Altera Nios II C2H Compiler Manuale Utente Scaricare il pdf (Pagina 75)

Altera Corporation 9.1 3–35

November 2009 Nios II C2H Compiler User Guide

C-to-Hardware Mapping Reference

Figure 3–15. __restrict__ Pointer Type Breaks Dependencies

Although a pointer qualified with __restrict__ creates no

dependencies with other pointers, it can create dependencies with itself.

Figure 3–16 shows the dependency graph for Example 3–30.

Example 3–30. Pointers Always Depend on Themselves

void foo(int * __restrict__ my_ptr,

int offset_a,

int offset_b)

{

int a, b;

a = my_ptr[offset_a];

my_ptr[offset_a] = a + 7;

b = my_ptr[offset_b];

my_ptrb[offset_b] = b + 8;

}

1 2 ... 70 71 72 73 74 75 76 77 78 79 80 ... 137 138

Nios II C2H Compiler 1
User Guide 1
UG-N2C2HCMPLR-1.6 2
Contents 3
Chapter 6. Pragma Reference 4
1. Introduction to the 7
Target Audience 8
Introduction 8
Altera Corporation 9.1 1–5 11
C2H Compiler 12
Concepts 12
Hardware and Software 13
1–8 9.1 Altera Corporation 14
C2H Compiler Concepts 14
System Architecture 15
Appropriate for 19
Hardware 19
Acceleration 19
Poor Acceleration Candidates 20
Next Steps 22
2. Getting Started Tutorial 23
Typical Design 24
OpenCore Plus Evaluation 25
Tutorial 26
Altera Corporation 9.1 2–5 27
Getting Started Tutorial 27
Create the Software Project 28
Altera Corporation 9.1 2–7 29
2–8 9.1 Altera Corporation 30
Altera Corporation 9.1 2–9 31
Rebuild the Project 32
Remove the Accelerator 37
3. C-to-Hardware Mapping 41
Reference 41
Assignments 42
>> 44
<< 44
Iteration Statements 45
Selection Statements 46
Altera Corporation 9.1 3–7 47
Conditional Operator ?: 48
Altera Corporation 9.1 3–9 49
Subfunction Calls 51
Variable 53
Declarations 53
Scalar Variables 54
Accesses 55
Memory Accesses 58
Volatile Type Qualifier 59
Address Computation 61
Data Computation 62
Master-Slave Connections 63
Array Subscript Operator 66
Structure and Union Operators 68
Scheduling 70
Data Dependencies 71
Pointer Aliasing 72
int offset_b) 75
my_ptr[offset_a] = a + 7; 75
my_ptrb[offset_b] = b + 8; 75
Read Operations with Latency 77
Stalling 79
Loop Pipelining 82
Loop-Carried Dependencies 84
Subfunction Pipelining 89
Resource 91
Resource Sharing 92
4. Understanding the C2H 95
Configuration Meaning 96
Altera Corporation 9.1 4–5 99
4–6 9.1 Altera Corporation 100
Resources 100
Altera Corporation 9.1 4–7 101
Understanding the C2H View 101
4–8 9.1 Altera Corporation 102
Altera Corporation 9.1 4–9 103
Performance 104
Loop Latency 105
Scheduling Information 108
Further Reading 113
5. Accelerating Code Using 115
Tools Command Line 115
Altera Corporation 9.1 5–3 117
5–4 9.1 Altera Corporation 118
C2H Performance Metrics 118
6. Pragma Reference 119
Reducing Arbitration Logic 120
Flow Control 121
Interrupt 122
Unshare Pointer 123
6–6 9.1 Altera Corporation 124
Unshare Pointer Pragma 124
7. ANSI C Compliance and 125
Restrictions 125
7–2 9.1 Altera Corporation 126
Language 126
Expressions 127
Functions 128
Altera Corporation 9.1 7–5 129
7–6 9.1 Altera Corporation 130
Altera Corporation 9.1 7–7 131
Goto (Section 6.8.6.1) 132
Other Restrictions 134
Additional Information 135
Revision History 136
How to Contact 137
Typographic 137
Conventions 137
Visual Cue Meaning 138

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