Subversion Repositories openrisc

@c Copyright 2005

@c 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 BFIN-Dependent

@chapter Blackfin Dependent Features

@end ifset

@ifclear GENERIC

@node Machine Dependencies

@chapter Blackfin Dependent Features

@end ifclear

@cindex Blackfin support

@menu

* BFIN Syntax::                 BFIN Syntax

* BFIN Directives::             BFIN Directives

@end menu

@node BFIN Syntax

@section Syntax

@cindex BFIN syntax

@cindex syntax, BFIN

@table @code

@item Special Characters

Assembler input is free format and may appear anywhere on the line.

One instruction may extend across multiple lines or more than one

instruction may appear on the same line.  White space (space, tab,

comments or newline) may appear anywhere between tokens.  A token must

not have embedded spaces.  Tokens include numbers, register names,

keywords, user identifiers, and also some multicharacter special

symbols like "+=", "/*" or "||".

@item Instruction Delimiting

A semicolon must terminate every instruction.  Sometimes a complete

instruction will consist of more than one operation.  There are two

cases where this occurs.  The first is when two general operations

are combined.  Normally a comma separates the different parts, as in

@smallexample

a0= r3.h * r2.l, a1 = r3.l * r2.h ;

@end smallexample

The second case occurs when a general instruction is combined with one

or two memory references for joint issue.  The latter portions are

set off by a "||" token.

@smallexample

a0 = r3.h * r2.l || r1 = [p3++] || r4 = [i2++];

@end smallexample

@item Register Names

The assembler treats register names and instruction keywords in a case

insensitive manner.  User identifiers are case sensitive.  Thus, R3.l,

R3.L, r3.l and r3.L are all equivalent input to the assembler.

Register names are reserved and may not be used as program identifiers.

Some operations (such as "Move Register") require a register pair.

Register pairs are always data registers and are denoted using a colon,

eg., R3:2.  The larger number must be written firsts.  Note that the

hardware only supports odd-even pairs, eg., R7:6, R5:4, R3:2, and R1:0.

Some instructions (such as --SP (Push Multiple)) require a group of

adjacent registers.  Adjacent registers are denoted in the syntax by

the range enclosed in parentheses and separated by a colon, eg., (R7:3).

Again, the larger number appears first.

Portions of a particular register may be individually specified.  This

is written with a dot (".") following the register name and then a

letter denoting the desired portion.  For 32-bit registers, ".H"

denotes the most significant ("High") portion.  ".L" denotes the

least-significant portion.  The subdivisions of the 40-bit registers

are described later.

@item Accumulators

The set of 40-bit registers A1 and A0 that normally contain data that

is being manipulated.  Each accumulator can be accessed in four ways.

@table @code

@item one 40-bit register

The register will be referred to as A1 or A0.

@item one 32-bit register

The registers are designated as A1.W or A0.W.

@item two 16-bit registers

The registers are designated as A1.H, A1.L, A0.H or A0.L.

@item one 8-bit register

The registers are designated as A1.X or A0.X for the bits that

extend beyond bit 31.

@end table

@item Data Registers

The set of 32-bit registers (R0, R1, R2, R3, R4, R5, R6 and R7) that

normally contain data for manipulation.  These are abbreviated as

D-register or Dreg.  Data registers can be accessed as 32-bit registers

or as two independent 16-bit registers.  The least significant 16 bits

of each register is called the "low" half and is designated with ".L"

following the register name.  The most significant 16 bits are called

the "high" half and is designated with ".H" following the name.

@smallexample

   R7.L, r2.h, r4.L, R0.H

@end smallexample

@item Pointer Registers

The set of 32-bit registers (P0, P1, P2, P3, P4, P5, SP and FP) that

normally contain byte addresses of data structures.  These are

abbreviated as P-register or Preg.

@smallexample

p2, p5, fp, sp

@end smallexample

@item Stack Pointer SP

The stack pointer contains the 32-bit address of the last occupied

byte location in the stack.  The stack grows by decrementing the

stack pointer.

@item Frame Pointer FP

The frame pointer contains the 32-bit address of the previous frame

pointer in the stack.  It is located at the top of a frame.

@item Loop Top

LT0 and LT1.  These registers contain the 32-bit address of the top of

a zero overhead loop.

@item Loop Count

LC0 and LC1.  These registers contain the 32-bit counter of the zero

overhead loop executions.

@item Loop Bottom

LB0 and LB1.  These registers contain the 32-bit address of the bottom

of a zero overhead loop.

@item Index Registers

The set of 32-bit registers (I0, I1, I2, I3) that normally contain byte

addresses of data structures.  Abbreviated I-register or Ireg.

@item Modify Registers

The set of 32-bit registers (M0, M1, M2, M3) that normally contain

offset values that are added and subracted to one of the index

registers.  Abbreviated as Mreg.

@item Length Registers

The set of 32-bit registers (L0, L1, L2, L3) that normally contain the

length in bytes of the circular buffer.  Abbreviated as Lreg.  Clear

the Lreg to disable circular addressing for the corresponding Ireg.

@item Base Registers

The set of 32-bit registers (B0, B1, B2, B3) that normally contain the

base address in bytes of the circular buffer.  Abbreviated as Breg.

@item Floating Point

The Blackfin family has no hardware floating point but the .float

directive generates ieee floating point numbers for use with software

floating point libraries.

@item Blackfin Opcodes

For detailed information on the Blackfin machine instruction set, see

the Blackfin(r) Processor Instruction Set Reference.

@end table

@node BFIN Directives

@section Directives

@cindex BFIN directives

@cindex directives, BFIN

The following directives are provided for compatibility with the VDSP assembler.

@table @code

@item .byte2

Initializes a four byte data object.

@item .byte4

Initializes a two byte data object.

@item .db

TBD

@item .dd

TBD

@item .dw

TBD

@item .var

Define and initialize a 32 bit data object.

@end table