[Clang][RISCV] Implement __builtin_riscv_pause intrinsic

Author: imkiva

clang/include/clang/Basic/BuiltinsRISCV.td

@@ -147,6 +147,13 @@ def ntl_load : RISCVBuiltin<"void(...)">;
 def ntl_store : RISCVBuiltin<"void(...)">;
 } // Features = "zihintntl", Attributes = [CustomTypeChecking]
 
+//===----------------------------------------------------------------------===//
+// Zihintpause extension.
+//===----------------------------------------------------------------------===//
+let Features = "zihintpause" in {
+def pause : RISCVBuiltin<"void(...)">;
+} // Features = "zihintntl"
+
 //===----------------------------------------------------------------------===//
 // XCV extensions.
 //===----------------------------------------------------------------------===//

clang/lib/CodeGen/TargetBuiltins/RISCV.cpp

@@ -357,6 +357,12 @@ Value *CodeGenFunction::EmitRISCVBuiltinExpr(unsigned BuiltinID,
 
     return Store;
   }
+  // Zihintpause
+  case RISCV::BI__builtin_riscv_pause: {
+    llvm::Function *Fn = CGM.getIntrinsic(llvm::Intrinsic::riscv_pause);
+    return Builder.CreateCall(Fn, {});
+  }
+
   // XCValu
   case RISCV::BI__builtin_riscv_cv_alu_addN:
     ID = Intrinsic::riscv_cv_alu_addN;

clang/test/CodeGen/RISCV/riscv-zihintpause.c

@@ -0,0 +1,14 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
+// RUN: %clang_cc1 -triple riscv32 -target-feature +zihintpause -emit-llvm %s -o - \
+// RUN:     | FileCheck %s
+
+#include <stdint.h>
+
+// CHECK-LABEL: @test_builtin_pause(
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    call void @llvm.riscv.pause()
+// CHECK-NEXT:    ret void
+//
+void test_builtin_pause() {
+    __builtin_riscv_pause();
+}