| 1 | @c Copyright 2000, 2002 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). |