LLVM OCaml绑定是否包含内在支持？

Question

我似乎无法在官方LLVM OCaml绑定中找到对内在函数的引用,超出了is_intrinsic函数.

我正在构建一个后端,需要执行一些特定于目标的代码生成(对于SSE,AVX和NEON),而内在函数是C++ API中的标准路径.

Answer 1

OCaml绑定支持内在函数的方式与C语言绑定完全相同:

在接口中没有对它们的特殊支持(就像在完整的C++接口中那样),但是它们可以被声明为extern并且像任何其他函数一样被调用.

例如:

open Llvm

let () =
  let c = create_context () in

  let f32_t = float_type c in
  let f32x4_t = vector_type f32_t 4 in

  let m = create_module c "test" in

  (* declare void @printv(<4 x float>)
   * nonce extern which forces preservation of vector results *)
  let printv =
   declare_function "printv"
     (function_type (void_type c) [|f32x4_t|]) m in

  (* declare <4 x float> @llvm.x86.sse.sqrt.ps(<4 x float>) nounwind readnone *)
  let sqrtps =
   declare_function "llvm.x86.sse.sqrt.ps"
     (function_type f32x4_t [|f32x4_t|]) m in

  (* define i32 @main() { entry: *)
  let main = define_function "main" (function_type i32_t [| |]) m in
  let at_entry = builder_at_end c (entry_block main) in

  (*%sqrtps = call <4 x float> @llvm.x86.sse.sqrt.ps(<4 x float> <float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00>)*)
  let cv1234 = const_vector [| const_float f32_t 1.0; const_float f32_t 2.0;
  const_float f32_t 3.0; const_float f32_t 4.0 |] in
  let sqrt = build_call sqrtps [| cv1234 |] "sqrtps" at_entry in

  (* call void printv(sqrtps) *)
  ignore (build_call printv [| sqrt |] "" at_entry);

  (* ret void *)
  ignore (build_ret (const_null i32_t) at_entry);

  (* Print .ll to stderr *)
  dump_module m

生产:

; ModuleID = 'test'

declare void @printv(<4 x float>)

declare <4 x float> @llvm.x86.sse.sqrt.ps(<4 x float>) nounwind readnone

define i32 @main() {
entry:
  %sqrtps = call <4 x float> @llvm.x86.sse.sqrt.ps(<4 x float> <float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00>)
  call void @printv(<4 x float> %sqrtps)
  ret i32 0
}

其编译成86正确地调用sqrtps的xmm寄存器.