1 @c Copyright (C) 2000-2014 Free Software Foundation, Inc. 2 @c This is part of the GAS manual. 3 @c For copying conditions, see the file as.texinfo. 4 @ifset GENERIC 5 @page 6 @node ESA/390-Dependent 7 @chapter ESA/390 Dependent Features 8 @end ifset 9 @ifclear GENERIC 10 @node Machine Dependencies 11 @chapter ESA/390 Dependent Features 12 @end ifclear 13 14 @cindex i370 support 15 @cindex ESA/390 support 16 17 @menu 18 * ESA/390 Notes:: Notes 19 * ESA/390 Options:: Options 20 * ESA/390 Syntax:: Syntax 21 * ESA/390 Floating Point:: Floating Point 22 * ESA/390 Directives:: ESA/390 Machine Directives 23 * ESA/390 Opcodes:: Opcodes 24 @end menu 25 26 @node ESA/390 Notes 27 @section Notes 28 The ESA/390 @code{@value{AS}} port is currently intended to be a back-end 29 for the @sc{gnu} @sc{cc} compiler. It is not HLASM compatible, although 30 it does support a subset of some of the HLASM directives. The only 31 supported binary file format is ELF; none of the usual MVS/VM/OE/USS 32 object file formats, such as ESD or XSD, are supported. 33 34 When used with the @sc{gnu} @sc{cc} compiler, the ESA/390 @code{@value{AS}} 35 will produce correct, fully relocated, functional binaries, and has been 36 used to compile and execute large projects. However, many aspects should 37 still be considered experimental; these include shared library support, 38 dynamically loadable objects, and any relocation other than the 31-bit 39 relocation. 40 41 @node ESA/390 Options 42 @section Options 43 @code{@value{AS}} has no machine-dependent command-line options for the ESA/390. 44 45 @cindex ESA/390 Syntax 46 @node ESA/390 Syntax 47 @section Syntax 48 The opcode/operand syntax follows the ESA/390 Principles of Operation 49 manual; assembler directives and general syntax are loosely based on the 50 prevailing AT&T/SVR4/ELF/Solaris style notation. HLASM-style directives 51 are @emph{not} supported for the most part, with the exception of those 52 described herein. 53 54 A leading dot in front of directives is optional, and the case of 55 directives is ignored; thus for example, .using and USING have the same 56 effect. 57 58 A colon may immediately follow a label definition. This is 59 simply for compatibility with how most assembly language programmers 60 write code. 61 62 @samp{#} is the line comment character. 63 64 @samp{;} can be used instead of a newline to separate statements. 65 66 Since @samp{$} has no special meaning, you may use it in symbol names. 67 68 Registers can be given the symbolic names r0..r15, fp0, fp2, fp4, fp6. 69 By using thesse symbolic names, @code{@value{AS}} can detect simple 70 syntax errors. The name rarg or r.arg is a synonym for r11, rtca or r.tca 71 for r12, sp, r.sp, dsa r.dsa for r13, lr or r.lr for r14, rbase or r.base 72 for r3 and rpgt or r.pgt for r4. 73 74 @samp{*} is the current location counter. Unlike @samp{.} it is always 75 relative to the last USING directive. Note that this means that 76 expressions cannot use multiplication, as any occurrence of @samp{*} 77 will be interpreted as a location counter. 78 79 All labels are relative to the last USING. Thus, branches to a label 80 always imply the use of base+displacement. 81 82 Many of the usual forms of address constants / address literals 83 are supported. Thus, 84 @example 85 .using *,r3 86 L r15,=A(some_routine) 87 LM r6,r7,=V(some_longlong_extern) 88 A r1,=F'12' 89 AH r0,=H'42' 90 ME r6,=E'3.1416' 91 MD r6,=D'3.14159265358979' 92 O r6,=XL4'cacad0d0' 93 .ltorg 94 @end example 95 should all behave as expected: that is, an entry in the literal 96 pool will be created (or reused if it already exists), and the 97 instruction operands will be the displacement into the literal pool 98 using the current base register (as last declared with the @code{.using} 99 directive). 100 101 @node ESA/390 Floating Point 102 @section Floating Point 103 @cindex floating point, ESA/390 (@sc{ieee}) 104 @cindex ESA/390 floating point (@sc{ieee}) 105 The assembler generates only @sc{ieee} floating-point numbers. The older 106 floating point formats are not supported. 107 108 109 @node ESA/390 Directives 110 @section ESA/390 Assembler Directives 111 112 @code{@value{AS}} for the ESA/390 supports all of the standard ELF/SVR4 113 assembler directives that are documented in the main part of this 114 documentation. Several additional directives are supported in order 115 to implement the ESA/390 addressing model. The most important of these 116 are @code{.using} and @code{.ltorg} 117 118 @cindex ESA/390-only directives 119 These are the additional directives in @code{@value{AS}} for the ESA/390: 120 121 @table @code 122 @item .dc 123 A small subset of the usual DC directive is supported. 124 125 @item .drop @var{regno} 126 Stop using @var{regno} as the base register. The @var{regno} must 127 have been previously declared with a @code{.using} directive in the 128 same section as the current section. 129 130 @item .ebcdic @var{string} 131 Emit the EBCDIC equivalent of the indicated string. The emitted string 132 will be null terminated. Note that the directives @code{.string} etc. emit 133 ascii strings by default. 134 135 @item EQU 136 The standard HLASM-style EQU directive is not supported; however, the 137 standard @code{@value{AS}} directive .equ can be used to the same effect. 138 139 @item .ltorg 140 Dump the literal pool accumulated so far; begin a new literal pool. 141 The literal pool will be written in the current section; in order to 142 generate correct assembly, a @code{.using} must have been previously 143 specified in the same section. 144 145 @item .using @var{expr},@var{regno} 146 Use @var{regno} as the base register for all subsequent RX, RS, and SS form 147 instructions. The @var{expr} will be evaluated to obtain the base address; 148 usually, @var{expr} will merely be @samp{*}. 149 150 This assembler allows two @code{.using} directives to be simultaneously 151 outstanding, one in the @code{.text} section, and one in another section 152 (typically, the @code{.data} section). This feature allows 153 dynamically loaded objects to be implemented in a relatively 154 straightforward way. A @code{.using} directive must always be specified 155 in the @code{.text} section; this will specify the base register that 156 will be used for branches in the @code{.text} section. A second 157 @code{.using} may be specified in another section; this will specify 158 the base register that is used for non-label address literals. 159 When a second @code{.using} is specified, then the subsequent 160 @code{.ltorg} must be put in the same section; otherwise an error will 161 result. 162 163 Thus, for example, the following code uses @code{r3} to address branch 164 targets and @code{r4} to address the literal pool, which has been written 165 to the @code{.data} section. The is, the constants @code{=A(some_routine)}, 166 @code{=H'42'} and @code{=E'3.1416'} will all appear in the @code{.data} 167 section. 168 169 @example 170 .data 171 .using LITPOOL,r4 172 .text 173 BASR r3,0 174 .using *,r3 175 B START 176 .long LITPOOL 177 START: 178 L r4,4(,r3) 179 L r15,=A(some_routine) 180 LTR r15,r15 181 BNE LABEL 182 AH r0,=H'42' 183 LABEL: 184 ME r6,=E'3.1416' 185 .data 186 LITPOOL: 187 .ltorg 188 @end example 189 190 191 Note that this dual-@code{.using} directive semantics extends 192 and is not compatible with HLASM semantics. Note that this assembler 193 directive does not support the full range of HLASM semantics. 194 195 @end table 196 197 @node ESA/390 Opcodes 198 @section Opcodes 199 For detailed information on the ESA/390 machine instruction set, see 200 @cite{ESA/390 Principles of Operation} (IBM Publication Number DZ9AR004). 201
