[RISCV] 'K'-extension ordering

[a4lg]

Summary

This commit adds 'K' to supported extension list (before 'J').
It makes "Zk*" extensions correctly placed before "Zv*" extensions.

Multi-letter "Z*" extensions are first ordered with the most closely
related alphabetical extension category ("IMAF..."). This is represented
in LLVM as AllStdExts' variable in llvm/lib/Support/RISCVISAInfo.cpp'.

However, it did not have 'k' making "Zk*" extensions not correctly ordered.

[kito-cheng]

LGTM, let me know if you need me to commit that.

[a4lg]

Thanks.

It looks relaxed ordering will be appear soon but canonical ordering is needed for now.
I request for merge.

[kito-cheng]

It looks relaxed ordering will be appear soon but canonical ordering is needed for now.

Even the -march is relaxed I believe we still need canonical ordering for ELF attribute emission and multi-lib search :)

llvm/lib/Support/RISCVISAInfo.cpp

 struct RISCVSupportedExtension {
   const char *Name;
   /// Supported version.
   RISCVExtensionVersion Version;
 };
 
 } // end anonymous namespace
 
-static constexpr StringLiteral AllStdExts = "mafdqlcbjtpvn";
+static constexpr StringLiteral AllStdExts = "mafdqlcbkjtpvn";
 
 static const RISCVSupportedExtension SupportedExtensions[] = {
     {"i", RISCVExtensionVersion{2, 0}},
     {"e", RISCVExtensionVersion{1, 9}},
     {"m", RISCVExtensionVersion{2, 0}},
     {"a", RISCVExtensionVersion{2, 0}},
     {"f", RISCVExtensionVersion{2, 0}},
     {"d", RISCVExtensionVersion{2, 0}},

llvm/test/MC/RISCV/attribute-arch.s

 .attribute arch, "rv32i_zks1p0"
 # CHECK: attribute      5, "rv32i2p0_zbkb1p0_zbkc1p0_zbkx1p0_zks1p0_zksed1p0_zksh1p0"
 
 .attribute arch, "rv32i_zkt1p0"
 # CHECK: attribute      5, "rv32i2p0_zkt1p0"
 
 .attribute arch, "rv32i_zk1p0"
 # CHECK: attribute      5, "rv32i2p0_zbkb1p0_zbkc1p0_zbkx1p0_zk1p0_zkn1p0_zknd1p0_zkne1p0_zknh1p0_zkr1p0_zkt1p0"
+
+.attribute arch, "rv32if_zkt1p0_zve32f1p0_zve32x1p0_zvl32b1p0"
+# CHECK: attribute      5, "rv32i2p0_f2p0_zkt1p0_zve32f1p0_zve32x1p0_zvl32b1p0"