Merge pull request #1539 from riscv-software-src/fix-signed-overflow

Fix UB on signed overflow in mulh routine
riscv-software-src · Dec 14, 2023 · b98de6f · b98de6f
2 parents a729aff + 1cc3a1f
commit b98de6f
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/riscv/arith.h b/riscv/arith.h
@@ -33,7 +33,7 @@ inline int64_t mulh(int64_t a, int64_t b)
 {
   int negate = (a < 0) != (b < 0);
   uint64_t res = mulhu(a < 0 ? -a : a, b < 0 ? -b : b);
-  return negate ? ~res + (a * b == 0) : res;
+  return negate ? ~res + ((uint64_t)a * (uint64_t)b == 0) : res;
 }
 
 inline int64_t mulhsu(int64_t a, uint64_t b)