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Chapter 7 Code Optimization
AutoCode Reference 7-4 ni.com
iinfo[1] = 0;
}
return;
EXEC_ERROR: ERROR_FLAG[1] = iinfo[0];
iinfo[0]=0;}}
AutoCode performs this optimization only if it is safe to do so. There
could be circumstances that could potentially prevent this optimization
from taking place. AutoCode looks for the presence of a
write-to-the-same-variable block between the Read from Variable block
statement and its use in later computations. AutoCode does not optimize
variable blocks under these circumstances, as doing so would change the
meaning of the program.
The subsystem code in Example 7-1 actually uses two global variable
blocks, namely
var and var1. Example 7-2 shows the code generated with
global variable block optimization turned on. While variable block
var1
is used directly in the summation block computation, an extra variable
new_11_1 is used for the variable block var. This is because there is a
Write to Variable block (modifying
var) present in between the Read from
Variable block and its use in a summation block.
Optimization of local and global variables can be controlled independently.
The command-line arguments
-Olvarblk and -Ogvarblk bring about the
optimization of extra variables associated with the Read from local and
global variable blocks, respectively.
Notice that the global variable block optimization will work only if they are
not shared between subsystems or only if the
-vbco option is not used.
The following items could prevent AutoCode from optimizing Read from
Variable blocks.
• Presence of Write to the same variable block in between a Read from
Variable block and its use.
• Existence of a Procedure SuperBlock (Writing to the variable block)
between the Read from Variable block and its use.
• A dynamic block is connected to a Read from Variable block, and there
is a Write to same variable block in the subsystem (or procedure).
Since state UPDATE is done toward the end of the subsystem, the
Write to Variable block comes in between the Read from Variable
block and its use (in the state update).
• A Read from Variable block is outside a while loop, and the block
reading this variable block is inside the loop. The loop also contains a
- NI MATRIXx 1
- Important Information 3
- Conventions 4
- Chapter 3 6
- Ada Language Reference 6
- Chapter 4 8
- Chapter 5 8
- Contents 10
- AutoCode Reference x ni.com 10
- Chapter 6 11
- Vectorized Code Generation 11
- AutoCode Reference xii ni.com 12
- Appendix A 13
- Introduction 14
- General Information 15
- Configuration File 15
- Language-Specific Information 15
- Using MATRIXx Help 16
- Related Publications 17
- C Language Reference 18
- Stand-Alone Library 19
- AutoCode Reference 2-4 ni.com 21
- Target-Specific Utilities 22
- AutoCode Reference 2-6 ni.com 23
- AutoCode Reference 2-8 ni.com 25
- UserCode Blocks 27
- Implementing Handwritten UCBs 30
- File Name: usr_dsp.c 32
- Fleming: usr_dsp.c 34
- Function Name: usr_dsp 34
- Variable Interface UCB 35
- Interface Ordering 35
- Function Prototype 36
- Procedure SuperBlocks 37
- Generate Reusable Procedure 40
- Function 41
- C Fixed-Point Arithmetic 43
- Fixed-Point Data Types 45
- User Types 47
- Overflow Protection 48
- Stand-Alone Files 48
- Macro Interface 49
- Function Interface 50
- Conversion Macros 52
- 8-bit number with a shift of 53
- i ALIGN so wo p (n, rp) 54
- Arithmetic Macros 55
- 32-Bit Multiplication 59
- 32-Bit Division 60
- 16-Bit by 8-Bit Division 60
- 32-Bit by 16-Bit Division 60
- Fixed-Point Relational Macros 61
- Some Relevant Issues 62
- Supplied Templates 64
- (or sa_utils.ada), the 66
- Data Types 67
- Error Procedure( ) Procedure 69
- AutoCode Reference 3-8 ni.com 70
- External_Input ( ) Procedure 72
- Calling UCBs 74
- Ada Fixed-Point Arithmetic 78
- Generic Functions 79
- Instantiated Functions 79
- Package Dependencies 80
- Compilation Example 83
- Fixed-Point Type Declarations 85
- Bit-Wise Functions 88
- Operator Instantiations 88
- Sample Package 90
- Conversion Functions 93
- Language-Defined Conversion 94
- Truncation Conversion 94
- Explicit Rounding Conversion 94
- Known Ada Compiler Problems 97
- No-Op Conversion Function 98
- Operating Systems 100
- Configuration Items 101
- Table Syntax 101
- Scheduler Priority Table 103
- Subsystem Table 103
- AutoCode Reference 4-6 ni.com 105
- Processor IP Name Table 106
- Version Table 107
- Using the Configuration File 107
- Generated Code Architecture 109
- Signal Naming 110
- Duplicate Names 110
- Selection of a Signal Name 110
- Global Storage 111
- -vbco option is not used 112
- Subsystems 113
- Top-Level SuperBlock 114
- Block Ordering 114
- Interface Layers 114
- Sys_ExtIn and Sys_ExtOut, to 115
- Single-Rate System 116
- Multi-Rate System 116
- Sample and Hold 116
- Static Data Within Subsystems 117
- R_P and I_P 117
- State Data 117
- Procedure Data 118
- Pre-init Phase 118
- Copy Back and Duplicates 118
- Standard Procedures 119
- Unrolled Interface 120
- Phases and Error Handling 120
- Referenced Percent Variables 120
- Procedure Arguments 123
- U, Y, S, and I 123
- Caller Identification 126
- Compatibility Issues 127
- Macro Procedure 128
- Asynchronous Procedures 129
- Condition Block 130
- BlockScript Block 130
- Inputs and Outputs 131
- Environment Variables 132
- Local Variables 132
- Default Phase 134
- Local Variables and Phases 135
- Discrete Semantics 135
- Continuous Semantics 137
- Looping Concepts 137
- Terminology 137
- Loops and Scalar Code 137
- Vectorized Code 139
- Types of Loops 139
- Parameters 141
- Optimizations 143
- Dead Code Elimination 143
- Implicit Type Conversion 144
- Special Directives 144
- UserCode Block 145
- Parameterized UCB Callout 146
- Software Constructs 147
- BREAK Block 148
- CONTINUE Block 148
- Local Variable Block 148
- Continuous Subsystem 149
- Explicit Phases 150
- Integrator 150
- Limitations 150
- Shared Memory Architecture 151
- Shared Memory Callouts 152
- Callout Naming Convention 152
- Mapping Command Options 153
- Definitions and Conventions 153
- From Local Memory 154
- From Shared Memory 154
- option is not used 155
- @offset = offset plus 1@@ 156
- ) data types 158
- Callout Pairs 159
- syntax to call 160
- options 161
- Scalar Gain Block Example 165
- Vectorized Gain Block Example 166
- Array Subscripts 167
- Signal Connectivity 168
- Block Outputs 168
- Block Inputs 168
- AutoCode Reference 6-6 ni.com 169
- Vectorization Modes 170
- Vector Labels and Names 171
- Vectorization Features 177
- Split-Merge Inefficiency 180
- Split Vector 180
- External Outputs 184
- Copy-Back 184
- Eliminating Copy-Back 186
- Other Copy-Back Scenarios 186
- Matrix Outputs 191
- Code Optimization 192
- Chapter 7 Code Optimization 193
- AutoCode Reference 7-2 ni.com 193
- AutoCode Reference 7-4 ni.com 195
- Restart Capability 196
- AutoCode Reference 7-6 ni.com 197
- Merging INIT Sections 199
- -Oreuse 1 202
- Constant Propagation 204
- Optimizing with Matrix Blocks 207
- AutoCode Sim Cdelay Scheduler 211
- Task Posting Policies 212
- Standard AutoCode Scheduler 213
- AutoCode Reference 8-4 ni.com 214
- Scheduler Pipeline 215
- AutoCode Reference 8-6 ni.com 216
- AutoCode Reference 8-8 ni.com 218
- Sim Cdelay Scheduler 219
- Implementation Details 222
- DataStore Priority Problem 223
- Global Scope Signals and 228
- Parameterless Procedures 228
- Data Monitoring/Injection 229
- AutoCode Reference 9-4 ni.com 231
- Parameterless Procedure 232
- Output Specification 233
- Global Output Connection 233
- Issues and Limitations 235
- SystemBuild Simulator 235
- Connection to External Output 236
- Recommendations 236
- Naming Convention 236
- Model Documentation 236
- Explicit Sequencing 236
- Command Options 237
- Technical Support and 238
- Professional Services 238
- AutoCode Reference I-2 ni.com 240
- AutoCode Reference I-4 ni.com 242
- AutoCode Reference I-6 ni.com 244
- AutoCode Reference I-8 ni.com 246
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