Feature update：
Add Zero support for the 32-bit RISC-V architecture（只修改了platform.m4,os_linux.cpp文件）
https://github.com/openjdk/jdk/pull/8284

autoconf-config.sub是一个相当旧的版本，内部没有RISC-V支持。导致riscv64-linux-gnu in script config.sub fails
Fix a configure error in RISC-V cross build
https://github.com/openjdk/jdk/pull/8420

为RISC-V添加了部分JVMCI实现，以允许使用GraalVM本机映像RISC-V LLVM后端，该后端不使用JVMCI进行代码发射。（全新添加的特性）
[JVMCI] partially implement JVMCI for RISC-V
https://github.com/openjdk/jdk/pull/9587

riscv rvv目前实现的MaxReduceV、MinReduceV、AddReduceV节点可以通过调用共享函数来实现
8296515: RISC-V: Small refactoring for MaxReductionV/MinReductionV/AddReductionV node implementation
https://github.com/openjdk/jdk/pull/11036

Add experimental Foreign Function & Memory API support for RISC-V.
8293841: RISC-V: Implementation of Foreign Function & Memory API (Preview)
https://github.com/openjdk/jdk/pull/11003

Follow up JDK-8280152, this case also exists in riscv.
Reuse runtime call trampolines
https://github.com/openjdk/jdk/pull/10260

给BarrierSetAssembler::load_at GC API增加第二个临时寄存器
Add a second temporary register for BarrierSetAssembler::load_at
https://github.com/openjdk/jdk/pull/10261

和x86不同在RISC-V上使用相同的fclass指令，isFinite
Implement isFinite intrinsic for RISC-V
https://github.com/openjdk/jdk/pull/10391

为rv增加AndReductionV, OrReductionV, XorReductionV的支持（只存在vredsum_vs，只有Addreduce存在node）
RISC-V: Support ReductionV instructions for Vector API
https://github.com/openjdk/jdk/pull/10691

Use Zicboz/cbo.zero to zero-out memory on RISC-V（全新的extension，存疑）
https://github.com/openjdk/jdk/pull/10718

Support for Zicbop/prefetch instructions on RISC-V（需要支持UseZicbop）
https://github.com/openjdk/jdk/pull/10884

porting JEP 425 (Virtual Threads) to RISC-V.
https://github.com/openjdk/jdk/pull/10917

Bug fix
MSB在特殊情况下会污染高位，加载立即数[0x7FFF_8000_0000, 0x7FFF_FFFF_FFFF]结果会变为[0xFFFF_7FFF_8000_0000, 0xFFFF_7FFF_FFFF_FFFF]
Fix correctness issue of MacroAssembler::movptr
https://github.com/openjdk/jdk/pull/8913

riscv: small refactoring for add_memory_int32/64
https://github.com/openjdk/jdk/pull/9461
rscv的add_memory_int32/64只能将符号扩展的12位立即添加到内存中，因为它们直接调用addi/addiw汇编程序。（rv中w代表4个字节）

直接返回weak CAS在macroAssembler_riscv.cpp中的结果值给riscv.ad
RISC-V: Simplify weak CAS return value handling
https://github.com/openjdk/jdk/pull/10006

移除不必要的assert_cond(masm != NULL);
https://github.com/openjdk/jdk/pull/10079

目前，G1（和Shenandoah）在riscv上的oop_store_at中隐式使用x13。将x13改为tmp3形式的隐式调用。
RISC-V: Explicitly pass a third temp register to MacroAssembler::store_heap_oop
https://github.com/openjdk/jdk/pull/10137

get/put_native_u8 misses the case when address AND 7 is 6
https://github.com/openjdk/jdk/pull/10344

缺少了析构'java_lang_ref_Reference导致构建失败
https://github.com/openjdk/jdk/pull/10368

清理RISC-V后端中虚拟指令标记用法
Cleanup InstructionMark usages in the backend
https://github.com/openjdk/jdk/pull/10369

Issue https://bugs.openjdk.org/browse/JDK-8294160同步修改到riscv中
RISC-V: Misc crash dump improvements
https://github.com/openjdk/jdk/pull/10512

Fix PaX check on RISC-V
https://github.com/openjdk/jdk/pull/10690

LIRGenerator::do_LibmInrinsic的移植逻辑存在正确性问题
Fix LIRGenerator::do_LibmIntrinsic
https://github.com/openjdk/jdk/pull/10867

使NegVI可以匹配T_SHORT/T_BYTE（mr中的测试用例jdk11没有）
8296638: RISC-V: NegVI node emits wrong code when vector element basic type is T_BYTE/T_SHORT
https://github.com/openjdk/jdk/pull/11074

encounters the same assertion failure as JDK-8295414
8296771: RISC-V: C2: assert(false) failed: bad AD file
https://github.com/openjdk/jdk/pull/11085

SkipIfEqual 会从内存加载一个flag，但是在aarch64和risc-v中没有使用到value这个输入参数。
8296630: Fix SkipIfEqual on AArch64 and RISC-V
https://github.com/openjdk/jdk/pull/11076

修复MacroAssembler::en/decode_klass_not_null中kill usages of heapbase register 的情况
8296448: RISC-V: Fix temp usages of heapbase register killed by MacroAssembler::en/decode_klass_not_null
https://github.com/openjdk/jdk/pull/11010

vrsub_vx和vrsub_vi的操作数顺序与RVV1.0规范中的操作数顺序不同
8296447: RISC-V: Make the operands order of vrsub_vx/vrsub_vi consistent with RVV 1.0 spec
https://github.com/openjdk/jdk/pull/11009

count_bytecode()，histogram_bytecode() and histogram_bytecode_pair() 修改为使用x7作为临时寄存器
8296301: Interpreter(RISC-V): Implement -XX:+PrintBytecodeHistogram and -XX:+PrintBytecodePairHistogram options
https://github.com/openjdk/jdk/pull/11051

优化：

将一些小的宏汇编函数转移到关联的头文件，这样他们有机会内联。
8296916: RISC-V: Move some small macro-assembler functions to header file
https://github.com/openjdk/jdk/pull/11130

在目前的rscv端口实现中，fence.i的使用效率低下或冗余
riscv: remove fence.i used in user space
https://github.com/openjdk/jdk/pull/9770

更改为使用“li”而不是“movptr”来实现“mv”，并统一了移动函数指针的方式。
Unify the way of moving function pointer
https://github.com/openjdk/jdk/pull/10194

使用membar代替fence的直接调用来优化assembler function， 用mv取代li来让常数移动更加统一
Use macro-assembler functions as appropriate
https://github.com/openjdk/jdk/pull/10210

remove cbuf parameter from far_call/far_jump/trampoline in riscv.
https://github.com/openjdk/jdk/pull/10277

一些方法在sharedRuntime_riscv.cpp可以被复用
RISC-V: Move rt_call and xxx_move from SharedRuntime to MacroAssembler
https://github.com/openjdk/jdk/pull/10375

将所有在 AbstractAssembler的重定位封装成relocate()
https://github.com/openjdk/jdk/pull/10384

将movptr_with_offset改为movptr来对原有的movptr进行重载。https://github.com/openjdk/jdk/pull/10439

Calling intrinsic version of Thread.currentThread() in interpreter is ~30% faster on the Unmatched board:
https://github.com/openjdk/jdk/pull/10709

修改load_heap_oop store_heap_oop load_heap_oop_not_null三个方法中 = noreg的临时寄存器。
Remove implicit noreg temp register arguments in MacroAssembler
https://github.com/openjdk/jdk/pull/10778

仅修改代码格式或注释：
https://github.com/openjdk/jdk/pull/10227

注明RISCV64 OpenJDK在生成的调用中使用不同类型的调用。修改过时的注释
https://github.com/openjdk/jdk/pull/10311

删除部分代码
Use li instead of patchable movptr at non-patchable callsites
https://github.com/openjdk/jdk/pull/10462

将assembler.cpp/hpp 中的macro-assembler functions移动到masm
https://github.com/openjdk/jdk/pull/10697

修复minimal debug build
RISC-V: Minimal builds are broken
https://github.com/openjdk/jdk/pull/10742

Rename some assembler intrinsic functions for RVV 1.0
https://github.com/openjdk/jdk/pull/10878

increment and decrement使用t1作为临时寄存器，但是t1是flag register 在c2中。
Small refactoring for increment/decrement
https://github.com/openjdk/jdk/pull/11005