Fix signed integer overflow in RV32I

The implementation of add, sub, and addi instructions incorrectly used
int32_t for arithmetic operations, leading to signed integer overflow.
Address the issue by maintaining the uint32_t type for arithmetic
operations, ensuring compliance with the laws of arithmetic modulo 2^n.
This approach prevents undefined behavior resulting from signed integer
overflow.

Author: visitorckw

src/rv32_constopt.c

@@ -233,8 +233,7 @@ CONSTOPT(srai, {
 CONSTOPT(add, {
     if (info->is_constant[ir->rs1] && info->is_constant[ir->rs2]) {
         info->is_constant[ir->rd] = true;
-        ir->imm = (int32_t) info->const_val[ir->rs1] +
-                  (int32_t) info->const_val[ir->rs2];
+        ir->imm = info->const_val[ir->rs1] + info->const_val[ir->rs2];
         info->const_val[ir->rd] = ir->imm;
         ir->opcode = rv_insn_lui;
         ir->impl = dispatch_table[ir->opcode];
@@ -246,8 +245,7 @@ CONSTOPT(add, {
 CONSTOPT(sub, {
     if (info->is_constant[ir->rs1] && info->is_constant[ir->rs2]) {
         info->is_constant[ir->rd] = true;
-        ir->imm = (int32_t) info->const_val[ir->rs1] -
-                  (int32_t) info->const_val[ir->rs2];
+        ir->imm = info->const_val[ir->rs1] - info->const_val[ir->rs2];
         info->const_val[ir->rd] = ir->imm;
         ir->opcode = rv_insn_lui;
         ir->impl = dispatch_table[ir->opcode];

src/rv32_template.c

@@ -603,7 +603,7 @@ RVOP(
  */
 RVOP(
     addi,
-    { rv->X[ir->rd] = (int32_t) (rv->X[ir->rs1]) + ir->imm; },
+    { rv->X[ir->rd] = rv->X[ir->rs1] + ir->imm; },
     GEN({
         ld, S32, TMP0, X, rs1;
         alu32_imm, 32, 0x81, 0, TMP0, imm;
@@ -732,9 +732,7 @@ RVOP(
 /* ADD */
 RVOP(
     add,
-    {
-        rv->X[ir->rd] = (int32_t) (rv->X[ir->rs1]) + (int32_t) (rv->X[ir->rs2]);
-    },
+    { rv->X[ir->rd] = rv->X[ir->rs1] + rv->X[ir->rs2]; },
     GEN({
         ld, S32, TMP0, X, rs1;
         ld, S32, TMP1, X, rs2;
@@ -745,9 +743,7 @@ RVOP(
 /* SUB: Substract */
 RVOP(
     sub,
-    {
-        rv->X[ir->rd] = (int32_t) (rv->X[ir->rs1]) - (int32_t) (rv->X[ir->rs2]);
-    },
+    { rv->X[ir->rd] = rv->X[ir->rs1] - rv->X[ir->rs2]; },
     GEN({
         ld, S32, TMP0, X, rs1;
         ld, S32, TMP1, X, rs2;