Hello, would like to ask a question about neon,
I define a function in C, the participation of his request is int32, like this: the convert (SRC, DST, int32 b)
But I need use inside the function instruction vqrshrun_n_s32 (int32x4_t a, const int n) shift instruction, initialized directly with b const int n=b instruction calls again, compile error number n is not always immediately, but int c=2, and then assigned to the n is no problem, would like to ask is why, thank you.
CodePudding user response:
Reference
compile error number n is not always immediately an error, and submitted to the number of b is not always immediately; Or can try const int n=(const int) b. Conduct casts? CodePudding user response:
reference 1/f, zara's reply: reference compile error number n is not always immediately an error, and submitted to the number of b is not always immediately; Or can try const int n=(const int) b. Conduct casts? CodePudding user response:
At the same time, vshr_n_s32 instruction can be normal use, but with other prefix with same complains a suffix, such as vrshr_n_s32 instructions, CodePudding user response:
Mistake # 2 don't mean that ah, the error message is the second parameter or temp requirement must be a constant number immediately, such as 2 or 5, can't be other variables, and whether the int or const int has nothing to do; Should be the parameters corresponding to the last instructions is asking for is number immediately, can't be a register or memory, CodePudding user response:
Zara refer to 4th floor response: mistake # 2 don't mean that ah, the error message is the second parameter or temp requirement must be a constant number immediately, such as 2 or 5, can't be other variables, and whether the int or const int has nothing to do; Should be the parameters corresponding to the last instructions is asking for is number immediately, can't be a register or memory, CodePudding user response:
Zara refer to 4th floor response: mistake # 2 don't mean that ah, the error message is the second parameter or temp requirement must be a constant number immediately, such as 2 or 5, can't be other variables, and whether the int or const int has nothing to do; Should be the parameters corresponding to the last instructions is asking for is number immediately, can't be a register or memory, CodePudding user response:
You put n as the function of the second parameter is ok? Or is it just these two statements can be? If the former, you should not probably, though I didn't contact with for this, but look at the screenshot of the message and online search related function (I think I should not function but the macro definition) that are mentioned the immediate value, is the number immediately, unlike ordinary function parameters, CodePudding user response:
Vqrshrun_n_s32 (int32x4_t a, const int n) this can determine the value of n must be a compile time, not a variable CodePudding user response:
Zara reference 7 floor response: you n as the function of the second parameter is ok? Or is it just these two statements can be? If the former, you should not probably, though I didn't contact with for this, but look at the screenshot of the message and online search related function (I think I should not function but the macro definition) that are mentioned the immediate value, is the number immediately, unlike ordinary function parameters, CodePudding user response:
refer to eight floor early play play nuclear response: vqrshrun_n_s32 (int32x4_t a, const int n) this can determine the value of n must be a compile time, not is a variable CodePudding user response:
# 9 if only the two sentences could be compiler optimization into n as a fixed value, 2 a, use the scanf () function assignment again n=a, then calls the function? If can, it's strange; If not, probably just in front of the reason, 