[CIR][CIRGen][Builtin][Neon] Lower vshrd_n_s64 (#1260)

Lowering `vshrd_n_s64`

Author: AmrDeveloper

clang/lib/CIR/CodeGen/CIRGenBuiltinAArch64.cpp

@@ -3825,7 +3825,11 @@ CIRGenFunction::emitAArch64BuiltinExpr(unsigned BuiltinID, const CallExpr *E,
     return builder.createShiftLeft(Ops[0], amt->getZExtValue());
   }
   case NEON::BI__builtin_neon_vshrd_n_s64: {
-    llvm_unreachable("NEON::BI__builtin_neon_vshrd_n_s64 NYI");
+    std::optional<llvm::APSInt> amt =
+        E->getArg(1)->getIntegerConstantExpr(getContext());
+    assert(amt && "Expected argument to be a constant");
+    uint64_t bits = std::min(static_cast<uint64_t>(63), amt->getZExtValue());
+    return builder.createShiftRight(Ops[0], bits);
   }
   case NEON::BI__builtin_neon_vshrd_n_u64: {
     llvm_unreachable("NEON::BI__builtin_neon_vshrd_n_u64 NYI");

clang/test/CIR/CodeGen/AArch64/neon.c

@@ -15078,12 +15078,16 @@ int16_t test_vqmovns_s32(int32_t a) {
 //   return (uint64_t)vcaltd_f64(a, b);
 // }
 
-// NYI-LABEL: @test_vshrd_n_s64(
-// NYI:   [[SHRD_N:%.*]] = ashr i64 %a, 1
-// NYI:   ret i64 [[SHRD_N]]
-// int64_t test_vshrd_n_s64(int64_t a) {
-//   return (int64_t)vshrd_n_s64(a, 1);
-// }
+int64_t test_vshrd_n_s64(int64_t a) {
+  return (int64_t)vshrd_n_s64(a, 1);
+
+  // CIR-LABEL: vshrd_n_s64
+  // CIR: {{%.*}} = cir.shift(right, {{%.*}} : !s64i, {{%.*}} : !s64i) -> !s64i
+
+  // LLVM-LABEL: @test_vshrd_n_s64(
+  // LLVM:   [[SHRD_N:%.*]] = ashr i64 %0, 1
+  // LLVM:   ret i64 [[SHRD_N]]
+}
 
 // NYI-LABEL: @test_vshrd_n_u64(
 // NYI:   ret i64 0