RFR: 8319705: RISC-V: signumF/D intrinsics fails compiler/intrinsics/math/TestSignumIntrinsic.java [v3]

[Hamlin Li]

> Hi,
> Can you review the patch to fix the bug introduced by [JDK-8317971](https://bugs.openjdk.org/browse/JDK-8317971) which implemented signumF/D intrinsics.
> But seems the intrinsics failed since day 1 (I checkouted the commit to verify it.)
> Thanks
> 
> ## Test
> hotspot tests:
> 
> test/hotspot/jtreg/compiler/intrinsics/math/TestSignumIntrinsic.java
> test/hotspot/jtreg/compiler/c2/PolynomialRoot.java
> 
> 
> other jdk tests contains Math.signum(...):
> 
> test/jdk/java/math/BigInteger/BigIntegerTest.java 
> test/jdk/java/math/BigInteger/largeMemory/DivisionOverflow.java
> test/jdk/java/math/BigInteger/SerializationTests.java
> test/jdk/java/math/BigInteger/ModInvTime.java
> test/jdk/java/math/BigDecimal/SquareRootTests.java
> test/jdk/java/math/BigDecimal/DivideTests.java
> test/jdk/java/lang/Math/IeeeRecommendedTests.java
> test/jdk/java/lang/Math/IeeeRemainderTests.java

Hamlin Li has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:

 - use t0 directly instead of get another tmp from reg allocator
 - Merge branch 'master' into fix-signum
 - remove rFlagsReg
 - Kill cr
 - Initial commit

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16557/files
  - new: https://git.openjdk.org/jdk/pull/16557/files/509764b5..85de9252

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16557&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16557&range=01-02

  Stats: 2384 lines in 59 files changed: 1521 ins; 513 del; 350 mod
  Patch: https://git.openjdk.org/jdk/pull/16557.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16557/head:pull/16557

PR: https://git.openjdk.org/jdk/pull/16557