我正在尝试找到一种从CUDA C调用ptx函数(.func)的方法。
说我有一个这样的ptx函数:
.func (.reg .s32 %res) inc_ptr ( .reg .s32 %ptr, .reg .s32 %inc )
{
add.s32 %res, %ptr, %inc;
ret;
}
call (%d), inc_ptr, (%s, %d);
最佳答案
可以使用CUDA 5.0引入的独立编译工具来完成此操作。我不认为有办法在“整体”程序编译模式下或CUDA 5.0之前的工具包版本中或在3.1之前的PTX版本中执行此操作。
用一个可行的例子来说明如何做到这一点可能是最容易的。让我们从一个简单的PTX函数开始，该函数用于增加指针，类似于您的示例:
.version 3.1
.target sm_30
.address_size 32
.visible .func inc_ptr(.param .b32 ptr, .param .b32 inc)
{
.reg .s32 %r<6>;
ld.param.u32 %r1, [ptr];
ld.param.u32 %r2, [inc];
ld.u32 %r3, [%r1];
ld.u32 %r4, [%r3];
add.s32 %r5, %r4, %r2;
st.u32 [%r3], %r5;
ret;
}
ptxas将其编译为可重定位的设备对象，然后打包到胖容器文件中。后面的步骤似乎很关键。默认的ptxas输出仅是可重定位的elf对象，不生成任何胖容器。看来nvcc运行的设备代码链接阶段(至少在CUDA 5中)期望所有设备代码都存在于胖容器中。否则链接将失败。结果看起来像这样:$ ptxas -arch=sm_30 -c -o inc_ptr.gpu.o inc_ptr.ptx
$ fatbinary -arch=sm_30 -create inc_ptr.fatbin -elf inc_ptr.gpu.o
$ cuobjdump -sass inc_ptr.fatbin
Fatbin elf code:
================
arch = sm_30
code version = [1,6]
producer = <unknown>
host = mac
compile_size = 32bit
code for sm_30
Function : inc_ptr
/*0008*/ /*0x0040dc8580000000*/ LD R3, [R4];
/*0010*/ /*0x00301c8580000000*/ LD R0, [R3];
/*0018*/ /*0x14001c0348000000*/ IADD R0, R0, R5;
/*0020*/ /*0x00301c8590000000*/ ST [R3], R0;
/*0028*/ /*0x00001de790000000*/ RET;
/*0030*/ /*0x00001de440000000*/ NOP CC.T;
/*0038*/ /*0x00001de440000000*/ NOP CC.T;
/*0040*/ /*0xe0001de74003ffff*/ BRA 0x40;
/*0048*/ /*0x00001de440000000*/ NOP CC.T;
/*0050*/ /*0x00001de440000000*/ NOP CC.T;
/*0058*/ /*0x00001de440000000*/ NOP CC.T;
/*0060*/ /*0x00001de440000000*/ NOP CC.T;
/*0068*/ /*0x00001de440000000*/ NOP CC.T;
/*0070*/ /*0x00001de440000000*/ NOP CC.T;
/*0078*/ /*0x00001de440000000*/ NOP CC.T;
........................
extern "C" __device__ void inc_ptr(int* &ptr, const int inc);
__global__
void memsetkernel(int *inout, const int val, const int N)
{
int stride = blockDim.x * gridDim.x;
int *p = inout;
inc_ptr(p, threadIdx.x + blockDim.x*blockIdx.x);
for(; p < inout+N; inc_ptr(p, stride)) *p = val;
}
int main(void)
{
const int n=10;
int *p;
cudaMalloc((void**)&p, sizeof(int)*size_t(n));
memsetkernel<<<1,32>>>(p, 5, n);
return 0;
}
extern声明，并且(只要您在控制下进行符号处理)，设备函数fatbinary可以与其他设备和主机代码链接以产生最终对象:$ nvcc -arch=sm_30 -Xptxas="-v" -dlink -o memset.out inc_ptr.fatbin memset_kernel.cu
ptxas info : 0 bytes gmem
ptxas info : Compiling entry function '_Z12memsetkernelPiii' for 'sm_30'
ptxas info : Function properties for _Z12memsetkernelPiii
8 bytes stack frame, 0 bytes spill stores, 0 bytes spill loads
ptxas info : Used 20 registers, 332 bytes cmem[0]
$ cuobjdump -sass memset.out
Fatbin elf code:
================
arch = sm_30
code version = [1,6]
producer = <unknown>
host = mac
compile_size = 32bit
identifier = inc_ptr.fatbin memset_kernel.cu
code for sm_30
Function : _Z12memsetkernelPiii
/*0008*/ /*0x10005de428004001*/ MOV R1, c [0x0] [0x44];
/*0010*/ /*0x20105d034800c000*/ IADD R1, R1, -0x8;
/*0018*/ /*0x00019de428004005*/ MOV R6, c [0x0] [0x140];
/*0020*/ /*0x10101c034800c000*/ IADD R0, R1, 0x4;
/*0028*/ /*0x8400dc042c000000*/ S2R R3, SR_Tid_X;
/*0030*/ /*0x90041c0348004000*/ IADD R16, R0, c [0x0] [0x24];
/*0038*/ /*0x94001c042c000000*/ S2R R0, SR_CTAid_X;
/*0048*/ /*0xd0009de428004000*/ MOV R2, c [0x0] [0x34];
/*0050*/ /*0x91045d0348004000*/ IADD R17, R16, -c [0x0] [0x24];
/*0058*/ /*0x40011de428000000*/ MOV R4, R16;
/*0060*/ /*0xa0015ca320064000*/ IMAD R5, R0, c [0x0] [0x28], R3;
/*0068*/ /*0x01119c85c8000000*/ STL [R17], R6;
/*0070*/ /*0xa0209ca350004000*/ IMUL R2, R2, c [0x0] [0x28];
/*0078*/ /*0x0001000710000000*/ JCAL 0x0;
/*0088*/ /*0x0110dc85c0000000*/ LDL R3, [R17];
/*0090*/ /*0x20001de428004005*/ MOV R0, c [0x0] [0x148];
/*0098*/ /*0x00049c4340004005*/ ISCADD R18, R0, c [0x0] [0x140], 0x2;
/*00a0*/ /*0x4831dc031b0e0000*/ ISETP.GE.U32.AND P0, pt, R3, R18, pt;
/*00a8*/ /*0x000001e780000000*/ @P0 EXIT;
/*00b0*/ /*0x1004dde428004005*/ MOV R19, c [0x0] [0x144];
/*00b8*/ /*0x0034dc8590000000*/ ST [R3], R19;
/*00c8*/ /*0x40011de428000000*/ MOV R4, R16;
/*00d0*/ /*0x08015de428000000*/ MOV R5, R2;
/*00d8*/ /*0x0001000710000000*/ JCAL 0x0;
/*00e0*/ /*0x0110dc85c0000000*/ LDL R3, [R17];
/*00e8*/ /*0x4831dc03188e0000*/ ISETP.LT.U32.AND P0, pt, R3, R18, pt;
/*00f0*/ /*0x000001e74003ffff*/ @P0 BRA 0xb8;
/*00f8*/ /*0x00001de780000000*/ EXIT;
/*0100*/ /*0xe0001de74003ffff*/ BRA 0x100;
/*0108*/ /*0x00001de440000000*/ NOP CC.T;
/*0110*/ /*0x00001de440000000*/ NOP CC.T;
/*0118*/ /*0x00001de440000000*/ NOP CC.T;
/*0120*/ /*0x00001de440000000*/ NOP CC.T;
/*0128*/ /*0x00001de440000000*/ NOP CC.T;
/*0130*/ /*0x00001de440000000*/ NOP CC.T;
/*0138*/ /*0x00001de440000000*/ NOP CC.T;
.....................................
Function : inc_ptr
/*0008*/ /*0x0040dc8580000000*/ LD R3, [R4];
/*0010*/ /*0x00301c8580000000*/ LD R0, [R3];
/*0018*/ /*0x14001c0348000000*/ IADD R0, R0, R5;
/*0020*/ /*0x00301c8590000000*/ ST [R3], R0;
/*0028*/ /*0x00001de790000000*/ RET;
/*0030*/ /*0x00001de440000000*/ NOP CC.T;
/*0038*/ /*0x00001de440000000*/ NOP CC.T;
/*0040*/ /*0xe0001de74003ffff*/ BRA 0x40;
/*0048*/ /*0x00001de440000000*/ NOP CC.T;
/*0050*/ /*0x00001de440000000*/ NOP CC.T;
/*0058*/ /*0x00001de440000000*/ NOP CC.T;
/*0060*/ /*0x00001de440000000*/ NOP CC.T;
/*0068*/ /*0x00001de440000000*/ NOP CC.T;
/*0070*/ /*0x00001de440000000*/ NOP CC.T;
/*0078*/ /*0x00001de440000000*/ NOP CC.T;
........................
https://stackoverflow.com/questions/11116722/