unchecked_mul and unchecked_shr proofs (#7)

* Added harnesses for unchecked multiplication (`unchecked_mul`) and shift right (`unchecked_shr`)
* Added a macro and input limits for multiplication proofs
* Reduced duplicity in code by using macros to generate proof harnesses

Author: rajathkotyal

library/core/src/num/int_macros.rs

@@ -816,6 +816,7 @@ macro_rules! int_impl {
                       without modifying the original"]
         #[inline(always)]
         #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+        #[requires(!self.overflowing_mul(rhs).1)]
         pub const unsafe fn unchecked_mul(self, rhs: Self) -> Self {
             assert_unsafe_precondition!(
                 check_language_ub,
@@ -1424,6 +1425,7 @@ macro_rules! int_impl {
         #[rustc_const_unstable(feature = "unchecked_shifts", issue = "85122")]
         #[inline(always)]
         #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+        #[requires(rhs < <$ActualT>::BITS)] // i.e. requires the right hand side of the shift (rhs) to be less than the number of bits in the type. This prevents undefined behavior.
         pub const unsafe fn unchecked_shr(self, rhs: u32) -> Self {
             assert_unsafe_precondition!(
                 check_language_ub,

library/core/src/num/mod.rs

@@ -1605,19 +1605,39 @@ mod verify {
         }
     }
 
+    macro_rules! generate_unchecked_mul_harness {
+        ($type:ty, $method:ident, $harness_name:ident, $min:expr, $max:expr) => {
+            #[kani::proof_for_contract($type::$method)]
+            pub fn $harness_name() {
+                let num1: $type = kani::any();
+                let num2: $type = kani::any();
+    
+                // Limit the values of num1 and num2 to the specified range for multiplication
+                kani::assume(num1 >= $min && num1 <= $max);
+                kani::assume(num2 >= $min && num2 <= $max);
+    
+                unsafe {
+                    num1.$method(num2);
+                }
+            }
+        }
+    }
+    
+
     macro_rules! generate_unchecked_shift_harness {
         ($type:ty, $method:ident, $harness_name:ident) => {
             #[kani::proof_for_contract($type::$method)]
             pub fn $harness_name() {
                 let num1: $type = kani::any::<$type>();
                 let num2: u32 = kani::any::<u32>();
-
+    
                 unsafe {
                     num1.$method(num2);
                 }
             }
         }
     }
+    
 
     macro_rules! generate_unchecked_neg_harness {
         ($type:ty, $method:ident, $harness_name:ident) => {
@@ -1654,4 +1674,54 @@ mod verify {
     generate_unchecked_math_harness!(u64, unchecked_add, checked_unchecked_add_u64);
     generate_unchecked_math_harness!(u128, unchecked_add, checked_unchecked_add_u128);
     generate_unchecked_math_harness!(usize, unchecked_add, checked_unchecked_add_usize);
+
+    // unchecked_mul proofs
+    //
+    // Target types:
+    // i{8,16,32,64,128, size} and u{8,16,32,64,128, size} -- 12 types in total
+    //
+    // Target contracts:
+    // #[requires(!self.overflowing_mul(rhs).1)]
+    //
+    // Target function:
+    // pub const unsafe fn unchecked_mul(self, rhs: Self) -> Self
+    // exponential state spaces for 32,64 and 128, hence provided limited range for verification.
+    generate_unchecked_math_harness!(i8, unchecked_mul, checked_unchecked_mul_i8);
+    generate_unchecked_math_harness!(i16, unchecked_mul, checked_unchecked_mul_i16);
+    generate_unchecked_mul_harness!(i32, unchecked_mul, checked_unchecked_mul_i32, -10_000i32, 10_000i32);
+    generate_unchecked_mul_harness!(i64, unchecked_mul, checked_unchecked_mul_i64, -1_000i64, 1_000i64);
+    generate_unchecked_mul_harness!(i128, unchecked_mul, checked_unchecked_mul_i128, -1_000_000_000_000_000i128, 1_000_000_000_000_000i128);
+    generate_unchecked_mul_harness!(isize, unchecked_mul, checked_unchecked_mul_isize, -100_000isize, 100_000isize);
+    generate_unchecked_math_harness!(u8, unchecked_mul, checked_unchecked_mul_u8);
+    generate_unchecked_math_harness!(u16, unchecked_mul, checked_unchecked_mul_u16);
+    generate_unchecked_mul_harness!(u32, unchecked_mul, checked_unchecked_mul_u32, 0u32, 20_000u32);
+    generate_unchecked_mul_harness!(u64, unchecked_mul, checked_unchecked_mul_u64, 0u64, 2_000u64);
+    generate_unchecked_mul_harness!(u128, unchecked_mul, checked_unchecked_mul_u128, 0u128, 1_000_000_000_000_000u128);
+    generate_unchecked_mul_harness!(usize, unchecked_mul, checked_unchecked_mul_usize, 0usize, 100_000usize);
+
+
+    // unchecked_shr proofs
+    //
+    // Target types:
+    // i{8,16,32,64,128,size} and u{8,16,32,64,128,size} -- 12 types in total
+    //
+    // Target contracts:
+    // #[requires(rhs < <$ActualT>::BITS)]
+    //
+    // Target function:
+    // pub const unsafe fn unchecked_shr(self, rhs: u32) -> Self
+    generate_unchecked_shift_harness!(i8, unchecked_shr, checked_unchecked_shr_i8);
+    generate_unchecked_shift_harness!(i16, unchecked_shr, checked_unchecked_shr_i16);
+    generate_unchecked_shift_harness!(i32, unchecked_shr, checked_unchecked_shr_i32);
+    generate_unchecked_shift_harness!(i64, unchecked_shr, checked_unchecked_shr_i64);
+    generate_unchecked_shift_harness!(i128, unchecked_shr, checked_unchecked_shr_i128);
+    generate_unchecked_shift_harness!(isize, unchecked_shr, checked_unchecked_shr_isize);
+    generate_unchecked_shift_harness!(u8, unchecked_shr, checked_unchecked_shr_u8);
+    generate_unchecked_shift_harness!(u16, unchecked_shr, checked_unchecked_shr_u16);
+    generate_unchecked_shift_harness!(u32, unchecked_shr, checked_unchecked_shr_u32);
+    generate_unchecked_shift_harness!(u64, unchecked_shr, checked_unchecked_shr_u64);
+    generate_unchecked_shift_harness!(u128, unchecked_shr, checked_unchecked_shr_u128);
+    generate_unchecked_shift_harness!(usize, unchecked_shr, checked_unchecked_shr_usize);
+        }
+    }
 }

library/core/src/num/uint_macros.rs

@@ -908,6 +908,7 @@ macro_rules! uint_impl {
                       without modifying the original"]
         #[inline(always)]
         #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+        #[requires(!self.overflowing_mul(rhs).1)]
         pub const unsafe fn unchecked_mul(self, rhs: Self) -> Self {
             assert_unsafe_precondition!(
                 check_language_ub,
@@ -1613,6 +1614,7 @@ macro_rules! uint_impl {
         #[rustc_const_unstable(feature = "unchecked_shifts", issue = "85122")]
         #[inline(always)]
         #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+        #[requires(rhs < <$ActualT>::BITS)]// i.e. requires the right hand side of the shift (rhs) to be less than the number of bits in the type. This prevents undefined behavior.
         pub const unsafe fn unchecked_shr(self, rhs: u32) -> Self {
             assert_unsafe_precondition!(
                 check_language_ub,