QEMU-system ISA: rv64imafdcvh_zicbom_zicboz_zicntr_zicsr_zifencei_zihintntl_zihintpause_zihpm_zacas_zawrs_zfa_zfh_zfhmin_zca_zcd_zba_zbb_zbc_zbkb_zbs_zvbb_zve32f_zve32x_zve64d_zve64f_zve64x_zvkb_zvkned_zvknhb_zvkt_sstc

$ java -XX:+PrintFlagsFinal -version | grep Zfh
     bool UseZfh = true {ARCH diagnostic} {default}
     bool UseZfhmin = true {ARCH diagnostic} {default}

To reproduce with linux-riscv64 fastdebug build:
$ make test TEST="test/hotspot/jtreg/compiler/floatingpoint/TestSubNodeFloatDoubleNegation.java"

```
One or more @IR rules failed:

Failed IR Rules (1) of Methods (1)
----------------------------------
1) Method "public static jdk.incubator.vector.Float16 compiler.floatingpoint.TestSubNodeFloatDoubleNegation.testHalfFloat(jdk.incubator.vector.Float16)" - [Failed IR rules: 1]:
   * @IR rule 1: "@compiler.lib.ir_framework.IR(phase={DEFAULT}, applyIfPlatformAnd={}, applyIfCPUFeatureOr={}, counts={"_#SUB#_", "2"}, failOn={}, applyIfPlatform={}, applyIfPlatformOr={}, applyIfOr={}, applyIfCPUFeatureAnd={}, applyIf={}, applyIfCPUFeature={}, applyIfAnd={}, applyIfNot={})"
     > Phase "PrintIdeal":
       - counts: Graph contains wrong number of nodes:
         * Constraint 1: "(\d+(\s){2}(Sub(I|L|F|D|HF).*)+(\s){2}===.*)"
           - Failed comparison: [found] 3 = 2 [given]
             - Matched nodes (3):
               * 326 SubHF === _ 560 325 [[ 327 479 ]] !orig=[478] !jvms: Float16::valueOf @ bci:5 (line 329) Float16::subtract @ bci:9 (line 1137) TestSubNodeFloatDoubleNegation::testHalfFloat @ bci:9 (line 63)
               * 443 SubF === _ 561 442 [[ 604 ]] !jvms: Float16::subtract @ bci:8 (line 1137) TestSubNodeFloatDoubleNegation::testHalfFloat @ bci:12 (line 61)
               * 479 SubHF === _ 560 326 [[ 480 ]] !jvms: Float16::valueOf @ bci:5 (line 329) Float16::subtract @ bci:9 (line 1137) TestSubNodeFloatDoubleNegation::testHalfFloat @ bci:12 (line 61)

>>> Check stdout for compilation output of the failed methods
```

Might be related to https://bugs.openjdk.org/browse/JDK-8345298 which adds riscv backend for scalar float16 operations.