593 lines
18 KiB
Plaintext
593 lines
18 KiB
Plaintext
@c Copyright (C) 2000-2016 Free Software Foundation, Inc.
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@c This is part of the GAS manual.
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@c For copying conditions, see the file as.texinfo.
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@ifset GENERIC
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@page
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@node ARC-Dependent
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@chapter ARC Dependent Features
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@end ifset
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@ifclear GENERIC
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@node Machine Dependencies
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@chapter ARC Dependent Features
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@end ifclear
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@set ARC_CORE_DEFAULT 6
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@cindex ARC support
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@menu
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* ARC Options:: Options
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* ARC Syntax:: Syntax
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* ARC Directives:: ARC Machine Directives
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* ARC Modifiers:: ARC Assembler Modifiers
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* ARC Symbols:: ARC Pre-defined Symbols
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* ARC Opcodes:: Opcodes
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@end menu
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@node ARC Options
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@section Options
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@cindex ARC options
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@cindex options for ARC
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The following options control the type of CPU for which code is
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assembled, and generic constraints on the code generated:
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@table @code
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@item -mcpu=@var{cpu}
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@cindex @code{-mcpu=@var{cpu}} command line option, ARC
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Set architecture type and register usage for @var{cpu}. There are
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also shortcut alias options available for backward compatibility and
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convenience. Supported values for @var{cpu} are
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@table @code
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@cindex @code{mA6} command line option, ARC
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@cindex @code{marc600} command line option, ARC
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@item arc600
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Assemble for ARC 600. Aliases: @code{-mA6}, @code{-mARC600}.
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@item arc601
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@cindex @code{mARC601} command line option, ARC
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Assemble for ARC 601. Alias: @code{-mARC601}.
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@item arc700
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@cindex @code{mA7} command line option, ARC
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@cindex @code{mARC700} command line option, ARC
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Assemble for ARC 700. Aliases: @code{-mA7}, @code{-mARC700}.
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@item arcem
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@cindex @code{mEM} command line option, ARC
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Assemble for ARC EM. Aliases: @code{-mEM}
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@item archs
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@cindex @code{mHS} command line option, ARC
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Assemble for ARC HS. Aliases: @code{-mHS}, @code{-mav2hs}.
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@end table
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Note: the @code{.cpu} directive can to be used to select a core
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variant from within assembly code.
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@cindex @code{-EB} command line option, ARC
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@item -EB
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This option specifies that the output generated by the assembler should
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be marked as being encoded for a big-endian processor.
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@cindex @code{-EL} command line option, ARC
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@item -EL
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This option specifies that the output generated by the assembler should
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be marked as being encoded for a little-endian processor - this is the
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default.
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@cindex @code{-mcode-density} command line option, ARC
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@item -mcode-density
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This option turns on Code Density instructions. Only valid for ARC EM
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processors.
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@cindex @code{-mrelax} command line option, ARC
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@item -mrelax
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Enable support for assembly-time relaxation. The assembler will
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replace a longer version of an instruction with a shorter one,
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whenever it is possible.
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@end table
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@node ARC Syntax
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@section Syntax
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@menu
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* ARC-Chars:: Special Characters
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* ARC-Regs:: Register Names
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@end menu
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@node ARC-Chars
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@subsection Special Characters
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@table @code
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@item %
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@cindex register name prefix character, ARC
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@cindex ARC register name prefix character
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A register name can optionally be prefixed by a @samp{%} character. So
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register @code{%r0} is equivalent to @code{r0} in the assembly code.
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@item #
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@cindex line comment character, ARC
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@cindex ARC line comment character
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The presence of a @samp{#} character within a line (but not at the
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start of a line) indicates the start of a comment that extends to the
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end of the current line.
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@emph{Note:} if a line starts with a @samp{#} character then it can
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also be a logical line number directive (@pxref{Comments}) or a
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preprocessor control command (@pxref{Preprocessing}).
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@item @@
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@cindex symbol prefix character, ARC
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@cindex ARC symbol prefix character
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Prefixing an operand with an @samp{@@} specifies that the operand is a
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symbol and not a register. This is how the assembler disambiguates
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the use of an ARC register name as a symbol. So the instruction
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@example
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mov r0, @@r0
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@end example
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moves the address of symbol @code{r0} into register @code{r0}.
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@item `
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@cindex line separator, ARC
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@cindex statement separator, ARC
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@cindex ARC line separator
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The @samp{`} (backtick) character is used to separate statements on a
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single line.
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@cindex line
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@item -
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@cindex C preprocessor macro separator, ARC
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@cindex ARC C preprocessor macro separator
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Used as a separator to obtain a sequence of commands from a C
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preprocessor macro.
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@end table
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@node ARC-Regs
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@subsection Register Names
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@cindex ARC register names
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@cindex register names, ARC
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The ARC assembler uses the following register names for its core
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registers:
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@table @code
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@item r0-r31
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@cindex core general registers, ARC
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@cindex ARC core general registers
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The core general registers. Registers @code{r26} through @code{r31}
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have special functions, and are usually referred to by those synonyms.
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@item gp
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@cindex global pointer, ARC
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@cindex ARC global pointer
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The global pointer and a synonym for @code{r26}.
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@item fp
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@cindex frame pointer, ARC
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@cindex ARC frame pointer
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The frame pointer and a synonym for @code{r27}.
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@item sp
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@cindex stack pointer, ARC
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@cindex ARC stack pointer
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The stack pointer and a synonym for @code{r28}.
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@item ilink1
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@cindex level 1 interrupt link register, ARC
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@cindex ARC level 1 interrupt link register
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For ARC 600 and ARC 700, the level 1 interrupt link register and a
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synonym for @code{r29}. Not supported for ARCv2.
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@item ilink
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@cindex interrupt link register, ARC
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@cindex ARC interrupt link register
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For ARCv2, the interrupt link register and a synonym for @code{r29}.
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Not supported for ARC 600 and ARC 700.
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@item ilink2
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@cindex level 2 interrupt link register, ARC
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@cindex ARC level 2 interrupt link register
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For ARC 600 and ARC 700, the level 2 interrupt link register and a
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synonym for @code{r30}. Not supported for ARC v2.
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@item blink
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@cindex link register, ARC
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@cindex ARC link register
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The link register and a synonym for @code{r31}.
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@item r32-r59
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@cindex extension core registers, ARC
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@cindex ARC extension core registers
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The extension core registers.
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@item lp_count
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@cindex loop counter, ARC
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@cindex ARC loop counter
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The loop count register.
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@item pcl
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@cindex word aligned program counter, ARC
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@cindex ARC word aligned program counter
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The word aligned program counter.
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@end table
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In addition the ARC processor has a large number of @emph{auxiliary
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registers}. The precise set depends on the extensions being
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supported, but the following baseline set are always defined:
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@table @code
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@item identity
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@cindex Processor Identification register, ARC
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@cindex ARC Processor Identification register
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Processor Identification register. Auxiliary register address 0x4.
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@item pc
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@cindex Program Counter, ARC
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@cindex ARC Program Counter
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Program Counter. Auxiliary register address 0x6.
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@item status32
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@cindex Status register, ARC
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@cindex ARC Status register
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Status register. Auxiliary register address 0x0a.
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@item bta
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@cindex Branch Target Address, ARC
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@cindex ARC Branch Target Address
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Branch Target Address. Auxiliary register address 0x412.
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@item ecr
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@cindex Exception Cause Register, ARC
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@cindex ARC Exception Cause Register
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Exception Cause Register. Auxiliary register address 0x403.
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@item int_vector_base
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@cindex Interrupt Vector Base address, ARC
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@cindex ARC Interrupt Vector Base address
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Interrupt Vector Base address. Auxiliary register address 0x25.
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@item status32_p0
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@cindex Stored STATUS32 register on entry to level P0 interrupts, ARC
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@cindex ARC Stored STATUS32 register on entry to level P0 interrupts
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Stored STATUS32 register on entry to level P0 interrupts. Auxiliary
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register address 0xb.
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@item aux_user_sp
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@cindex Saved User Stack Pointer, ARC
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@cindex ARC Saved User Stack Pointer
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Saved User Stack Pointer. Auxiliary register address 0xd.
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@item eret
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@cindex Exception Return Address, ARC
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@cindex ARC Exception Return Address
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Exception Return Address. Auxiliary register address 0x400.
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@item erbta
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@cindex BTA saved on exception entry, ARC
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@cindex ARC BTA saved on exception entry
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BTA saved on exception entry. Auxiliary register address 0x401.
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@item erstatus
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@cindex STATUS32 saved on exception, ARC
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@cindex ARC STATUS32 saved on exception
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STATUS32 saved on exception. Auxiliary register address 0x402.
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@item bcr_ver
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@cindex Build Configuration Registers Version, ARC
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@cindex ARC Build Configuration Registers Version
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Build Configuration Registers Version. Auxiliary register address 0x60.
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@item bta_link_build
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@cindex Build configuration for: BTA Registers, ARC
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@cindex ARC Build configuration for: BTA Registers
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Build configuration for: BTA Registers. Auxiliary register address 0x63.
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@item vecbase_ac_build
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@cindex Build configuration for: Interrupts, ARC
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@cindex ARC Build configuration for: Interrupts
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Build configuration for: Interrupts. Auxiliary register address 0x68.
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@item rf_build
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@cindex Build configuration for: Core Registers, ARC
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@cindex ARC Build configuration for: Core Registers
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Build configuration for: Core Registers. Auxiliary register address 0x6e.
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@item dccm_build
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@cindex DCCM RAM Configuration Register, ARC
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@cindex ARC DCCM RAM Configuration Register
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DCCM RAM Configuration Register. Auxiliary register address 0xc1.
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@end table
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Additional auxiliary register names are defined according to the
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processor architecture version and extensions selected by the options.
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@node ARC Directives
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@section ARC Machine Directives
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@cindex machine directives, ARC
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@cindex ARC machine directives
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The ARC version of @code{@value{AS}} supports the following additional
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machine directives:
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@table @code
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@cindex @code{lcomm} directive
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@item .lcomm @var{symbol}, @var{length}[, @var{alignment}]
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Reserve @var{length} (an absolute expression) bytes for a local common
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denoted by @var{symbol}. The section and value of @var{symbol} are
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those of the new local common. The addresses are allocated in the bss
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section, so that at run-time the bytes start off zeroed. Since
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@var{symbol} is not declared global, it is normally not visible to
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@code{@value{LD}}. The optional third parameter, @var{alignment},
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specifies the desired alignment of the symbol in the bss section,
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specified as a byte boundary (for example, an alignment of 16 means
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that the least significant 4 bits of the address should be zero). The
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alignment must be an absolute expression, and it must be a power of
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two. If no alignment is specified, as will set the alignment to the
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largest power of two less than or equal to the size of the symbol, up
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to a maximum of 16.
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@cindex @code{lcommon} directive, ARC
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@item .lcommon @var{symbol}, @var{length}[, @var{alignment}]
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The same as @code{lcomm} directive.
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@cindex @code{cpu} directive, ARC
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@item .cpu @var{cpu}
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The @code{.cpu} directive must be followed by the desired core
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version. Permitted values for CPU are:
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@table @code
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@item ARC600
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Assemble for the ARC600 instruction set.
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@item ARC700
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Assemble for the ARC700 instruction set.
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@item EM
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Assemble for the ARC EM instruction set.
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@item HS
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Assemble for the ARC HS instruction set.
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@end table
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Note: the @code{.cpu} directive overrides the command line option
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@code{-mcpu=@var{cpu}}; a warning is emitted when the version is not
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consistent between the two.
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@item .extAuxRegister @var{name}, @var{addr}, @var{mode}
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@cindex @code{extAuxRegister} directive, ARC
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Auxiliary registers can be defined in the assembler source code by
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using this directive. The first parameter, @var{name}, is the name of the
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new auxiliary register. The second parameter, @var{addr}, is
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address the of the auxiliary register. The third parameter,
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@var{mode}, specifies whether the register is readable and/or writable
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and is one of:
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@table @code
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@item r
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Read only;
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@item w
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Write only;
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@item r|w
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Read and write.
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@end table
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For example:
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@example
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.extAuxRegister mulhi, 0x12, w
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@end example
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specifies a write only extension auxiliary register, @var{mulhi} at
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address 0x12.
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@item .extCondCode @var{suffix}, @var{val}
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@cindex @code{extCondCode} directive, ARC
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ARC supports extensible condition codes. This directive defines a new
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condition code, to be known by the suffix, @var{suffix} and will
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depend on the value, @var{val} in the condition code.
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For example:
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@example
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.extCondCode is_busy,0x14
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add.is_busy r1,r2,r3
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@end example
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will only execute the @code{add} instruction if the condition code
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value is 0x14.
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@item .extCoreRegister @var{name}, @var{regnum}, @var{mode}, @var{shortcut}
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@cindex @code{extCoreRegister} directive, ARC
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Specifies an extension core register named @var{name} as a synonym for
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the register numbered @var{regnum}. The register number must be
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between 32 and 59. The third argument, @var{mode}, indicates whether
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the register is readable and/or writable and is one of:
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@table @code
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@item r
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Read only;
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@item w
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Write only;
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@item r|w
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Read and write.
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@end table
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The final parameter, @var{shortcut} indicates whether the register has
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a short cut in the pipeline. The valid values are:
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@table @code
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@item can_shortcut
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The register has a short cut in the pipeline;
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@item cannot_shortcut
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The register does not have a short cut in the pipeline.
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@end table
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For example:
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@example
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.extCoreRegister mlo, 57, r , can_shortcut
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@end example
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defines a read only extension core register, @code{mlo}, which is
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register 57, and can short cut the pipeline.
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@item .extInstruction @var{name}, @var{opcode}, @var{subopcode}, @var{suffixclass}, @var{syntaxclass}
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@cindex @code{extInstruction} directive, ARC
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ARC allows the user to specify extension instructions. These
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extension instructions are not macros; the assembler creates encodings
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for use of these instructions according to the specification by the
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user.
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The first argument, @var{name}, gives the name of the instruction.
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The second argument, @var{opcode}, is the opcode to be used (bits 31:27
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in the encoding).
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The third argument, @var{subopcode}, is the sub-opcode to be used, but
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the correct value also depends on the fifth argument,
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@var{syntaxclass}
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The fourth argument, @var{suffixclass}, determines the kinds of
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suffixes to be allowed. Valid values are:
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@table @code
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@item SUFFIX_NONE
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No suffixes are permitted;
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@item SUFFIX_COND
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Conditional suffixes are permitted;
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@item SUFFIX_FLAG
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Flag setting suffixes are permitted.
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@item SUFFIX_COND|SUFFIX_FLAG
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Both conditional and flag setting suffices are permitted.
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@end table
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The fifth and final argument, @var{syntaxclass}, determines the syntax
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class for the instruction. It can have the following values:
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@table @code
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@item SYNTAX_2OP
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Two Operand Instruction;
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@item SYNTAX_3OP
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Three Operand Instruction.
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@end table
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The syntax class may be followed by @samp{|} and one of the following
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modifiers.
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@table @code
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@item OP1_MUST_BE_IMM
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Modifies syntax class @code{SYNTAX_3OP}, specifying that the first
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operand of a three-operand instruction must be an immediate (i.e., the
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result is discarded). This is usually used to set the flags using
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specific instructions and not retain results.
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@item OP1_IMM_IMPLIED
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Modifies syntax class @code{SYNTAX_20P}, specifying that there is an
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implied immediate destination operand which does not appear in the
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syntax.
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For example, if the source code contains an instruction like:
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@example
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inst r1,r2
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@end example
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the first argument is an implied immediate (that is, the result is
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discarded). This is the same as though the source code were: inst
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0,r1,r2.
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@end table
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For example, defining a 64-bit multiplier with immediate operands:
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@example
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.extInstruction mp64, 0x07, 0x2d, SUFFIX_COND|SUFFIX_FLAG,
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SYNTAX_3OP|OP1_MUST_BE_IMM
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@end example
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which specifies an extension instruction named @code{mp64} with 3
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operands. It sets the flags and can be used with a condition code,
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for which the first operand is an immediate, i.e. equivalent to
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discarding the result of the operation.
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A two operands instruction variant would be:
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@example
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.extInstruction mul64, 0x07, 0x2d, SUFFIX_COND,
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SYNTAX_2OP|OP1_IMM_IMPLIED
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@end example
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which describes a two operand instruction with an implicit first
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immediate operand. The result of this operation would be discarded.
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@end table
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@node ARC Modifiers
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@section ARC Assembler Modifiers
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The following additional assembler modifiers have been added for
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position-independent code. These modifiers are available only with
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the ARC 700 and above processors and generate relocation entries,
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which are interpreted by the linker as follows:
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@table @code
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@item @@pcl(@var{symbol})
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@cindex @@pcl(@var{symbol}), ARC modifier
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Relative distance of @var{symbol}'s from the current program counter
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location.
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@item @@gotpc(@var{symbol})
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@cindex @@gotpc(@var{symbol}), ARC modifier
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Relative distance of @var{symbol}'s Global Offset Table entry from the
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current program counter location.
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@item @@gotoff(@var{symbol})
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@cindex @@gotoff(@var{symbol}), ARC modifier
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Distance of @var{symbol} from the base of the Global Offset Table.
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@item @@plt(@var{symbol})
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@cindex @@plt(@var{symbol}), ARC modifier
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Distance of @var{symbol}'s Procedure Linkage Table entry from the
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current program counter. This is valid only with branch and link
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instructions and PC-relative calls.
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@item @@sda(@var{symbol})
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@cindex @@sda(@var{symbol}), ARC modifier
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Relative distance of @var{symbol} from the base of the Small Data
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|
Pointer.
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@end table
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@node ARC Symbols
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@section ARC Pre-defined Symbols
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The following assembler symbols will prove useful when developing
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|
position-independent code. These symbols are available only with the
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|
ARC 700 and above processors.
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|
@table @code
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@item __GLOBAL_OFFSET_TABLE__
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@cindex __GLOBAL_OFFSET_TABLE__, ARC pre-defined symbol
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|
Symbol referring to the base of the Global Offset Table.
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@item __DYNAMIC__
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@cindex __DYNAMIC__, ARC pre-defined symbol
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An alias for the Global Offset Table
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|
@code{Base__GLOBAL_OFFSET_TABLE__}. It can be used only with
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@code{@@gotpc} modifiers.
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@end table
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@node ARC Opcodes
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@section Opcodes
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@cindex ARC opcodes
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|
@cindex opcodes for ARC
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For information on the ARC instruction set, see @cite{ARC Programmers
|
|
Reference Manual}, available where you download the processor IP library.
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