As RISC-V spec supports multiple extension version, refactor the SubtargetFeatures and RISCVISAInfo to support it. RISCVISAInfo can parse arch string like -march with extension version, but related SubtargetFeatures don't contain version info in llvm side. For example, SubtargetFeature name is "m" when enable 'm' extension with passing `-mattr=+m`. After this patch, it would be `-mattr=+m2p0`. It also handles arch string with version number of attribute section in obj file, including assemble and dis-assemble process. This is the whole picture of change. Because the testcase change is too huge to review, split the source change without testcase into https://reviews.llvm.org/D115923.

As RISC-V spec supports multiple extension version, refactor the SubtargetFeatures and RISCVISAInfo to support it. RISCVISAInfo can parse arch string like -march with extension version, but related SubtargetFeatures don't contain version info in llvm side. For example, when enable 'm' extension with passing `-mattr=+m`, only a boolean flag to indicate that 'm' extension is enable. After this patch, '+m' would be default -mattr to represent default extension version. You can add new extension version by adding new SubtargetFeature like +m2p1. Add 2 extensions "v0p7" and "zvlsseg0p7" to test the infra, although we may not support those 2 extensions. It also handles arch string with version number of attribute section in obj file, including assemble and dis-assemble process.

As RISC-V spec supports multiple extension version, refactor the SubtargetFeatures and RISCVISAInfo to support it. RISCVISAInfo can parse arch string like -march with extension version, but related SubtargetFeatures don't contain version info in llvm side. For example, SubtargetFeature name is "m" when enable 'm' extension with passing `-mattr=+m`, only a boolean flag to indicate that 'm' extension is enable. After this patch, '+m' would be default -mattr to represent default extension version. it would be `-mattr=You can add new extension version by adding new SubtargetFeature like +m2p0`1. It also handles arch string with version number of attribute section in obj fileAdd 2 extensions "v0p7" and "zvlsseg0p7" to test the infra, including assemble and dis-assemble processalthough we may not support those 2 extensions. This is the whole picture of change. Because the testcase change is too huge to reviewIt also handles arch string with version number of attribute section in obj file, split the source change without testcase into https://reviews.llvm.org/D115923including assemble and dis-assemble process.