BREAKING(ffi/unstable): always return u64 as bigint (#23981)

The mixed `number | bigint` representation was useful optimization for
pointers. Now, pointers are represented as V8 externals. As part of the
FFI stabilization effort we want to make `bigint` the only
representation for `u64` and `i64`.

BigInt representation performance is almost on par with mixed
representation with the added benefit that its less confusing and users
don't need manual checks and conversions for doing operations on the
value.

```
cpu: AMD Ryzen 5 7530U with Radeon Graphics
runtime: deno 1.43.6+92a8d09 (x86_64-unknown-linux-gnu)

file:///home/divy/gh/ffi/main.ts
benchmark                 time (avg)        iter/s             (min … max)       p75       p99      p995
-------------------------------------------------------------------------- -----------------------------
nop                        4.01 ns/iter 249,533,690.5     (3.97 ns … 10.8 ns) 3.97 ns 4.36 ns 9.03 ns
ret bigint                 7.74 ns/iter 129,127,186.8    (7.72 ns … 10.46 ns) 7.72 ns 8.11 ns 8.82 ns
ret i32                    7.81 ns/iter 128,087,100.5    (7.77 ns … 12.72 ns) 7.78 ns 8.57 ns 9.75 ns
ret bigint (add op)       15.02 ns/iter  66,588,253.2   (14.64 ns … 24.99 ns) 14.76 ns 19.13 ns 19.44 ns
ret i32    (add op)       12.02 ns/iter  83,209,131.8   (11.95 ns … 18.18 ns) 11.98 ns 13.11 ns 14.5 ns
```

5 files changed, 14 insertions, 96 deletions

diff --git a/ext/ffi/00_ffi.js b/ext/ffi/00_ffi.js
index 19d62dfdd..7f39db13e 100644
--- a/ext/ffi/00_ffi.js
+++ b/ext/ffi/00_ffi.js
@@ -46,7 +46,6 @@ const {
   ObjectDefineProperty,
   ObjectHasOwn,
   ObjectPrototypeIsPrototypeOf,
-  Number,
   NumberIsSafeInteger,
   TypedArrayPrototypeGetBuffer,
   TypedArrayPrototypeGetByteLength,
@@ -348,10 +347,6 @@ function isReturnedAsBigInt(type) {
     type === "usize" || type === "isize";
 }
 
-function isI64(type) {
-  return type === "i64" || type === "isize";
-}
-
 function isStruct(type) {
   return typeof type === "object" && type !== null &&
     typeof type.struct === "object";
@@ -562,7 +557,6 @@ class DynamicLibrary {
         const call = this.symbols[symbol];
         const parameters = symbols[symbol].parameters;
         const vi = new Int32Array(2);
-        const vui = new Uint32Array(TypedArrayPrototypeGetBuffer(vi));
         const b = new BigInt64Array(TypedArrayPrototypeGetBuffer(vi));
 
         const params = ArrayPrototypeJoin(
@@ -572,22 +566,13 @@ class DynamicLibrary {
         // Make sure V8 has no excuse to not optimize this function.
         this.symbols[symbol] = new Function(
           "vi",
-          "vui",
           "b",
           "call",
-          "NumberIsSafeInteger",
-          "Number",
           `return function (${params}) {
             call(${params}${parameters.length > 0 ? ", " : ""}vi);
-            ${
-            isI64(resultType)
-              ? `const n1 = Number(b[0])`
-              : `const n1 = vui[0] + 2 ** 32 * vui[1]` // Faster path for u64
-          };
-            if (NumberIsSafeInteger(n1)) return n1;
             return b[0];
           }`,
-        )(vi, vui, b, call, NumberIsSafeInteger, Number);
+        )(vi, b, call);
       } else if (isStructResult && !isNonBlocking) {
         const call = this.symbols[symbol];
         const parameters = symbols[symbol].parameters;
diff --git a/ext/ffi/callback.rs b/ext/ffi/callback.rs
index 55f38c602..1ddb1fff5 100644
--- a/ext/ffi/callback.rs
+++ b/ext/ffi/callback.rs
@@ -4,8 +4,6 @@ use crate::check_unstable;
 use crate::symbol::NativeType;
 use crate::FfiPermissions;
 use crate::ForeignFunction;
-use crate::MAX_SAFE_INTEGER;
-use crate::MIN_SAFE_INTEGER;
 use deno_core::error::AnyError;
 use deno_core::op2;
 use deno_core::v8;
@@ -243,20 +241,11 @@ unsafe fn do_ffi_callback(
       }
       NativeType::I64 | NativeType::ISize => {
         let result = *((*val) as *const i64);
-        if result > MAX_SAFE_INTEGER as i64 || result < MIN_SAFE_INTEGER as i64
-        {
-          v8::BigInt::new_from_i64(scope, result).into()
-        } else {
-          v8::Number::new(scope, result as f64).into()
-        }
+        v8::BigInt::new_from_i64(scope, result).into()
       }
       NativeType::U64 | NativeType::USize => {
         let result = *((*val) as *const u64);
-        if result > MAX_SAFE_INTEGER as u64 {
-          v8::BigInt::new_from_u64(scope, result).into()
-        } else {
-          v8::Number::new(scope, result as f64).into()
-        }
+        v8::BigInt::new_from_u64(scope, result).into()
       }
       NativeType::Pointer | NativeType::Buffer | NativeType::Function => {
         let result = *((*val) as *const *mut c_void);
diff --git a/ext/ffi/ir.rs b/ext/ffi/ir.rs
index 6fd1f53ea..520ead92e 100644
--- a/ext/ffi/ir.rs
+++ b/ext/ffi/ir.rs
@@ -1,8 +1,6 @@
 // Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
 
 use crate::symbol::NativeType;
-use crate::MAX_SAFE_INTEGER;
-use crate::MIN_SAFE_INTEGER;
 use deno_core::error::type_error;
 use deno_core::error::AnyError;
 use deno_core::v8;
@@ -100,46 +98,13 @@ impl NativeValue {
         v8::Integer::new_from_unsigned(scope, self.u32_value).into()
       }
       NativeType::I32 => v8::Integer::new(scope, self.i32_value).into(),
-      NativeType::U64 => {
-        let value = self.u64_value;
-        let local_value: v8::Local<v8::Value> =
-          if value > MAX_SAFE_INTEGER as u64 {
-            v8::BigInt::new_from_u64(scope, value).into()
-          } else {
-            v8::Number::new(scope, value as f64).into()
-          };
-        local_value
-      }
-      NativeType::I64 => {
-        let value = self.i64_value;
-        let local_value: v8::Local<v8::Value> =
-          if value > MAX_SAFE_INTEGER as i64 || value < MIN_SAFE_INTEGER as i64
-          {
-            v8::BigInt::new_from_i64(scope, self.i64_value).into()
-          } else {
-            v8::Number::new(scope, value as f64).into()
-          };
-        local_value
-      }
+      NativeType::U64 => v8::BigInt::new_from_u64(scope, self.u64_value).into(),
+      NativeType::I64 => v8::BigInt::new_from_i64(scope, self.i64_value).into(),
       NativeType::USize => {
-        let value = self.usize_value;
-        let local_value: v8::Local<v8::Value> =
-          if value > MAX_SAFE_INTEGER as usize {
-            v8::BigInt::new_from_u64(scope, value as u64).into()
-          } else {
-            v8::Number::new(scope, value as f64).into()
-          };
-        local_value
+        v8::BigInt::new_from_u64(scope, self.usize_value as u64).into()
       }
       NativeType::ISize => {
-        let value = self.isize_value;
-        let local_value: v8::Local<v8::Value> =
-          if !(MIN_SAFE_INTEGER..=MAX_SAFE_INTEGER).contains(&value) {
-            v8::BigInt::new_from_i64(scope, self.isize_value as i64).into()
-          } else {
-            v8::Number::new(scope, value as f64).into()
-          };
-        local_value
+        v8::BigInt::new_from_i64(scope, self.isize_value as i64).into()
       }
       NativeType::F32 => v8::Number::new(scope, self.f32_value as f64).into(),
       NativeType::F64 => v8::Number::new(scope, self.f64_value).into(),
diff --git a/ext/ffi/lib.rs b/ext/ffi/lib.rs
index c678a10b5..4e8129240 100644
--- a/ext/ffi/lib.rs
+++ b/ext/ffi/lib.rs
@@ -39,9 +39,6 @@ const _: () = {
   assert!(size_of::<*const ()>() == 8);
 };
 
-pub(crate) const MAX_SAFE_INTEGER: isize = 9007199254740991;
-pub(crate) const MIN_SAFE_INTEGER: isize = -9007199254740991;
-
 pub const UNSTABLE_FEATURE_NAME: &str = "ffi";
 
 fn check_unstable(state: &OpState, api_name: &str) {
diff --git a/ext/ffi/static.rs b/ext/ffi/static.rs
index 3920d885e..f08605754 100644
--- a/ext/ffi/static.rs
+++ b/ext/ffi/static.rs
@@ -2,8 +2,6 @@
 
 use crate::dlfcn::DynamicLibraryResource;
 use crate::symbol::NativeType;
-use crate::MAX_SAFE_INTEGER;
-use crate::MIN_SAFE_INTEGER;
 use deno_core::error::type_error;
 use deno_core::error::AnyError;
 use deno_core::op2;
@@ -90,45 +88,29 @@ pub fn op_ffi_get_static<'scope>(
     NativeType::U64 => {
       // SAFETY: ptr is user provided
       let result = unsafe { ptr::read_unaligned(data_ptr as *const u64) };
-      let integer: v8::Local<v8::Value> = if result > MAX_SAFE_INTEGER as u64 {
-        v8::BigInt::new_from_u64(scope, result).into()
-      } else {
-        v8::Number::new(scope, result as f64).into()
-      };
+      let integer: v8::Local<v8::Value> =
+        v8::BigInt::new_from_u64(scope, result).into();
       integer
     }
     NativeType::I64 => {
       // SAFETY: ptr is user provided
       let result = unsafe { ptr::read_unaligned(data_ptr as *const i64) };
-      let integer: v8::Local<v8::Value> = if result > MAX_SAFE_INTEGER as i64
-        || result < MIN_SAFE_INTEGER as i64
-      {
-        v8::BigInt::new_from_i64(scope, result).into()
-      } else {
-        v8::Number::new(scope, result as f64).into()
-      };
+      let integer: v8::Local<v8::Value> =
+        v8::BigInt::new_from_i64(scope, result).into();
       integer
     }
     NativeType::USize => {
       // SAFETY: ptr is user provided
       let result = unsafe { ptr::read_unaligned(data_ptr as *const usize) };
-      let integer: v8::Local<v8::Value> = if result > MAX_SAFE_INTEGER as usize
-      {
-        v8::BigInt::new_from_u64(scope, result as u64).into()
-      } else {
-        v8::Number::new(scope, result as f64).into()
-      };
+      let integer: v8::Local<v8::Value> =
+        v8::BigInt::new_from_u64(scope, result as u64).into();
       integer
     }
     NativeType::ISize => {
       // SAFETY: ptr is user provided
       let result = unsafe { ptr::read_unaligned(data_ptr as *const isize) };
       let integer: v8::Local<v8::Value> =
-        if !(MIN_SAFE_INTEGER..=MAX_SAFE_INTEGER).contains(&result) {
-          v8::BigInt::new_from_i64(scope, result as i64).into()
-        } else {
-          v8::Number::new(scope, result as f64).into()
-        };
+        v8::BigInt::new_from_i64(scope, result as i64).into();
       integer
     }
     NativeType::F32 => {