[clang] [llvm] [RISCV][Zicfilp] Enable Zicfilp CFI compiler behaviors by looking at module flags (PR #152121)

[Ming-Yi Lai via llvm-commits]

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@@ -1802,3 +1800,15 @@ def FeatureTaggedGlobals : SubtargetFeature<"tagged-globals",
     "AllowTaggedGlobals",
     "true", "Use an instruction sequence for taking the address of a global "
     "that allows a memory tag in the upper address bits">;
+
+// Zicfilp-based CFI
+def FeatureZicfilpUnlabeled
+    : SubtargetFeature<
+          "zicfilp-unlabeled", "HasZicfilpUnlabeled", "true",
+          "Enforce forward-edge control-flow integrity with ZICFILP-unlabeled">;
+def FeatureZicfilpFuncSig
+    : SubtargetFeature<
+          "zicfilp-func-sig", "HasZicfilpFuncSig", "true",
+          "Enforce forward-edge control-flow integrity with ZICFILP-func-sig">;
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mylai-mtk wrote:

In the end, I decided to still implement this series of features as enum target features, since when prototyping riscv-non-isa/riscv-elf-psabi-doc#474 , the disassembler would only know that zicfilp-cfi is enabled, but has no idea about the scheme. As a result, a generic indicator target feature "zicfilp-cfi" is needed, which could be overridden by the zicfilp-unlabeled/zicfilp-func-sig enum. This kinda uses the overriding semantics of enum target features, though still not a perfect match. 

https://github.com/llvm/llvm-project/pull/152121