[clang][RISCV] Accept -fcf-protection=branch when Zicfilp extension is on

-fcf-protection=branch turns on indirect branching protection on RISC-V targets
with Zicfilp extension.

Author: mylai-mtk

clang/lib/Basic/Targets/RISCV.h

@@ -131,6 +131,13 @@ class RISCVTargetInfo : public TargetInfo {
   bool supportsCpuInit() const override { return getTriple().isOSLinux(); }
   bool validateCpuSupports(StringRef Feature) const override;
   bool isValidFeatureName(StringRef Name) const override;
+
+  bool
+  checkCFProtectionBranchSupported(DiagnosticsEngine &Diags) const override {
+    if (ISAInfo->hasExtension("zicfilp"))
+      return true;
+    return TargetInfo::checkCFProtectionBranchSupported(Diags);
+  }
 };
 class LLVM_LIBRARY_VISIBILITY RISCV32TargetInfo : public RISCVTargetInfo {
 public:

clang/test/CodeGen/RISCV/riscv-cf-protection.c

@@ -0,0 +1,18 @@
+// RUN: not %clang --target=riscv32 -fcf-protection=branch -c %s \
+// RUN:   -o /dev/null 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-BRANCH-PROT-INVALID %s
+
+// RUN: not %clang --target=riscv32 -fcf-protection=branch -c %s \
+// RUN:   -o /dev/null 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-BRANCH-PROT-INVALID %s
+
+// RUN: not %clang --target=riscv64 -fcf-protection=branch -c %s \
+// RUN:   -o /dev/null 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-BRANCH-PROT-INVALID %s
+
+// RUN: not %clang --target=riscv64 -fcf-protection=branch -c %s \
+// RUN:   -o /dev/null 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-BRANCH-PROT-INVALID %s
+
+// CHECK-BRANCH-PROT-INVALID: error: option 'cf-protection=branch' cannot be
+// CHECK-BRANCH-PROT-INVALID-SAME: specified on this target