[cfe-dev] builtins name mangling in SPIR 2.0

Liu, Yaxun (Sam) via cfe-dev cfe-dev at lists.llvm.org
Fri Sep 16 08:10:22 PDT 2016

+ Alexey Anastasia

According to SPIR spec v1.2 s2.10.3

2.10.3 The printf function
The printf function is supported, and is mangled according to its prototype as follows:
int printf(constant char * restrict fmt, ... )
Note that the ellipsis formal argument (...) is mangled to argument type specifier z

It seems printf should be mangled.


What do you think? Thanks.


From: Hongbin Zheng [mailto:etherzhhb at gmail.com]
Sent: Friday, September 16, 2016 1:54 AM
To: Liu, Yaxun (Sam) <Yaxun.Liu at amd.com>
Cc: cfe-dev at lists.llvm.org; llvm-dev <llvm-dev at lists.llvm.org>
Subject: Re: builtins name mangling in SPIR 2.0

Hi Sam and others,

I saw that in [1], printf is mangled to _Z6printfPrU3AS2cz, while in clang's opencl-c.h[2], printf does not have the overload attribute:
int printf(__constant const char* st, ...); (and it is different from the standard, which is printf(restrict __constant char *, ...))
I try the following code:
#include <opencl-c.h>

__kernel void vadd(__global const int* a, __global const int* b, __global int* c) {

and get a printf that is not mangled:
  %call = tail call spir_func i32 (i8 addrspace(2)*, ...) @printf(i8 addrspace(2)* getelementptr inbounds ([6 x i8], [6 x i8] addrspace(2)* @.str, i64 0, i64 0))

with the following command line:
clang -cc1 -internal-isystem /wrk/xsjhdnobkup2/hongbinz/omp/build-llvm/bin/../lib/clang/3.9.0/include -nostdsysteminc -S -emit-llvm -o -

Is this the correct behavior?


[1] https://github.com/KhronosGroup/SPIR-Tools/wiki/SPIR-2.0-built-in-functions
[2] http://clang.llvm.org/doxygen/opencl-c_8h_source.html

On Mon, Sep 12, 2016 at 1:43 PM, Hongbin Zheng <etherzhhb at gmail.com<mailto:etherzhhb at gmail.com>> wrote:
Thanks a lot.

On Mon, Sep 12, 2016 at 1:42 PM, Liu, Yaxun (Sam) <Yaxun.Liu at amd.com<mailto:Yaxun.Liu at amd.com>> wrote:
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<mailto:etherzhhb at gmail.com>]
Sent: Monday, September 12, 2016 4:21 PM
To: cfe-dev at lists.llvm.org<mailto:cfe-dev at lists.llvm.org>; llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>>; Liu, Yaxun (Sam) <Yaxun.Liu at amd.com<mailto: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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