Create fuzzing tests for overflowing multiplication

Author: AaronKutch

testcrate/tests/overflowing_mul.rs

@@ -0,0 +1,57 @@
+use compiler_builtins::int::mul::{
+    __mulodi4, __mulosi4, __muloti4, __rust_i128_mulo, __rust_u128_mulo,
+};
+
+#[test]
+fn overflowing_mul_test() {
+    testcrate::fuzz_2(10_000, |x: i32, y: i32| {
+        let (mul0, o0) = x.overflowing_mul(y);
+        let mut o1 = 0i32;
+        let mul1 = __mulosi4(x, y, &mut o1);
+        if mul0 != mul1 || o0 != (o1 != 0) {
+            panic!(
+                "__mulosi4({}, {}): expected: {} (oflow = {}), found: {} (oflow = {})",
+                x, y, mul0, o0, mul1, o1
+            );
+        }
+    });
+    testcrate::fuzz_2(10_000, |x: i64, y: i64| {
+        let (mul0, o0) = x.overflowing_mul(y);
+        let mut o1 = 0i32;
+        let mul1 = __mulodi4(x, y, &mut o1);
+        if mul0 != mul1 || o0 != (o1 != 0) {
+            panic!(
+                "__mulodi4({}, {}): expected: {} (oflow = {}), found: {} (oflow = {})",
+                x, y, mul0, o0, mul1, o1
+            );
+        }
+    });
+    testcrate::fuzz_2(10_000, |x: i128, y: i128| {
+        let (mul0, o0) = x.overflowing_mul(y);
+        let mut o1 = 0i32;
+        let mul1 = __muloti4(x, y, &mut o1);
+        if mul0 != mul1 || o0 != (o1 != 0) {
+            panic!(
+                "__mulodi4({}, {}): expected: {} (oflow = {}), found: {} (oflow = {})",
+                x, y, mul0, o0, mul1, o1
+            );
+        }
+        let (mul2, o2) = __rust_i128_mulo(x, y);
+        if mul0 != mul2 || o0 != o2 {
+            panic!(
+                "__rust_i128_mulo({}, {}): expected: {} (oflow = {}), found: {} (oflow = {})",
+                x, y, mul0, o0, mul2, o2
+            );
+        }
+    });
+    testcrate::fuzz_2(10_000, |x: u128, y: u128| {
+        let (mul0, o0) = x.overflowing_mul(y);
+        let (mul1, o1) = __rust_u128_mulo(x, y);
+        if mul0 != mul1 || o0 != o1 {
+            panic!(
+                "__rust_u128_mulo({}, {}): expected: {} (oflow = {}), found: {} (oflow = {})",
+                x, y, mul0, o0, mul1, o1
+            );
+        }
+    });
+}