Hi,

we have added some implementations related to vector cast, It was implemented by referring to RVV v1.0 [1]. please take a look and have some reviews. Thanks a lot.

We can use the VectorReshapeTests.java[2] to print the compilation log, verify and observe the generation of nodes.

For example, we can use the following command to print the compilation log of a jtreg test case:

```
/home/zifeihan/jdk-tools/jtreg/bin/jtreg \
-v:default \
-concurrency:16 -timeout:50 \
-javaoption:-XX:+UnlockExperimentalVMOptions \
-javaoption:-XX:+UseRVV \
-javaoption:-XX:+PrintOptoAssembly \
-javaoption:-XX:LogFile=/home/zifeihan/jdk-rvv/VectorReshapeTests_PrintOptoAssembly_20230426.log \
-jdk:/home/zifeihan/jdk-rvv/build/linux-riscv64-server-fastdebug/jdk \
-compilejdk:/home/zifeihan/jdk-rvv/build/linux-x86_64-server-release/images/jdk \
/home/zifeihan/jdk/test/jdk/jdk/incubator/vector/VectorReshapeTests.java
```

#### VectorCast/VectorCastB2X/VectorCastD2X/VectorCastF2X/VectorCastI2X/VectorCastL2X/VectorCastS2X
There are too many nodes here, and the following shows the log of `VectorCastB2X` nodes:

   ```
   1ba0 ld R28, [R23, #280] # ptr, #@loadP
   1ba4 addi R29, R7, #32 # ptr, #@addP_reg_imm
   1ba8 reinterpretResize V1, V5
   1bb0 vcvtBtoX V4, V1
   1bb8 far_bgeu R29, R28, B465 #@far_cmpP_branch P=0.000100 C=-1.000000
   ```

#### VectorRearrange/VectorReinterpret

When the original vector is transformed to the target vector, if the actual number of elements of the original vector is larger than the number of elements of the target vector, a slice action is performed to provide data for the subsequent cast nodes. the slice action depends on the `VectorRearrange` and `VectorReinterpret` nodes.

The compilation log for the `VectorRearrange` node:

   ```
1f6 spill R7 -> [sp, #320] # spill size = 64
1f8 spill [sp, #128] -> V1 # vector spill size = 256
200 spill [sp, #160] -> V2 # vector spill size = 256
208 rearrange V3, V1, V2
210 spill V3 -> [sp, #96] # vector spill size = 256
218 li R11, #4 # int, #@loadConI
   ```

The compilation log for the `VectorReinterpret` node:

```
1218 spill [sp, #32] -> V4 # vector spill size = 256
1220 spill [sp, #176] -> V3 # vector spill size = 256
1228 rearrange V2, V4, V3
1230 spill [sp, #72] -> V0 # vmask spill size = 32
123c vmerge_vvm V1, V1, V2, v0 #@vector blend
1244 reinterpretResize V2, V1
124c vcvtStoX_extend V5, V2
1254 bgeu R28, R7, B169 #@cmpP_branch P=0.000100 C=-1.000000
```

#### LShiftCntV/RShiftCntV/MaskAll

We have merged `LShiftCntV`, `RShiftCntV` nodes and support boolean types

The compilation log for the LShiftCntV/RShiftCntV node:

```
24c vasrB V3, V1, V2
260 storeV [R19], V3 # vector (rvv)
268 lbu R19, [R29, #48] # byte, #@loadUB
26c andi R19, R19, #7 #@andI_reg_imm
270 loadV V1, [R25] # vector (rvv)
278 vshiftcnt V2, R19
280 vasrB V3, V1, V2
294 storeV [R26], V3 # vector (rvv)
29c lbu R19, [R29, #80] # byte, #@loadUB
2a0 andi R19, R19, #7 #@andI_reg_imm
2a4 loadV V1, [R22] # vector (rvv)
2ac vshiftcnt V2, R19
```

By the way, the mask version of MaskAll is supported.

[1] https://github.com/riscv/riscv-v-spec/blob/v1.0/v-spec.adoc

[2] https://github.com/openjdk/jdk/blob/master/test/jdk/jdk/incubator/vector/VectorReshapeTests.java