Altera Nios II C2H Compiler Manual de usuario descargar pdf (Pagina 76)

3–36 9.1 Altera Corporation

Nios II C2H Compiler User Guide November 2009

Scheduling

Figure 3–16. Pointers Always Depend on Themselves

In this example, the C2H Compiler cannot schedule the two read

operations in parallel, because it assumes that the two address

expressions of my_ptr could overlap. Assuming that offset_a never

equals offset_b, to make these operations execute in parallel, you need

to declare another restricted pointer.

Figure 3–17 shows the dependency graph for Example 3–31, which

introduces a new restricted pointer, my_ptr_b, to prevent the data

dependency present in Figure 3–16.

Example 3–31. Using Another Pointer to Avoid Self-Dependence

void foo(int * __restrict__ my_ptr,

int offset_a,

int offset_b)

{

int a, b;

int * __restrict__ my_ptr_b = my_ptr;

a = my_ptr[offset_a];

my_ptr[offset_a] = a + 7;

b = my_ptr_b[offset_b];

my_ptr_b[offset_b] = b + 8;

}

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Altera Nios II C2H Compiler Manual de usuario Pagina 76