[clang] [llvm] [RISCV][MC] Add support for Q extension (PR #139369)

[Iris Shi via cfe-commits]

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@@ -291,6 +291,13 @@ def HasStdExtD : Predicate<"Subtarget->hasStdExtD()">,
                  AssemblerPredicate<(all_of FeatureStdExtD),
                                     "'D' (Double-Precision Floating-Point)">;
 
+def FeatureStdExtQ
+    : RISCVExtension<2, 2, "Quad-Precision Floating-Point", [FeatureStdExtD]>,
+      RISCVExtensionBitmask<0, 16>;
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el-ev wrote:

It’s defined in the privileged spec, `misa` part.

https://github.com/riscv/riscv-isa-manual/blob/main/src/machine.adoc

https://github.com/llvm/llvm-project/pull/139369