TILEPro Dependent Features
**************************

Options
=======

AS has no machine-dependent command-line options for TILEPro.

Syntax
======

Block comments are delimited by /* and */.  End of line comments may be introduced by #.

Instructions consist of a leading opcode or macro name followed by whitespace and an optional comma-separated list of operands:

     OPCODE [OPERAND, ...]

Instructions must be separated by a newline or semicolon.

There are two ways to write code: either write naked instructions, which the assembler is free to combine into VLIW bundles, or specify the VLIW bundles explicitly.

Bundles are specified using curly braces:

     { ADD r3,r4,r5 ; ADD r7,r8,r9 ; LW r10,r11 }

A bundle can span multiple lines. If you want to put multiple instructions on a line, whether in a bundle or not, you need to separate them with semicolons as in this example.

A bundle may contain one or more instructions, up to the limit specified by the ISA (currently three). If fewer instructions are specified than the hardware supports in a bundle, the assembler inserts fnop instructions automatically.

The assembler will prefer to preserve the ordering of instructions within the bundle, putting the first instruction in a lower-numbered pipeline than the next one, etc.  This fact, combined with the optional use of explicit fnop or nop instructions, allows precise control over which pipeline executes each instruction.

If the instructions cannot be bundled in the listed order, the assembler will automatically try to find a valid pipeline assignment. If there is no way to bundle the instructions together, the assembler reports an error.

The assembler does not yet auto-bundle (automatically combine multiple instructions into one bundle), but it reserves the right to do so in the future.  If you want to force an instruction to run by itself, put it in a bundle explicitly with curly braces and use nop instructions (not fnop) to fill the remaining pipeline slots in that bundle.

Opcode Names
------------

For a complete list of opcodes and descriptions of their semantics, see TILE Processor User Architecture Manual, available upon request at www.tilera.com.

Register Names
--------------

General-purpose registers are represented by predefined symbols of the form rN, where N represents a number between 0 and 63.  However, the following registers have canonical names that must be used instead:

r54
     sp

r55
     lr

r56
     sn

r57
     idn0

r58
     idn1

r59
     udn0

r60
     udn1

r61
     udn2

r62
     udn3

r63
     zero

The assembler will emit a warning if a numeric name is used instead of the canonical name.  The .no_require_canonical_reg_names assembler pseudo-op turns off this warning. .require_canonical_reg_names turns it back on.

Symbolic Operand Modifiers
--------------------------

The assembler supports several modifiers when using symbol addresses in TILEPro instruction operands.  The general syntax is the following:

     modifier(symbol)

The following modifiers are supported:

lo16

     This modifier is used to load the low 16 bits of the symbol's address, sign-extended to a 32-bit value (sign-extension allows it to be range-checked against signed 16 bit immediate operands without complaint).

hi16

     This modifier is used to load the high 16 bits of the symbol's address, also sign-extended to a 32-bit value.

ha16

     ha16(N) is identical to hi16(N), except if lo16(N) is negative it adds one to the hi16(N) value. This way lo16 and ha16 can be added to create any 32-bit value using auli.  For example, here is how you move an arbitrary 32-bit address into r3:

          moveli r3, lo16(sym)
          auli r3, r3, ha16(sym)

got

     This modifier is used to load the offset of the GOT entry corresponding to the symbol.

got_lo16

     This modifier is used to load the sign-extended low 16 bits of the offset of the GOT entry corresponding to the symbol.

got_hi16

     This modifier is used to load the sign-extended high 16 bits of the offset of the GOT entry corresponding to the symbol.

got_ha16

     This modifier is like got_hi16, but it adds one if got_lo16 of the input value is negative.

plt

     This modifier is used for function symbols.  It causes a procedure linkage table, an array of code stubs, to be created at the time the shared object is created or linked against, together with a global offset table entry.  The value is a pc-relative offset to the corresponding stub code in the procedure linkage table.  This arrangement causes the run-time symbol resolver to be called to look up and set the value of the symbol the first time the function is called (at latest; depending environment variables).  It is only safe to leave the symbol unresolved this way if all references are function calls.

tls_gd

     This modifier is used to load the offset of the GOT entry of the symbol's TLS descriptor, to be used for general-dynamic TLS accesses.

tls_gd_lo16

     This modifier is used to load the sign-extended low 16 bits of the offset of the GOT entry of the symbol's TLS descriptor, to be used for general dynamic TLS accesses.

tls_gd_hi16

     This modifier is used to load the sign-extended high 16 bits of the offset of the GOT entry of the symbol's TLS descriptor, to be used for general dynamic TLS accesses.

tls_gd_ha16

     This modifier is like tls_gd_hi16, but it adds one to the value if tls_gd_lo16 of the input value is negative.

tls_ie

     This modifier is used to load the offset of the GOT entry containing the offset of the symbol's address from the TCB, to be used for initial-exec TLS accesses.

tls_ie_lo16

     This modifier is used to load the low 16 bits of the offset of the GOT entry containing the offset of the symbol's address from the TCB, to be used for initial-exec TLS accesses.

tls_ie_hi16

     This modifier is used to load the high 16 bits of the offset of the GOT entry containing the offset of the symbol's address from the TCB, to be used for initial-exec TLS accesses.

tls_ie_ha16

     This modifier is like tls_ie_hi16, but it adds one to the value if tls_ie_lo16 of the input value is negative.

tls_le

     This modifier is used to load the offset of the symbol's address from the TCB, to be used for local-exec TLS accesses.

tls_le_lo16

     This modifier is used to load the low 16 bits of the offset of the symbol's address from the TCB, to be used for local-exec TLS accesses.

tls_le_hi16

     This modifier is used to load the high 16 bits of the offset of the symbol's address from the TCB, to be used for local-exec TLS accesses.

tls_le_ha16

     This modifier is like tls_le_hi16, but it adds one to the value if tls_le_lo16 of the input value is negative.

tls_gd_call

     This modifier is used to tag an instrution as the ``call'' part of a calling sequence for a TLS GD reference of its operand.

tls_gd_add

     This modifier is used to tag an instruction as the ``add'' part of a calling sequence for a TLS GD reference of its operand.

tls_ie_load

     This modifier is used to tag an instruction as the ``load'' part of a calling sequence for a TLS IE reference of its operand.

TILEPro Directives
==================

.align EXPRESSION [, EXPRESSION]
     This is the generic .ALIGN directive.  The first argument is the requested alignment in bytes.

.allow_suspicious_bundles
     Turns on error checking for combinations of instructions in a bundle that probably indicate a programming error.  This is on by default.

.no_allow_suspicious_bundles
     Turns off error checking for combinations of instructions in a bundle that probably indicate a programming error.

.require_canonical_reg_names
     Require that canonical register names be used, and emit a warning if the numeric names are used.  This is on by default.

.no_require_canonical_reg_names
     Permit the use of numeric names for registers that have canonical names.