Global Symbol Usage | HP UX Developer Tools guide

HP-UX Architecture Conventions

Compiler Conventions

possible to declare a procedure that cannot conﬂict with HP Pascal/HP-UX procedure names by using uppercase letters. However, there is an aliasing mechanism in some compilers that allows you to declare a case-sensitive name for external use. See the appropriate language reference manual for more information.

Conversely, the .IMPORT directive allows you to reference a procedure name that is exported from another module, either from the Assembler or the compiler. Once a procedure name has been imported, it can be referenced exactly as if it were declared in the same module.

Data symbols can be exported and imported just like procedure names. However, not all compilers export the names of global variables, or provide a mechanism to reference data symbols exported from an assembly language module. For example, the HP Pascal/HP-UX compiler does not normally do this, while the HP C/HP-UX compiler does. HP FORTRAN 77/HP-UX named common blocks are exported, but the names of the variables within the common blocks are not.

It was mentioned before that data is allocated beginning from a virtual space offset 0x40000000. For convenience as well as compatibility with future releases of HP-UX systems, all data in the $PRIVATE$ space must be accessed relative to general register 27, called %dp. EStandard run-time start-up code, from the ﬁle /usr/ccs/lib/crt0.o, must be linked with every program. This start-up code declares a global symbol called $global$ in the $GLOBAL$ subspace. This code also loads the address of this symbol into the %dp register before beginning program execution. This register must not be changed during the execution of a program. Since the %dp register is known to contain the address of $global$, the following single instruction does the load as long as the displacement from $global$ to the desired location is less than 8 kilobytes:

LDW var-$global$(%dp),%r3

If the desired location is not known to be close enough to $global$, use the following sequence:

Global Symbol Usage

ADDIL	L'var-$global$,%dp	;result in r1
LDW	R'var-$global$(%r1),%r3

Chapter 3

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HP UX Developer Tools manual Global Symbol Usage

Contents

92432-90012 June HP 9000 Computers Restricted Rights Legend Legal NoticesHanover Street Palo Alto, California Contents Assembler Directives and Pseudo-Operations Contents Contents Contents Contents Pseudo-Instruction Set Assembling Your Program Programming Examples Diagnostic MessagesIndex Printing History PrefaceEdition Date Software Version Related Documentation Audience This Manual Typographical Conventions Summary of Technical Changes for HP-UX Assembler Features Assembly Language Assembler Features Summary of Changes for PA-RISC 2.0W Wide Mode, 64-bit Summary of Changes for PA-RISCSummary of Changes for PA-RISC Chapter Summary of Changes for PA-RISC 2.0W Wide Mode, 64-bit Program Structure Label Opcode Operands Comments Program Structure Symbols and Constants Symbols and Constants Integer Constants Signed Unsigned Registers and Register Mnemonics Registers and Register Mnemonics Registers by using an L or R sufﬁx General Registers Single-Precision Floating-Point Registers Space Registers Double-Precision Floating-Point RegistersControl Registers Synonyms Register Synonyms Description Register Procedure Calling Conventions Expressions ExpressionsStandard Arithmetic Operators Operator Operation Legal Combinations For Relocatable Terms Operation Result Available Field Selectors Meaning Field Meaning Selector Multiple of 2048 allows a three-instruction sequence Parenthesized Subexpressions Operands and Completers Operands and Completers Addi Deﬁning New Instructions With Macros Macro ProcessingMacro Processing Contains general register 19, or binary 10011. These Spaces HP-UX Architecture Conventions Spaces Memory Layout on HP-UX Sr4 Sr5 Sr6 Attributes SubspacesSubspaces Standard Subspaces and Sort Keys DirectivesSpace Subspace Sort Key Use Sections in 64-bit Mode Sections in 64-bit Mode $INIT$ Location Counters Location Counters Compiler Conventions Compiler Conventions Compiler Conventions Global Symbol Usage Mfctl Shared Libraries Assembly ListingShared Libraries Assembly Listing Assembler Directives IntroductionDirective Function Requests common storage for a speciﬁed number Bytes Pseudo-Operations Directive Function Reserves 16 bits a half word of storage Syntax Align DirectiveParameters Example Discussion Allow DirectiveAllow Directive To the .LEVEL speciﬁed for the ﬁle Block and .BLOCKZ Pseudo-Operations Block and .BLOCKZ Pseudo-Operations Space $TEXT$ Subspa $CODE$ Block Byte Pseudo-Operation Byte Pseudo-OperationByte initvalue , initvalue Call Directive Call DirectiveCall argumentdescription argumentdescription Return value for a procedure Form of argument-description is Arg=location Where arg canﬁrst word in the argument list Second word in the argument list LIT Align Word Procend Export Callinfo Directive Callinfo DirectiveCallinfo parameter , parameter Register ENTRYSR= Unwound It restores the RP value when it encounters a .LEAVE Callinfo Directive Stack Frames Re-enter code subspace Comm Directive Comm DirectiveLabel .COMM numbytes Label Labels the location of the reserved storage Copyright Directive Copyright DirectiveCompany-name Proc Callinfo Enter Fraction E power Integer .fraction E powerDouble Pseudo-Operation Double Pseudo-Operation Dword Pseudo-Operation Dword Pseudo-OperationDword initvalue , initvalue END Directive END Directive Endm Directive Endm Directive Enter and .LEAVE Pseudo-Operations Enter and .LEAVE Pseudo-Operations Space $TEXT$ Entry and .EXIT Directives Entry and .EXIT Directives EQU Directive Symbolicname .EQU valueEQU Directive Value Export Directive Export Directive Argument Export proc,ENTRY,ARGW0=GR Float Pseudo-Operation Float Pseudo-Operation Half Pseudo-Operation Half Pseudo-OperationHalf initvalue , initvalue Import Directive Import Directive NOP END Label Directive Label DirectiveLabel labelid Labelid Names the label identiﬁer Level Directive Level Directive Level Directive Listoff and .LISTON Directives Listoff and .LISTON Directives Liston Code Space $TEXT$ SPNUM=0,SORT=0 Subspa $CODE$ Locct Directive Locct Directive Macro Directive Macro DirectiveLabel .MACRO formalparameter,formalparameter Examples 100 Origin Directive Origin DirectiveChapter 101 Proc and .PROCEND Directives Proc and .PROCEND Directives102 Chapter 103 REG Directive REG DirectiveLabel .REG typedregister Label User-deﬁned register name Shlibversion Directive Shlibversion DirectiveChapter 105 Space Directive Space Directive106 Chapter 107 Spnum Pseudo-Operation Spnum Pseudo-Operation108 String and .STRINGZ Pseudo-Operations String and .STRINGZ Pseudo-OperationsChapter 109 110 Subspa Directive Subspa DirectiveName An identiﬁer that names the current subspace Chapter 111 112 Chapter 113 Version Directive Version Directive114 Word Pseudo-Operation Word Pseudo-OperationWord initvalue , initvalue Chapter 115 Programming Aids Directive Space Name Default ParametersProgramming Aids Predeﬁned Subspace Directives Chapter 117 Shortdata Programming Aids 118 119 Pseudo-Instruction Set 120 Cond Description Compare and Branch Conditions Comb and ComibChapter 121 122 Add and Branch Conditions Addb and Addib Description 123 Invoking the Assembler Using the as Command Using the as CommandAssemble code for the architecture 124 Level ﬁlenameChapter 125 Tables, see HP-UX Linker and Libraries WnumberOnline User Guide 126 Using the cc Command Using the cc CommandPassing Arguments to the Assembler Wa, ,as-argument as-argument 128 Cpp Preprocessor 129 Programming Examples Binary Search for Highest Bit Position Binary Search for Highest Bit Position130 Chapter 131 Copying a String Copying a String132 Chapter 133 Dividing a Double-Word Dividend Dividing a Double-Word Dividend134 Chapter 135 Programming Examples Demonstrating the Procedure Calling Convention Demonstrating the Procedure Calling ConventionProgram Listing 136 Chapter 137 Assembly Program Listing Assembly Program Listing From the C Compiler Output of the cc -S CommandOutput of the cc -S Command 138 Chapter 139 Output of the cc -S Command 140 141 142 Option operand Chapter 143 144 Reserve Use a general register Wrong register type usedChapter 145 Use a control register Use a space register146 Chapter 147 148 Chapter 149 150 Chapter 151 152 Used to invoke the assembler Chapter 153 Error Messages Error Messages154 Chapter 155 156 Chapter 157 158 1028 10271029 1030 1032 10311033 1034 1036 10351037 1038 162 Chapter 163 1055 10541056 1057 Chapter 165 166 Chapter 167 168 1080 Format keyword=value1081 1082 170 1089 10881090 Chapter 171 1094 10911095 1096 1098 10971099 1100 1102 11011103 1104 Chapter 175 1105 Panic Messages Panic Messages176 2006 20052007 2008 User Warning Messages User Warning Messages178 7004 70037005 7006 180 Chapter 181 182 Limit Error Messages Limit Error Messages7200 7201 7203 72027204 184 Chapter 185 Diagnostic Messages 186 Branching Error Messages Branching Error MessagesChapter 187 188 Chapter 189 190 Chapter 191 192 7828 78277834 7835 7837 7836Expr 194 Index 195 Index Numerics 196 Copyright Index 197 HP C/HP-UX,49 198 Mfctl Index 199 Double 200 See also memory Index 201 202