[llvm-dev] builtins name mangling in SPIR 2.0

Liu, Yaxun (Sam) via llvm-dev llvm-dev at lists.llvm.org
Mon Sep 12 13:42:24 PDT 2016

If you use the default header file under clang/lib/Headers/opencl-c.h, get_global_id will be mangled.

If you want to declare get_global_id in your own header, add __attribute__((overloadable)), then it will be mangled.


From: Hongbin Zheng [mailto:etherzhhb at gmail.com]
Sent: Monday, September 12, 2016 4:21 PM
To: cfe-dev at lists.llvm.org; llvm-dev <llvm-dev at lists.llvm.org>; Liu, Yaxun (Sam) <Yaxun.Liu at amd.com>
Subject: builtins name mangling in SPIR 2.0

Hi all,

According to the SPIR 2.0 spec[1], the name of OpenCL builtins are mangled.

However, when I compile OpenCl code with Clang 3.9 with the "spir64-unknown-unknown" target, Clang generates IR without mangling the builtins, e.g. for:

__kernel void input_zip_int(__global int *in0) {
  *in0 = get_global_id(0);

clang generates:

define spir_kernel void @input_zip_int(i32 addrspace(1)* nocapture %in0) local_unnamed_addr #0 !kernel_arg_addr_space !3 !kernel_arg_access_qual !4 !kernel_arg_type !5 !kernel_arg_base_type !5 !kernel_arg_type_qual !6 {
  %call = tail call spir_func i128 @get_global_id(i32 0) #2
  %conv = trunc i128 %call to i32
  store i32 %conv, i32 addrspace(1)* %in0, align 4, !tbaa !7
  ret void

In this case, get_global_id is not mangled to _Z13get_global_idj according to [2].

Is there an option for clang or an LLVM clang to do the mangling for spir builtins?


[1] https://www.khronos.org/registry/spir/specs/spir_spec-2.0.pdf, page 36
[2] https://github.com/KhronosGroup/SPIR-Tools/wiki/SPIR-2.0-built-in-functions
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