reg(&mut self.buf, src);
+                ASM::mov_freg64_freg64(&mut self.buf, dst_reg, src_reg);
+            }
+            arg => todo!("NumToFrac: layout, arg {arg:?}, ret {:?}", Layout::F64),
+        }
+    }
+
+    fn num_to_dec(&mut self, dst: &Symbol, src: &Symbol, arg_layout: &InLayout<'a>) {
+        match self.layout_interner.get_repr(*arg_layout) {
+            LayoutRepr::Builtin(Builtin::Int(int_width)) => {
+                self.build_fn_call(
+                    dst,
+                    bitcode::DEC_FROM_INT[int_width].to_string(),
+                    &[*src],
+                    &[*arg_layout],
+                    &Layout::DEC,
+                );
+            }
+
+            arg => todo!("NumToFrac: layout, arg {arg:?}, ret {:?}", Layout::DEC),
+        }
+    }
+
+    fn compare_128bit(
+        &mut self,
+        op: CompareOperation,
+        dst: &Symbol,
+        src1: &Symbol,
+        src2: &Symbol,
+        width: IntWidth,
+    ) {
+        let intrinsic = match op {
+            CompareOperation::LessThan => &bitcode::NUM_LESS_THAN[width],
+            CompareOperation::LessThanOrEqual => &bitcode::NUM_LESS_THAN_OR_EQUAL[width],
+            CompareOperation::GreaterThan => &bitcode::NUM_GREATER_THAN[width],
+            CompareOperation::GreaterThanOrEqual => &bitcode::NUM_GREATER_THAN_OR_EQUAL[width],
+        };
+
+        self.build_fn_call(
+            &dst,
+            intrinsic.to_string(),
+            &[*src1, *src2],
+            &[Layout::U128, Layout::U128],
+            &Layout::U8,
+        );
+    }
+
     fn compare(
         &mut self,
         op: CompareOperation,
@@ -4099,6 +4134,12 @@ impl<
                     op,
                 );
             }
+            LayoutRepr::Builtin(Builtin::Int(width @ (IntWidth::I128 | IntWidth::U128))) => {
+                self.compare_128bit(op, dst, src1, src2, width);
+            }
+            LayoutRepr::Builtin(Builtin::Decimal) => {
+                self.compare_128bit(op, dst, src1, src2, IntWidth::I128);
+            }
             x => todo!("NumLt: layout, {:?}", x),
         }
     }
diff --git a/crates/compiler/gen_dev/src/generic64/x86_64.rs b/crates/compiler/gen_dev/src/generic64/x86_64.rs
index a5d969f1d7..cc99cfe8bb 100644
--- a/crates/compiler/gen_dev/src/generic64/x86_64.rs
+++ b/crates/compiler/gen_dev/src/generic64/x86_64.rs
@@ -681,7 +681,7 @@ impl X64_64SystemVStoreArgs {
             single_register_integers!() => self.store_arg_general(buf, storage_manager, sym),
             pointer_layouts!() => self.store_arg_general(buf, storage_manager, sym),
             single_register_floats!() => self.store_arg_float(buf, storage_manager, sym),
-            LayoutRepr::I128 | LayoutRepr::U128 => {
+            LayoutRepr::I128 | LayoutRepr::U128 | LayoutRepr::DEC => {
                 let (offset, _) = storage_manager.stack_offset_and_size(&sym);
 
                 if self.general_i + 1 < Self::GENERAL_PARAM_REGS.len() {
@@ -1004,6 +1004,10 @@ impl X64_64SystemVLoadArgs {
                 storage_manager.complex_stack_arg(&sym, self.argument_offset, stack_size);
                 self.argument_offset += stack_size as i32;
             }
+            LayoutRepr::Builtin(Builtin::Decimal) => {
+                storage_manager.complex_stack_arg(&sym, self.argument_offset, stack_size);
+                self.argument_offset += stack_size as i32;
+            }
             LayoutRepr::Union(UnionLayout::NonRecursive(_)) => {
                 // for now, just also store this on the stack
                 storage_manager.complex_stack_arg(&sym, self.argument_offset, stack_size);
diff --git a/crates/compiler/gen_dev/src/lib.rs b/crates/compiler/gen_dev/src/lib.rs
index efd734864f..b6e8845793 100644
--- a/crates/compiler/gen_dev/src/lib.rs
+++ b/crates/compiler/gen_dev/src/lib.rs
@@ -1255,7 +1255,7 @@ trait Backend<'a> {
                 );
 
                 debug_assert!(
-                    matches!(*ret_layout, Layout::F32 | Layout::F64),
+                    matches!(*ret_layout, Layout::F32 | Layout::F64 | Layout::DEC),
                     "NumToFrac: expected to have return layout of type Float"
                 );
                 self.build_num_to_frac(sym, &args[0], &arg_layouts[0], ret_layout)
diff --git a/crates/compiler/gen_llvm/src/llvm/lowlevel.rs b/crates/compiler/gen_llvm/src/llvm/lowlevel.rs
index 3d13f4c439..34b4656f35 100644
--- a/crates/compiler/gen_llvm/src/llvm/lowlevel.rs
+++ b/crates/compiler/gen_llvm/src/llvm/lowlevel.rs
@@ -2237,7 +2237,7 @@ fn build_int_unary_op<'a, 'ctx, 'env>(
                     )
                 }
                 LayoutRepr::Builtin(Builtin::Decimal) => {
-                    call_bitcode_fn(env, &[arg.into()], &bitcode::DEC_FROM_U64)
+                    call_bitcode_fn(env, &[arg.into()], &bitcode::DEC_FROM_INT[arg_width])
                 }
                 _ => internal_error!("There can only be floats here!"),
             }