[RISCV] Add support for interrupt attribute

Summary:
Clang supports the GNU style ``__attribute__((interrupt))`` attribute  on RISCV targets.
Permissible values for this parameter are user, supervisor, and machine.
If there is no parameter, then it defaults to machine.
Reference: https://gcc.gnu.org/onlinedocs/gcc/RISC-V-Function-Attributes.html
Based on initial patch by Zhaoshi Zheng.

Reviewers: asb, aaron.ballman

Reviewed By: asb, aaron.ballman

Subscribers: rkruppe, the_o, aaron.ballman, MartinMosbeck, brucehoult, rbar, johnrusso, simoncook, sabuasal, niosHD, kito-cheng, shiva0217, zzheng, edward-jones, mgrang, rogfer01, cfe-commits

Differential Revision: https://reviews.llvm.org/D48412

llvm-svn: 338045

1 files changed, 21 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index 2078ea1fea0..fa9b0a27af2 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -8971,6 +8971,27 @@ class RISCVTargetCodeGenInfo : public TargetCodeGenInfo {
 public:
   RISCVTargetCodeGenInfo(CodeGen::CodeGenTypes &CGT, unsigned XLen)
       : TargetCodeGenInfo(new RISCVABIInfo(CGT, XLen)) {}
+
+  void setTargetAttributes(const Decl *D, llvm::GlobalValue *GV,
+                           CodeGen::CodeGenModule &CGM) const override {
+    const auto *FD = dyn_cast_or_null<FunctionDecl>(D);
+    if (!FD) return;
+
+    const auto *Attr = FD->getAttr<RISCVInterruptAttr>();
+    if (!Attr)
+      return;
+
+    const char *Kind;
+    switch (Attr->getInterrupt()) {
+    case RISCVInterruptAttr::user: Kind = "user"; break;
+    case RISCVInterruptAttr::supervisor: Kind = "supervisor"; break;
+    case RISCVInterruptAttr::machine: Kind = "machine"; break;
+    }
+
+    auto *Fn = cast<llvm::Function>(GV);
+
+    Fn->addFnAttr("interrupt", Kind);
+  }
 };
 } // namespace