RFR: 8306966: RISC-V: Support vector cast node for Vector API

[Gui Cao]

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
Testing:
qemu with UseRVV:

- [ ] Tier1 tests (release)
- [ ] Tier2 tests (release)
- [ ] Tier3 tests (release)
- [x] test/jdk/jdk/incubator/vector (fastdebug)

-------------

Commit messages:
 - 8306966: RISC-V: Support vector cast node for Vector API

Changes: https://git.openjdk.org/jdk/pull/13684/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13684&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306966
  Stats: 500 lines in 5 files changed: 444 ins; 46 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/13684.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13684/head:pull/13684

PR: https://git.openjdk.org/jdk/pull/13684