[clang][RISCV] Introduce command line options for RISC-V Zicfilp CFI

This patch enables the following command line flags for RISC-V targets:

+ `-fcf-protection=branch` turns on forward-edge control-flow integrity conditioning
+ `-mcf-branch-label-scheme=unlabeled|func-sig` selects the label scheme used in the forward-edge CFI conditioning

1 files changed, 10 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index d53d479..2381fa9 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -1164,6 +1164,16 @@ void CodeGenModule::Release() {
     // Indicate that we want to instrument branch control flow protection.
     getModule().addModuleFlag(llvm::Module::Min, "cf-protection-branch",
                               1);
+
+    auto Scheme = CodeGenOpts.getCFBranchLabelScheme();
+    if (Target.checkCFBranchLabelSchemeSupported(Scheme, getDiags())) {
+      if (Scheme == CFBranchLabelSchemeKind::Default)
+        Scheme = Target.getDefaultCFBranchLabelScheme();
+      getModule().addModuleFlag(
+          llvm::Module::Error, "cf-branch-label-scheme",
+          llvm::MDString::get(getLLVMContext(),
+                              getCFBranchLabelSchemeFlagVal(Scheme)));
+    }
   }
 
   if (CodeGenOpts.FunctionReturnThunks)