问题
I have the following function with inline assembly that works fine on debug mode in 32 bit Visual Studio 2008:
__device__ void add(int* pa, int* pb)
{
asm(".reg .u32 s<3>;"::);
asm(".reg .u32 r<14>;"::);
asm("ld.global.b32 s0, [%0];"::"r"(&pa)); //load addresses of pa, pb
printf(...);
asm("ld.global.b32 s1, [%0];"::"r"(&pb));
printf(...);
asm("ld.global.b32 r1, [s0+8];"::);
printf(...);
asm("ld.global.b32 r2, [s1+8];"::);
printf(...);
...// perform some operations
}
pa and pb are globally allocated on the device such as
__device__ int pa[3] = {0, 0x927c0000, 0x20000011};
__device__ int pb[3] = {0, 0xbb900000, 0x2000000b};
However, this code fails on release mode, on line asm("ld.global.b32 r1, [s0+8];"::);
How can I load function parameters correctly with inline ptx on release mode?
P.S. building the release mode with -G flag (Generates GPU debug info) causes the code to run correctly on release mode. Thank you,
回答1:
Hopefully this code will help. I'm still guessing at what you are trying to do exactly, but I started with your code and decided to add some values in the pa
and pb
arrays and store them back into pa[0]
and pb[0]
.
This code is written for a 64 bit machine but converting it to 32 bit pointers should not be difficult. I have marked the lines that need to be changed for 32 bit pointers with a comment. Hopefully this will answer your question about how to use function parameters that are pointers to device memory:
#include <stdio.h>
__device__ int pa[3] = {0, 0x927c0000, 0x20000011};
__device__ int pb[3] = {0, 0xbb900000, 0x2000000b};
__device__ void add(int* mpa, int* mpb)
{
asm(".reg .u64 s<2>;"::); // change to .u32 for 32 bit pointers
asm(".reg .u32 r<6>;"::);
asm("mov.u64 s0, %0;"::"l"(mpa)); //change to .u32 and "r" for 32 bit
asm("mov.u64 s1, %0;"::"l"(mpb)); //change to .u32 and "r" for 32 bit
asm("ld.global.u32 r0, [s0+4];"::);
asm("ld.global.u32 r1, [s1+4];"::);
asm("ld.global.u32 r2, [s0+8];"::);
asm("ld.global.u32 r3, [s1+8];"::);
asm("add.u32 r4, r0, r2;"::);
asm("add.u32 r5, r1, r3;"::);
asm("st.global.u32 [s0], r4;"::);
asm("st.global.u32 [s1], r5;"::);
}
__global__ void mykernel(){
printf("pa[0] = %x, pb[0] = %x\n", pa[0], pb[0]);
add(pa, pb);
printf("pa[0] = %x, pb[0] = %x\n", pa[0], pb[0]);
}
int main() {
mykernel<<<1,1>>>();
cudaDeviceSynchronize();
return 0;
}
When I run this code I get:
$ ./t128
pa[0] = 0, pb[0] = 0
pa[0] = b27c0011, pb[0] = db90000b
$
which I believe is correct output.
I compiled it with:
nvcc -O3 -arch=sm_20 -o t128 t128.cu
来源:https://stackoverflow.com/questions/16042176/load-function-parameters-in-inlined-ptx