[riscv64] FCVT_WU_D/S should signed extension the result.

Bug: v8:12132
Change-Id: Ib81c4141a07ad5269eb0abda839ebc42b8170170
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3114159
Auto-Submit: Yahan Lu <yahan@iscas.ac.cn>
Commit-Queue: Ji Qiu <qiuji@iscas.ac.cn>
Reviewed-by: Ji Qiu <qiuji@iscas.ac.cn>
Cr-Commit-Position: refs/heads/main@{#76447}

src/execution/riscv64/simulator-riscv64.cc

@@ -2376,7 +2376,8 @@ void Simulator::DecodeRVRFPType() {
           break;
         }
         case 0b00001: {  // RO_FCVT_WU_S
-          set_rd(RoundF2IHelper<uint32_t>(original_val, instr_.RoundMode()));
+          set_rd(sext32(
+              RoundF2IHelper<uint32_t>(original_val, instr_.RoundMode())));
           break;
         }
 #ifdef V8_TARGET_ARCH_64_BIT
@@ -2651,7 +2652,8 @@ void Simulator::DecodeRVRFPType() {
           break;
         }
         case 0b00001: {  // RO_FCVT_WU_D
-          set_rd(RoundF2IHelper<uint32_t>(original_val, instr_.RoundMode()));
+          set_rd(sext32(
+              RoundF2IHelper<uint32_t>(original_val, instr_.RoundMode())));
           break;
         }
 #ifdef V8_TARGET_ARCH_64_BIT