ANALOG DEVICES W5.0 Compiler Manual

W 5.0

C/C++ Compiler Manual

for SHARC

Revision 1.5, January 2011

Processors

Part Number

82-001963-02

Analog Devices, Inc. One Technology Way Norwood, Mass. 02062-9106

Printed in the USA.

Disclaimer

Analog Devices, Inc. reserves the right to change this product without prior notice. Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use; nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under the patent rights of Analog Devices, Inc.

Trademark and Service Mark Notice

The Analog Devices logo, SHARC, and VisualDSP++ are registered trademarks of Analog Devices, Inc.

All other brand and product names are trademarks or service marks of their respective owners.

PREFACE

Purpose of This Manual ............................................................. xxxi

Intended Audience ..................................................................... xxxi

Manual Contents ...................................................................... xxxii

What’s New in This Manual ...................................................... xxxii

Technical or Customer Support ................................................ xxxiii

Supported Processors ................................................................ xxxiv

Product Information ................................................................ xxxiv

Analog Devices Web Site .................................................... xxxiv

VisualDSP++ Online Documentation ................................. xxxv

Technical Library CD ......................................................... xxxvi

EngineerZone ..................................................................... xxxvi

Social Networking Web Sites ............................................. xxxvii

Notation Conventions ............................................................. xxxvii

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Contents

COMPILER

C/C++ Compiler Overview ........................................................... 1-3

Compiler Command-Line Interface .............................................. 1-5

Running the Compiler ............................................................ 1-6

Compiler Command-Line Switches ......................................... 1-7

C/C++ Compiler Switch Summaries .................................... 1-7

C/C++ Mode Selection Switch Descriptions ...................... 1-20

-c89 ............................................................................. 1-20

-c99 ............................................................................. 1-20

-c++ ............................................................................. 1-20

C/C++ Compiler Common Switch Descriptions ................ 1-21

sourcefile ...................................................................... 1-21

-@ filename .................................................................. 1-21

-A name[tokens] ........................................................... 1-21

-add-debug-libpaths ...................................................... 1-22

-aligned-stack ............................................................... 1-23

-alttok ......................................................................... 1-23

-always-inline ............................................................... 1-24

-annotate ...................................................................... 1-24

-annotate-loop-instr ...................................................... 1-24

-auto-attrs .................................................................... 1-25

-build-lib ...................................................................... 1-25

-C ................................................................................ 1-25

-c ................................................................................. 1-25

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-compatible-pm-dm ...................................................... 1-25

-const-read-write ........................................................... 1-25

-const-strings ................................................................ 1-26

-D ................................................................................ 1-26

-debug-types ................................................................. 1-26

-double-size[-32|-64] ..................................................... 1-27

-double-size-any ............................................................ 1-28

-dry .............................................................................. 1-28

-dryrun ......................................................................... 1-28

-E ................................................................................. 1-29

-ED .............................................................................. 1-29

-EE ............................................................................... 1-29

-eh ................................................................................ 1-29

-enum-is-int .................................................................. 1-30

-extra-keywords ............................................................. 1-30

-file-attr

name[=value] .................................................. 1-31

-flags ............................................................................. 1-31

-float-to-int ................................................................... 1-32

-force-circbuf ................................................................ 1-32

-fp-associative ............................................................... 1-32

-full-version .................................................................. 1-32

-fx-contract ................................................................... 1-33

-fx-rounding-mode-biased ............................................. 1-33

-fx-rounding-mode-truncation ....................................... 1-33

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-fx-rounding-mode-unbiased ......................................... 1-33

-g ................................................................................. 1-33

-glite ........................................................................... 1-34

-H ............................................................................... 1-34

-HH ............................................................................. 1-35

-h[elp] .......................................................................... 1-35

-I ................................................................................ 1-35

-I- ................................................................................ 1-36

-i .................................................................................. 1-36

-implicit-pointers .......................................................... 1-36

-include ....................................................................... 1-37

-ipa .............................................................................. 1-37

-L ................................................................................ 1-38

-l ................................................................................. 1-38

-list-workarounds .......................................................... 1-39

-M ............................................................................... 1-39

-MD ............................................................................ 1-39

-MM ............................................................................ 1-39

-Mo .............................................................................. 1-40

-Mt .............................................................................. 1-40

-map ............................................................................ 1-40

-mem ........................................................................... 1-40

-multiline ..................................................................... 1-40

-never-inline ................................................................. 1-41

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-no-aligned-stack ........................................................... 1-41

-no-alttok ..................................................................... 1-41

-no-annotate ................................................................. 1-41

-no-annotate-loop-instr ................................................. 1-42

-no-auto-attrs ................................................................ 1-42

-no-builtin .................................................................... 1-42

-no-circbuf .................................................................... 1-43

-no-const-strings ........................................................... 1-43

-no-db .......................................................................... 1-43

-no-defs ........................................................................ 1-43

-no-eh ........................................................................... 1-43

-no-extra-keywords ........................................................ 1-44

-no-fp-associative .......................................................... 1-44

-no-fx-contract .............................................................. 1-44

-no-mem ....................................................................... 1-45

-no-multiline ................................................................ 1-45

-no-progress-rep-timeout ............................................... 1-45

-no-sat-associative ......................................................... 1-45

-no-saturation ............................................................... 1-46

-no-shift-to-add ............................................................ 1-46

-no-simd ....................................................................... 1-46

-no-std-ass .................................................................... 1-47

-no-std-def .................................................................... 1-47

-no-std-inc .................................................................... 1-47

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-no-std-lib .................................................................... 1-47

-no-threads ................................................................... 1-47

-no-workaround ........................................................... 1-48

-normal-word-code ....................................................... 1-48

-nwc ............................................................................. 1-48

-O[0|1] ........................................................................ 1-48

-Oa .............................................................................. 1-49

-Og .............................................................................. 1-49

-Os ............................................................................... 1-49

-Ov .............................................................................. 1-49

-o ................................................................................ 1-51

-overlay ........................................................................ 1-52

-overlay-clobbers .......................................................... 1-52

-P ................................................................................. 1-53

-PP ............................................................................... 1-53

-path-{ asm | compiler | lib | link } ............................... 1-53

-path-install ................................................................. 1-53

-path-output ................................................................ 1-54

-path-temp .................................................................. 1-54

-pch ............................................................................. 1-54

-pchdir ........................................................................ 1-54

-pgo-session ................................................................. 1-54

-pguide ......................................................................... 1-55

-pplist ......................................................................... 1-55

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-proc processor .............................................................. 1-56

-progress-rep-func ......................................................... 1-57

-progress-rep-opt ........................................................... 1-57

-progress-rep-timeout .................................................... 1-57

-progress-rep-timeout-secs secs ...................................... 1-57

-R ................................................................................. 1-57

-R- ............................................................................... 1-58

-reserve ......................................................................... 1-58

-restrict-hardware-loops ................................................. 1-59

-S ................................................................................. 1-59

-s .................................................................................. 1-59

-sat-associative .............................................................. 1-59

-save-temps ................................................................... 1-59

-section ......................................................................... 1-60

-short-word-code ........................................................... 1-61

-show ............................................................................ 1-61

-si-revision .................................................................... 1-61

-signed-bitfield .............................................................. 1-62

-structs-do-not-overlap .................................................. 1-62

-swc .............................................................................. 1-63

-syntax-only .................................................................. 1-63

-sysdefs ......................................................................... 1-63

-T ................................................................................ 1-63

-threads ........................................................................ 1-64

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-time ............................................................................ 1-64

-U ............................................................................... 1-64

-unsigned-bitfield ......................................................... 1-65

-v ................................................................................. 1-65

-verbose ........................................................................ 1-66

-version ........................................................................ 1-66

-W ............................................................................... 1-66

-Werror-limit number ................................................... 1-67

-Werror-warnings ......................................................... 1-67

-Wremarks .................................................................... 1-67

-Wterse ......................................................................... 1-67

-w ................................................................................ 1-67

-warn-protos ................................................................. 1-68

-workaround ................................................................. 1-68

-write-files .................................................................... 1-68

-write-opts .................................................................... 1-69

-xref

filename .............................................................. 1-69

C Mode (MISRA) Compiler Switch Descriptions .............. 1-70

-misra ........................................................................... 1-70

-misra-linkdir ............................................................... 1-70

-misra-no-cross-module ................................................ 1-70

-misra-no-runtime ........................................................ 1-71

-misra-strict .................................................................. 1-71

-misra-suppress-advisory ............................................... 1-71

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-misra-testing ................................................................ 1-71

-Wmis_suppress ............................................................ 1-71

-Wmis_warn ................................................................. 1-72

C++ Mode Compiler Switch Descriptions .......................... 1-72

-anach ........................................................................... 1-72

-check-init-order ........................................................... 1-73

-extern-inline ................................................................ 1-74

-friend-injection ............................................................ 1-74

-full-dependency-inclusion ............................................ 1-74

-ignore-std .................................................................... 1-75

-no-anach ..................................................................... 1-75

-no-extern-inline ........................................................... 1-75

-no-friend-injection ....................................................... 1-76

-no-implicit-inclusion ................................................... 1-76

-no-rtti ......................................................................... 1-76

-no-std-templates .......................................................... 1-76

-rtti .............................................................................. 1-76

-std-templates ............................................................... 1-77

Environment Variables Used by the Compiler ........................ 1-77

Data Type and Data Type Sizes .............................................. 1-78

Integer Data Types ............................................................ 1-80

Floating-Point Data Types ................................................. 1-80

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Optimization Control ........................................................... 1-81

Optimization Levels ......................................................... 1-81

Interprocedural Analysis ................................................... 1-84

Interaction With Libraries ............................................. 1-85

Controlling Silicon Revision and Anomaly Workarounds

Within the Compiler .......................................................... 1-86

Using the -si-revision Switch ............................................. 1-87

Using the -workaround Switch .......................................... 1-88

Using the -no-workaround Switch ..................................... 1-89

Interactions Between the Silicon Revision and

Workaround Switches .................................................... 1-89

Using Native Fixed-Point Types .................................................. 1-90

Fixed-Point Type Support ...................................................... 1-90

Native Fixed-Point Types ....................................................... 1-91

Native Fixed-Point Constants ................................................ 1-92

A Motivating Example .......................................................... 1-93

Fixed-Point Arithmetic Semantics .......................................... 1-94

Data Type Conversions and Fixed-Point Types ....................... 1-94

Bit-Pattern Conversion Functions: bitsfx and fxbits ................ 1-96

Arithmetic Operators for Fixed-Point Types ........................... 1-97

FX_CONTRACT ................................................................. 1-99

Rounding Behavior ............................................................. 1-101

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Arithmetic Library Functions ............................................... 1-103

divifx .............................................................................. 1-104

idivfx .............................................................................. 1-105

fxdivi .............................................................................. 1-106

mulifx ............................................................................. 1-107

absfx ............................................................................... 1-108

roundfx .......................................................................... 1-108

countlsfx ......................................................................... 1-109

strtofxfx .......................................................................... 1-109

Fixed-Point I/O Conversion Specifiers ................................. 1-109

Setting the Rounding Mode ................................................. 1-111

Language Standards Compliance ............................................... 1-113

C Mode .............................................................................. 1-113

C++ Mode ........................................................................... 1-114

MISRA-C Compiler ................................................................. 1-115

MISRA-C Compiler Overview ............................................. 1-115

MISRA-C Compliance ........................................................ 1-116

Using the Compiler to Achieve Compliance ..................... 1-117

Rules Descriptions ............................................................... 1-120

C/C++ Compiler Language Extensions ...................................... 1-128

Function Inlining ................................................................ 1-133

Inlining and Optimization .............................................. 1-136

Inlining and Out-of-Line Copies ..................................... 1-136

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Inlining and Global asm Statements ................................ 1-137

Inlining and Sections ...................................................... 1-137

Variable Argument Macros .................................................. 1-138

Restricted Pointers .............................................................. 1-138

Variable-Length Array Support ............................................ 1-139

Non-Constant Initializer Support ........................................ 1-141

Designated Initializers ......................................................... 1-142

Hexadecimal Floating-Point Numbers ................................. 1-144

Declarations Mixed With Code ........................................... 1-145

Compound Literals ............................................................. 1-146

C++ Style Comments .......................................................... 1-147

Enumeration Constants That Are Not int Type .................... 1-147

Boolean Type Support Keywords (bool, true, false) .............. 1-147

The fract Native Fixed-Point Type ....................................... 1-148

Inline Assembly Language Support Keyword (asm) .............. 1-148

asm() Construct Syntax ................................................... 1-150

asm() Construct Syntax Rules ..................................... 1-152

asm() Construct Template Example ............................. 1-153

Assembly Construct Operand Description ....................... 1-154

Using long long Types in asm Constraints ....................... 1-160

Assembly Constructs With Multiple Instructions ............. 1-161

Assembly Construct Reordering and Optimization .......... 1-162

Assembly Constructs With Input and Output

Operands ..................................................................... 1-163

Assembly Constructs With Compile-Time Constants ...... 1-164

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Assembly Constructs and Flow Control ........................... 1-165

Guidelines on the Use of asm() Statements ...................... 1-165

Dual Memory Support Keywords (pm dm) .......................... 1-166

Memory Keywords and Assignments/

Type Conversions ......................................................... 1-169

Memory Keywords and Function Declarations/

Pointers ....................................................................... 1-170

Memory Keywords and Function Arguments ................... 1-171

Memory Keywords and Macros ....................................... 1-172

Bank Type Qualifiers ........................................................... 1-173

Placement Support Keyword (section) .................................. 1-174

Placement of Compiler-Generated Code and Data ............... 1-175

Long Identifiers ................................................................... 1-176

Preprocessor Generated Warnings ........................................ 1-176

Compiler Built-In Functions ................................................ 1-177

Access to System Registers .............................................. 1-177

Circular Buffer Built-In Functions ................................... 1-180

Circular Buffer Increment of an Index ......................... 1-181

Circular Buffer Increment of a Pointer ......................... 1-181

Compiler Performance Built-In Functions ....................... 1-182

Expected Behavior ....................................................... 1-182

Known Values ............................................................. 1-184

Fractional Built-In Functions .......................................... 1-185

Miscellaneous Built-In Function ...................................... 1-187

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Pragmas .............................................................................. 1-187

Data Alignment Pragmas ................................................ 1-189

#pragma align num ..................................................... 1-189

#pragma alignment_region (alignopt) .......................... 1-191

#pragma pack (alignopt) .............................................. 1-192

#pragma pad (alignopt) ............................................... 1-193

Interrupt Handler Pragmas ............................................. 1-193

#pragma implicit_push_sts_handler ............................ 1-194

#pragma interrupt ...................................................... 1-194

#pragma interrupt_complete_nesting .......................... 1-195

#pragma interrupt_complete ....................................... 1-196

#pragma save_restore_40_bits ..................................... 1-196

#pragma save_restore_simd_40_bits

(SIMD SHARCs Only) ............................................ 1-197

Interrupt Pragmas and the Interrupt Vector Table ........ 1-197

Loop Optimization Pragmas ........................................... 1-198

#pragma SIMD_for .................................................... 1-199

#pragma all_aligned .................................................... 1-199

#pragma no_vectorization ........................................... 1-199

#pragma loop_count (min, max, modulo) .................... 1-200

#pragma loop_unroll N .............................................. 1-200

#pragma no_alias ........................................................ 1-203

#pragma vector_for .................................................... 1-203

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General Optimization Pragmas ........................................ 1-204

Function Side-Effect Pragmas .......................................... 1-205

#pragma alloc .............................................................. 1-206

#pragma const ............................................................. 1-206

#pragma misra_func(arg) ............................................. 1-207

#pragma noreturn ....................................................... 1-207

#pragma pgo_ignore .................................................... 1-207

#pragma pure .............................................................. 1-208

#pragma regs_clobbered string .................................... 1-209

#pragma regs_clobbered_call string .............................. 1-213

#pragma overlay .......................................................... 1-217

#pragma result_alignment (n) ...................................... 1-217

Class Conversion Optimization Pragmas .......................... 1-218

#pragma param_never_null param_name [ ... ] ............ 1-218

#pragma suppress_null_check ...................................... 1-219

Template Instantiation Pragmas ...................................... 1-221

#pragma instantiate instance ........................................ 1-222

#pragma do_not_instantiate instance ........................... 1-223

#pragma can_instantiate instance ................................. 1-223

Header File Control Pragmas ........................................... 1-223

#pragma hdrstop ......................................................... 1-223

#pragma no_implicit_inclusion ................................... 1-224

#pragma no_pch ......................................................... 1-225

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Fixed-Point Arithmetic Pragmas ...................................... 1-226

Inline Control Pragmas ................................................... 1-229

#pragma once ............................................................. 1-226

#pragma system_header .............................................. 1-226

#pragma FX_CONTRACT {ON|OFF} ....................... 1-227

#pragma FX_ROUNDING_MODE

{TRUNCATION|BIASED|UNBIASED} ................. 1-227

#pragma STDC FX_FULL_PRECISION

{ON|OFF|DEFAULT} ............................................. 1-228

#pragma STDC FX_FRACT_OVERFLOW

{SAT|DEFAULT} ..................................................... 1-228

#pragma always_inline ................................................ 1-229

#pragma inline ........................................................... 1-230

#pragma never_inline ................................................. 1-230

Linking Control Pragmas ................................................ 1-231

#pragma linkage_name identifier ................................. 1-231

#pragma core .............................................................. 1-231

#pragma retain_name ................................................ 1-236

#pragma section/#pragma default_section ................... 1-238

#pragma file_attr(“name[=value]”

[, “name[=value]” [...]]) ............................................ 1-242

#pragma weak_entry .................................................. 1-243

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Diagnostic Control Pragmas ............................................ 1-243

Modifying the Severity of Specific Diagnostics ............. 1-244

Modifying the Behavior of an Entire Class of

Diagnostics .............................................................. 1-245

Saving or Restoring the Current Behavior of All

Diagnostics .............................................................. 1-245

Memory Bank Pragmas ................................................... 1-246

#pragma code_bank(bankname) ................................... 1-247

#pragma data_bank(bankname) ................................... 1-247

#pragma stack_bank(bankname) .................................. 1-248

#pragma bank_memory_kind(bankname, kind) ............ 1-250

#pragma bank_read_cycles(bankname, cycles) ............... 1-250

#pragma bank_write_cycles(bankname, cycles) .............. 1-251

#pragma bank_optimal_width(bankname, width) ......... 1-252

Code Generation Pragmas ............................................... 1-253

#pragma avoid_anomaly_45 {on | off} ......................... 1-253

#pragma no_db_return ................................................ 1-253

Exceptions Table Pragma ................................................. 1-254

#pragma generate_exceptions_tables ............................ 1-254

GCC Compatibility Extensions ........................................... 1-256

Statement Expressions ..................................................... 1-256

Type Reference Support Keyword (Typeof) ...................... 1-258

GCC Generalized Lvalues ............................................... 1-259

Conditional Expressions with Missing Operands .............. 1-259

Zero-Length Arrays ......................................................... 1-260

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GCC Variable Argument Macros ..................................... 1-260

Line Breaks in String Literals .......................................... 1-260

Arithmetic on Pointers to Void and Pointers to

Cast to Union ................................................................. 1-261

Ranges in Case Labels ..................................................... 1-261

Escape Character Constant ............................................. 1-261

Alignment Inquiry Keyword (__alignof__) ...................... 1-261

Keyword for Specifying Names in Generated

Function, Variable and Type Attribute Keyword

Unnamed struct/union Fields Within struct/unions ......... 1-263

Functions .................................................................... 1-261

Assembler (asm) ........................................................... 1-262

(__attribute__) ............................................................ 1-263

C++ Fractional Type Support .............................................. 1-264

Format of Fractional Literals ........................................... 1-264

Conversions Involving Fractional Values .......................... 1-265

Fractional Arithmetic Operations .................................... 1-265

Mixed Mode Operations ................................................. 1-266

Saturated Arithmetic ........................................................... 1-266

Support for 40-bit Arithmetic ............................................. 1-267

Using 40-bit Arithmetic in Compiled Code ..................... 1-268

Run-Time Library Functions That Use 40-bit

Arithmetic ................................................................... 1-269

Interrupt Support ........................................................... 1-270

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SIMD Support .................................................................... 1-271

A Brief Introduction to SIMD Mode ............................... 1-271

What the Compiler Can Do Automatically ...................... 1-272

What Prevents the Compiler From Automatically

Exploiting SIMD Mode ................................................ 1-273

How to Help the Compiler Exploit SIMD Mode ............. 1-274

How to Prevent SIMD Code Generation ......................... 1-275

Accessing External Memory on ADSP-2126x and

ADSP-2136x Processors .................................................... 1-275

Link-Time Checking of Data Placement .......................... 1-275

Inline Functions for External Memory Access .................. 1-276

Support for Interrupts ......................................................... 1-276

Interrupt Dispatchers ...................................................... 1-277

Interrupts and Circular Buffering .................................... 1-281

Avoiding Self-Modifying Code ........................................ 1-281

Interrupt Nesting Restrictions on ADSP-211xx/212xx/

213xx/214xx Processors ................................................ 1-282

Restriction on Use of Super-Fast Dispatcher on

ADSP-2106x Processors ............................................... 1-282

Restrictions on Using Normal and Circular Buffer

Interrupt Dispatchers on ADSP-2136x Processors ......... 1-284

Migrating .ldf Files From Previous VisualDSP++

Installations ...................................................................... 1-284

C++ Support Tables (ctor, gdt) ........................................ 1-285

ADSP-21375 Memory Map ............................................ 1-287

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C++ Run-Time Libraries Rationalization ......................... 1-288

Fixed-Point I/O Support ................................................. 1-288

Preprocessor Features ................................................................ 1-289

Predefined Preprocessor Macros ........................................... 1-290

Writing Macros ................................................................... 1-297

Compound Macros ......................................................... 1-297

C/C++ Run-Time Model and Environment ............................... 1-300

C/C++ Run-Time Environment ........................................... 1-300

Memory Usage ............................................................... 1-302

Program Memory Code Storage .................................. 1-304

Data Memory Data Storage ......................................... 1-305

Program Memory Data Storage ................................... 1-305

Run-Time Stack Storage ............................................. 1-306

Run-Time Heap Storage ............................................ 1-306

Initialization Data Storage ......................................... 1-307

Run-Time Header Storage ........................................... 1-308

Memory Allocation for Stack and Heap on ADSP-2106x,

ADSP-2116x, and ADSP-2126x Processors .................. 1-310

Example of Heap/Stack Memory Allocation ................ 1-311

Measuring the Performance of the Compiler .................... 1-312

Constructors and Destructors of Global Class Instances ....... 1-313

Constructors, Destructors and Memory Placement .......... 1-314

Support for argv/argc .......................................................... 1-315

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Using Multiple Heaps .......................................................... 1-316

Declaring a Heap ............................................................ 1-317

Heap Identifiers .............................................................. 1-319

Allocating C++ STL Objects to a Non-Default Heap ....... 1-319

Using Alternate Heaps With the Standard Interface ......... 1-322

Using the Alternate Heap Interface .................................. 1-323

C++ Run-Time Support for the Alternate Heap

Interface ................................................................... 1-324

Example C Programs ....................................................... 1-325

Compiler Registers ............................................................. 1-327

Miscellaneous Information About Registers ..................... 1-327

User Registers ................................................................. 1-328

Call Preserved Registers ................................................... 1-329

Scratch Registers ............................................................. 1-330

Stack Registers ................................................................ 1-331

Alternate Registers ......................................................... 1-331

Managing the Stack ......................................................... 1-332

Transferring Function Arguments and Return Value ......... 1-338

Passing a C++ Class Instance ........................................... 1-341

Using Data Storage Formats ............................................ 1-341

fract Data Representation ................................................ 1-344

Using the Run-Time Header ........................................... 1-346

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C/C++ and Assembly Interface .................................................. 1-347

Calling Assembly Subroutines From C/C++ Programs .......... 1-347

Calling C/C++ Functions From Assembly Programs ............. 1-350

Using Mixed C/C++ and Assembly Support Macros ......... 1-353

entry .......................................................................... 1-353

exit ............................................................................. 1-353

leaf_entry ................................................................... 1-354

leaf_exit ..................................................................... 1-354

ccall(x) ....................................................................... 1-354

reads(x) ...................................................................... 1-354

puts=x ........................................................................ 1-354

gets(x) ........................................................................ 1-354

alter(x) ....................................................................... 1-355

save_reg ...................................................................... 1-355

restore_reg .................................................................. 1-355

Using Mixed C/C++ and Assembly Naming

Conventions ................................................................ 1-357

Implementing C++ Member Functions in Assembly

Language ..................................................................... 1-359

Writing C/C++ Callable SIMD Subroutines .................... 1-361

C++ Programming Examples ............................................... 1-362

Using Fract Support ........................................................ 1-363

Using Complex Support ................................................. 1-364

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Mixed C/C++/Assembly Programming Examples .................. 1-365

Using Inline Assembly (Add) ........................................... 1-367

Using Macros to Manage the Stack .................................. 1-367

Using Scratch Registers (Dot Product) ............................. 1-369

Using Void Functions (Delay) ......................................... 1-370

Using the Stack for Arguments (Add 5) ........................... 1-372

Using Registers for Arguments and Return (Add 2) .......... 1-373

Using Non-Leaf Routines That Make Calls (RMS) .......... 1-374

Using Call Preserved Registers (Pass Array) ...................... 1-376

Exceptions Tables in Assembly Routines ............................... 1-378

Compiler C++ Template Support ............................................... 1-381

Template Instantiation ......................................................... 1-381

Implicit Instantiation ...................................................... 1-382

Exported Templates ......................................................... 1-383

Generated Template Files ................................................ 1-384

Identifying Un-Instantiated Templates ............................. 1-385

File Attributes ........................................................................... 1-387

Automatically-Applied Attributes ......................................... 1-388

Content Attributes .......................................................... 1-389

FuncName Attributes ...................................................... 1-389

Encoding Attributes ........................................................ 1-390

Default LDF Placement ....................................................... 1-390

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Sections Versus Attributes ................................................... 1-391

Granularity ..................................................................... 1-391

“Hard” Versus “Soft” ...................................................... 1-392

Number of Values ........................................................... 1-392

Using Attributes .................................................................. 1-393

Example 1 ...................................................................... 1-393

Example 2 ...................................................................... 1-395

ACHIEVING OPTIMAL PERFORMANCE FROM C/C++

SOURCE CODE

General Guidelines ....................................................................... 2-2

How the Compiler Can Help .................................................. 2-3

Using the Compiler Optimizer ............................................ 2-4

Using Compiler Diagnostics ............................................... 2-4

Warnings and Remarks ................................................... 2-5

Assembly Annotations ..................................................... 2-7

Using the Statistical Profiler ................................................ 2-7

Using Profile-Guided Optimization .................................... 2-8

Using Profile-Guided Optimization With a Simulator ..... 2-8

Using Profile-Guided Optimization With

Non-Simulatable Applications .................................... 2-10

Profile-Guided Optimization and Multiple

Source Uses ............................................................... 2-10

Profile-Guided Optimization and the -Ov Switch .......... 2-11

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Profile-Guided Optimization and Multiple PGO

Data Sets .................................................................... 2-11

When to Use Profile-Guided Optimization .................... 2-12

Using Interprocedural Optimization .................................. 2-12

Data Types ............................................................................ 2-13

Avoiding Emulated Arithmetic .......................................... 2-14

Getting the Most From IPA ................................................... 2-15

Initialize Constants Statically ............................................. 2-16

Dual Word-Aligning Your Data ......................................... 2-17

Using __builtin_aligned .................................................... 2-18

Avoiding Aliases ................................................................ 2-20

Indexed Arrays Versus Pointers ............................................... 2-22

Trying Pointer and Indexed Styles ...................................... 2-23

Using Function Inlining ....................................................... 2-23

Using Inline asm Statements .................................................. 2-24

Memory Usage ...................................................................... 2-25

Improving Conditional Code ...................................................... 2-27

Loop Guidelines ......................................................................... 2-28

Keeping Loops Short ............................................................. 2-28

Avoiding Unrolling Loops ...................................................... 2-29

Avoiding Loop-Carried Dependencies .................................... 2-29

Avoiding Loop Rotation by Hand .......................................... 2-30

Avoiding Complex Array Indexing ......................................... 2-32

Inner Loops vs. Outer Loops .................................................. 2-32

Avoiding Conditional Code in Loops ..................................... 2-33

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Avoiding Placing Function Calls in Loops .............................. 2-34

Avoiding Non-Unit Strides .................................................... 2-34

Loop Control ........................................................................ 2-35

Using the Restrict Qualifier ................................................... 2-36

Avoiding Long Latencies ....................................................... 2-37

Using Built-In Functions in Code Optimization .......................... 2-38

Using System Support Built-In Functions .............................. 2-38

Using Circular Buffers ........................................................... 2-40

Smaller Applications: Optimizing for Code Size .......................... 2-42

Using Pragmas for Optimization ................................................. 2-43

Function Pragmas ................................................................. 2-44

#pragma alloc ................................................................... 2-44

#pragma const .................................................................. 2-45

#pragma pure ................................................................... 2-45

#pragma result_alignment ................................................. 2-45

#pragma regs_clobbered .................................................... 2-46

#pragma optimize_

{off|for_speed|for_space|as_cmd_line} ............................ 2-48

Loop Optimization Pragmas .................................................. 2-49

#pragma loop_count ......................................................... 2-49

#pragma no_vectorization ................................................. 2-50

#pragma vector_for ........................................................... 2-50

#pragma SIMD_for .......................................................... 2-51

#pragma all_aligned .......................................................... 2-51

#pragma no_alias .............................................................. 2-52

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Useful Optimization Switches ...................................................... 2-53

How Loop Optimization Works .................................................. 2-54

Terminology .......................................................................... 2-54

Clobbered Register ............................................................ 2-54

Live Register ..................................................................... 2-55

Spill .................................................................................. 2-55

Scheduling ........................................................................ 2-55

Loop Kernel ...................................................................... 2-56

Loop Prolog ...................................................................... 2-56

Loop Epilog ...................................................................... 2-56

Loop Invariant .................................................................. 2-56

Hoisting ........................................................................... 2-57

Sinking ............................................................................. 2-57

Loop Optimization Concepts ................................................. 2-57

Software Pipelining ........................................................... 2-58

Loop Rotation .................................................................. 2-59

Loop Vectorization ............................................................ 2-61

Modulo Scheduling ........................................................... 2-63

Initiation Interval (II) and the Kernel ............................ 2-65

Minimum Initiation Interval Due to Resources

(Res MII) ................................................................... 2-68

Minimum Initiation Interval Due to Recurrences

(Rec MII) ................................................................... 2-68

Stage Count (SC) .......................................................... 2-69

VisualDSP++ 5.0 C/C++ Compiler Manual xxix for SHARC Processors

Variable Expansion and MVE Unroll ............................. 2-71

Trip Count ................................................................... 2-76

A Worked Example ............................................................... 2-77

Assembly Optimizer Annotations ................................................ 2-80

Global Information ............................................................... 2-81

Procedure Statistics ............................................................... 2-83

Instruction Annotations ........................................................ 2-88

Loop Identification ............................................................... 2-88

Loop Identification Annotations ....................................... 2-89

File Position ..................................................................... 2-93

Vectorization ......................................................................... 2-96

Loop Flattening ................................................................ 2-97

Vectorization Annotations ................................................. 2-99

Modulo Scheduling Information ......................................... 2-101

Annotations for Modulo Scheduled Instructions .............. 2-101

Warnings, Failure Messages and Advice ................................ 2-107

Analyzing Your Application ....................................................... 2-111

Stack Overflow Detection ................................................... 2-111

The Stack Overflow Detection Facility ............................ 2-113

INDEX

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