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diff --git a/gas/doc/c-or1k.texi b/gas/doc/c-or1k.texi new file mode 100644 index 0000000..0260fb1 --- /dev/null +++ b/gas/doc/c-or1k.texi @@ -0,0 +1,300 @@ +@c Copyright (C) 1991-2018 Free Software Foundation, Inc. +@c This is part of the GAS manual. +@c For copying conditions, see the file as.texinfo. +@ifset GENERIC +@page +@node OpenRISC-Dependent +@chapter OPENRISC Dependent Features +@end ifset +@ifclear GENERIC +@node Machine Dependencies +@chapter OPENRISC Dependent Features +@end ifclear + +@cindex OPENRISC support +@menu +* OpenRISC-Syntax:: Syntax +* OpenRISC-Float:: Floating Point +* OpenRISC-Directives:: OpenRISC Machine Directives +* OpenRISC-Opcodes:: Opcodes +@end menu + +@cindex OPENRISC syntax +@cindex syntax, OPENRISC +@node OpenRISC-Syntax +@section OpenRISC Syntax +The assembler syntax follows the OpenRISC 1000 Architecture Manual. + +@menu +* OpenRISC-Chars:: Special Characters +* OpenRISC-Regs:: Register Names +* OpenRISC-Relocs:: Relocations +@end menu + +@node OpenRISC-Chars +@subsection Special Characters + +@cindex line comment character, OpenRISC +@cindex OpenRISC line comment character +A @samp{#} character appearing anywhere on a line indicates the start +of a comment that extends to the end of that line. + +@cindex line separator, OpenRISC +@cindex statement separator, OpenRISC +@cindex OpenRISC line separator +@samp{;} can be used instead of a newline to separate statements. + +@node OpenRISC-Regs +@subsection Register Names +@cindex OpenRISC registers +@cindex register names, OpenRISC + +The OpenRISC register file contains 32 general pupose registers. + +@itemize @bullet +@item +The 32 general purpose registers are referred to as @samp{r@var{n}}. + +@item +The stack pointer register @samp{r1} can be referenced using the alias +@samp{sp}. + +@item +The frame pointer register @samp{r2} can be referenced using the alias +@samp{fp}. + +@item +The link register @samp{r9} can be referenced using the alias @samp{lr}. +@end itemize + +Floating point operations use the same general purpose registers. The +instructions @code{lf.itof.s} (single precision) and @code{lf.itof.d} (double +precision) can be used to convert integer values to floating point. +Likewise, instructions @code{lf.ftoi.s} (single precision) and +@code{lf.ftoi.d} (double precision) can be used to convert floating point to +integer. + +OpenRISC also contains privileged special purpose registers (SPRs). The +SPRs are accessed using the @code{l.mfspr} and @code{l.mtspr} instructions. + +@node OpenRISC-Relocs +@subsection Relocations +@cindex OpenRISC relocations +@cindex relocations, OpenRISC + +ELF relocations are available as defined in the OpenRISC architecture +specification. + +@code{R_OR1K_HI_16_IN_INSN} is obtained using @samp{hi} and +@code{R_OR1K_LO_16_IN_INSN} and @code{R_OR1K_SLO16} are obtained using +@samp{lo}. For signed offsets @code{R_OR1K_AHI16} is obtained from +@samp{ha}. For example: + +@example +l.movhi r5, hi(symbol) +l.ori r5, r5, lo(symbol) + +l.movhi r5, ha(symbol) +l.addi r5, r5, lo(symbol) +@end example + +These ``high'' mnemonics extract bits 31:16 of their operand, +and the ``low'' mnemonics extract bits 15:0 of their operand. + +The PC relative relocation @code{R_OR1K_GOTPC_HI16} can be obtained by +enclosing an operand inside of @samp{gotpchi}. Likewise, the +@code{R_OR1K_GOTPC_LO16} relocation can be obtained using @samp{gotpclo}. +These are mostly used when assembling PIC code. For example, the +standard PIC sequence on OpenRISC to get the base of the global offset +table, PC relative, into a register, can be performed as: + +@example +l.jal 0x8 + l.movhi r17, gotpchi(_GLOBAL_OFFSET_TABLE_-4) +l.ori r17, r17, gotpclo(_GLOBAL_OFFSET_TABLE_+0) +l.add r17, r17, r9 +@end example + +Several relocations exist to allow the link editor to perform GOT data +references. The @code{R_OR1K_GOT16} relocation can obtained by enclosing an +operand inside of @samp{got}. For example, assuming the GOT base is in +register @code{r17}. + +@example +l.lwz r19, got(a)(r17) +l.lwz r21, 0(r19) +@end example + +Also, several relocations exist for local GOT references. The +@code{R_OR1K_GOTOFF_AHI16} relocation can obtained by enclosing an operand +inside of @samp{gotoffha}. Likewise, @code{R_OR1K_GOTOFF_LO16} and +@code{R_OR1K_GOTOFF_SLO16} can be obtained by enclosing an operand inside of +@samp{gotofflo}. For example, assuming the GOT base is in register +@code{rl7}: + +@example +l.movhi r19, gotoffha(symbol) +l.add r19, r19, r17 +l.lwz r19, gotofflo(symbol)(r19) +@end example + +The above PC relative relocations use a @code{l.jal} (jump) instruction +and reading of the link register to load the PC. OpenRISC also supports +page offset PC relative locations without a jump instruction using the +@code{l.adrp} instruction. By default the @code{l.adrp} instruction will +create an @code{R_OR1K_PCREL_PG21} relocation. +Likewise, @code{BFD_RELOC_OR1K_LO13} and @code{BFD_RELOC_OR1K_SLO13} can +be obtained by enclosing an operand inside of @samp{po}. For example: + +@example +l.adrp r3, symbol +l.ori r4, r3, po(symbol) +l.lbz r5, po(symbol)(r3) +l.sb po(symbol)(r3), r6 +@end example + +Likewise the page offset relocations can be used with GOT references. The +relocation @code{R_OR1K_GOT_PG21} can be obtained by enclosing an +@code{l.adrp} immediate operand inside of @samp{got}. Likewise, +@code{R_OR1K_GOT_LO13} can be obtained by enclosing an operand inside of +@samp{gotpo}. For example to load the value of a GOT symbol into register +@samp{r5} we can do: + +@example +l.adrp r17, got(_GLOBAL_OFFSET_TABLE_) +l.lwz r5, gotpo(symbol)(r17) +@end example + +There are many relocations that can be requested for access to +thread local storage variables. All of the OpenRISC TLS mnemonics +are supported: + +@itemize @bullet +@item +@code{R_OR1K_TLS_GD_HI16} is requested using @samp{tlsgdhi}. +@item +@code{R_OR1K_TLS_GD_LO16} is requested using @samp{tlsgdlo}. +@item +@code{R_OR1K_TLS_GD_PG21} is requested using @samp{tldgd}. +@item +@code{R_OR1K_TLS_GD_LO13} is requested using @samp{tlsgdpo}. + +@item +@code{R_OR1K_TLS_LDM_HI16} is requested using @samp{tlsldmhi}. +@item +@code{R_OR1K_TLS_LDM_LO16} is requested using @samp{tlsldmlo}. +@item +@code{R_OR1K_TLS_LDM_PG21} is requested using @samp{tldldm}. +@item +@code{R_OR1K_TLS_LDM_LO13} is requested using @samp{tlsldmpo}. + +@item +@code{R_OR1K_TLS_LDO_HI16} is requested using @samp{dtpoffhi}. +@item +@code{R_OR1K_TLS_LDO_LO16} is requested using @samp{dtpofflo}. + +@item +@code{R_OR1K_TLS_IE_HI16} is requested using @samp{gottpoffhi}. +@item +@code{R_OR1K_TLS_IE_AHI16} is requested using @samp{gottpoffha}. +@item +@code{R_OR1K_TLS_IE_LO16} is requested using @samp{gottpofflo}. +@item +@code{R_OR1K_TLS_IE_PG21} is requested using @samp{gottp}. +@item +@code{R_OR1K_TLS_IE_LO13} is requested using @samp{gottppo}. + +@item +@code{R_OR1K_TLS_LE_HI16} is requested using @samp{tpoffhi}. +@item +@code{R_OR1K_TLS_LE_AHI16} is requested using @samp{tpoffha}. +@item +@code{R_OR1K_TLS_LE_LO16} is requested using @samp{tpofflo}. +@item +@code{R_OR1K_TLS_LE_SLO16} also is requested using @samp{tpofflo} +depending on the instruction format. +@end itemize + +Here are some example TLS model sequences. + +First, General Dynamic: + +@example +l.movhi r17, tlsgdhi(symbol) +l.ori r17, r17, tlsgdlo(symbol) +l.add r17, r17, r16 +l.or r3, r17, r17 +l.jal plt(__tls_get_addr) + l.nop +@end example + +Initial Exec: + +@example +l.movhi r17, gottpoffhi(symbol) +l.add r17, r17, r16 +l.lwz r17, gottpofflo(symbol)(r17) +l.add r17, r17, r10 +l.lbs r17, 0(r17) +@end example + +And finally, Local Exec: + +@example +l.movhi r17, tpoffha(symbol) +l.add r17, r17, r10 +l.addi r17, r17, tpofflo(symbol) +l.lbs r17, 0(r17) +@end example + +@node OpenRISC-Float +@section Floating Point + +@cindex floating point, OPENRISC (@sc{ieee}) +@cindex OPENRISC floating point (@sc{ieee}) +OpenRISC uses @sc{ieee} floating-point numbers. + +@node OpenRISC-Directives +@section OpenRISC Machine Directives + +@cindex OPENRISC machine directives +@cindex machine directives, OPENRISC +The OpenRISC version of @code{@value{AS}} supports the following additional +machine directives: + +@table @code +@cindex @code{align} directive, OpenRISC +@item .align +This must be followed by the desired alignment in bytes. + +@cindex @code{word} directive, OpenRISC +@item .word +On the OpenRISC, the @code{.word} directive produces a 32 bit value. + +@cindex @code{nodelay} directive, OpenRISC +@item .nodelay +On the OpenRISC, the @code{.nodelay} directive sets a flag in elf binaries +indicating that the binary is generated catering for no delay slots. + +@cindex @code{proc} directive, OpenRISC +@item .proc +This directive is ignored. Any text following it on the same +line is also ignored. + +@cindex @code{endproc} directive, OpenRISC +@item .endproc +This directive is ignored. Any text following it on the same +line is also ignored. +@end table + +@node OpenRISC-Opcodes +@section Opcodes + +@cindex OpenRISC opcode summary +@cindex opcode summary, OpenRISC +@cindex mnemonics, OpenRISC +@cindex instruction summary, LM32 +For detailed information on the OpenRISC machine instruction set, see +@url{http://www.openrisc.io/architecture/}. + +@code{@value{AS}} implements all the standard OpenRISC opcodes. |