-.. _code_generator:
-
==========================================
The LLVM Target-Independent Code Generator
==========================================
.partial { background-color: #F88017 }
.yes { background-color: #0F0; }
.yes:before { content: "Y" }
+ .na { background-color: #6666FF; }
+ .na:before { content: "N/A" }
</style>
.. contents::
The two pieces of the LLVM code generator are the high-level interface to the
code generator and the set of reusable components that can be used to build
target-specific backends. The two most important interfaces (:raw-html:`<tt>`
-`TargetMachine`_ :raw-html:`</tt>` and :raw-html:`<tt>` `TargetData`_
+`TargetMachine`_ :raw-html:`</tt>` and :raw-html:`<tt>` `DataLayout`_
:raw-html:`</tt>`) are the only ones that are required to be defined for a
backend to fit into the LLVM system, but the others must be defined if the
reusable code generator components are going to be used.
information (e.g., an ``add`` instruction is almost identical to a ``sub``
instruction). In order to allow the maximum amount of commonality to be
factored out, the LLVM code generator uses the
-`TableGen <TableGenFundamentals.html>`_ tool to describe big chunks of the
+:doc:`TableGen <TableGenFundamentals>` tool to describe big chunks of the
target machine, which allows the use of domain-specific and target-specific
abstractions to reduce the amount of repetition.
properties of the target (such as the instructions and registers it has), and do
not incorporate any particular pieces of code generation algorithms.
-All of the target description classes (except the :raw-html:`<tt>` `TargetData`_
+All of the target description classes (except the :raw-html:`<tt>` `DataLayout`_
:raw-html:`</tt>` class) are designed to be subclassed by the concrete target
implementation, and have virtual methods implemented. To get to these
implementations, the :raw-html:`<tt>` `TargetMachine`_ :raw-html:`</tt>` class
``getFrameInfo``, etc.). This class is designed to be specialized by a concrete
target implementation (e.g., ``X86TargetMachine``) which implements the various
virtual methods. The only required target description class is the
-:raw-html:`<tt>` `TargetData`_ :raw-html:`</tt>` class, but if the code
+:raw-html:`<tt>` `DataLayout`_ :raw-html:`</tt>` class, but if the code
generator components are to be used, the other interfaces should be implemented
as well.
-.. _TargetData:
+.. _DataLayout:
-The ``TargetData`` class
+The ``DataLayout`` class
------------------------
-The ``TargetData`` class is the only required target description class, and it
-is the only class that is not extensible (you cannot derived a new class from
-it). ``TargetData`` specifies information about how the target lays out memory
+The ``DataLayout`` class is the only required target description class, and it
+is the only class that is not extensible (you cannot derive a new class from
+it). ``DataLayout`` specifies information about how the target lays out memory
for structures, the alignment requirements for various data types, the size of
pointers in the target, and whether the target is little-endian or
big-endian.
-.. _targetlowering:
+.. _TargetLowering:
The ``TargetLowering`` class
----------------------------
* the type to use for shift amounts, and
* various high-level characteristics, like whether it is profitable to turn
- division by a constant into a multiplication sequence
+ division by a constant into a multiplication sequence.
+
+.. _TargetRegisterInfo:
The ``TargetRegisterInfo`` class
--------------------------------
The ``TargetRegisterInfo`` class is used to describe the register file of the
target and any interactions between the registers.
-Registers in the code generator are represented in the code generator by
-unsigned integers. Physical registers (those that actually exist in the target
-description) are unique small numbers, and virtual registers are generally
-large. Note that register ``#0`` is reserved as a flag value.
+Registers are represented in the code generator by unsigned integers. Physical
+registers (those that actually exist in the target description) are unique
+small numbers, and virtual registers are generally large. Note that
+register ``#0`` is reserved as a flag value.
Each register in the processor description has an associated
``TargetRegisterDesc`` entry, which provides a textual name for the register
MachineInstr *MI = BuildMI(X86::MOV32ri, 1, DestReg).addImm(42);
// Create the same instr, but insert it at the end of a basic block.
- MachineBasicBlock &MBB = ...
+ MachineBasicBlock &MBB = ...
BuildMI(MBB, X86::MOV32ri, 1, DestReg).addImm(42);
// Create the same instr, but insert it before a specified iterator point.
MI = BuildMI(X86::SAHF, 0);
// Create a self looping branch instruction.
- BuildMI(MBB, X86::JNE, 1).addMBB(&MBB);
+ BuildMI(MBB, X86::JNE, 1).addMBB(&MBB);
The key thing to remember with the ``BuildMI`` functions is that you have to
specify the number of operands that the machine instruction will take. This
SREM or UREM operation. The `legalize types`_ and `legalize operations`_ phases
are responsible for turning an illegal DAG into a legal DAG.
+.. _SelectionDAG-Process:
+
SelectionDAG Instruction Selection Process
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The initial SelectionDAG is na\ :raw-html:`ï`\ vely peephole expanded from
-the LLVM input by the ``SelectionDAGLowering`` class in the
-``lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp`` file. The intent of this pass
+the LLVM input by the ``SelectionDAGBuilder`` class. The intent of this pass
is to expose as much low-level, target-specific details to the SelectionDAG as
possible. This pass is mostly hard-coded (e.g. an LLVM ``add`` turns into an
``SDNode add`` while a ``getelementptr`` is expanded into the obvious
A target implementation tells the legalizer which types are supported (and which
register class to use for them) by calling the ``addRegisterClass`` method in
-its TargetLowering constructor.
+its ``TargetLowering`` constructor.
.. _legalize operations:
.. _Legalizer:
To perform this pattern match, the PowerPC backend includes the following
instruction definitions:
-::
+.. code-block:: text
+ :emphasize-lines: 4-5,9
def FMADDS : AForm_1<59, 29,
(ops F4RC:$FRT, F4RC:$FRA, F4RC:$FRC, F4RC:$FRB),
"fadds $FRT, $FRA, $FRB",
[(set F4RC:$FRT, (fadd F4RC:$FRA, F4RC:$FRB))]>;
-The portion of the instruction definition in bold indicates the pattern used to
-match the instruction. The DAG operators (like ``fmul``/``fadd``) are defined
-in the ``include/llvm/Target/TargetSelectionDAG.td`` file. " ``F4RC``" is the
-register class of the input and result values.
+The highlighted portion of the instruction definitions indicates the pattern
+used to match the instructions. The DAG operators (like ``fmul``/``fadd``)
+are defined in the ``include/llvm/Target/TargetSelectionDAG.td`` file.
+"``F4RC``" is the register class of the input and result values.
The TableGen DAG instruction selector generator reads the instruction patterns
in the ``.td`` file and automatically builds parts of the pattern matching code
specific to the code generator for a particular target. First we start with a
table that summarizes what features are supported by each target.
+.. _target-feature-matrix:
+
Target Feature Matrix
---------------------
:raw-html:`<table border="1" cellspacing="0">`
:raw-html:`<tr>`
:raw-html:`<th>Unknown</th>`
+:raw-html:`<th>Not Applicable</th>`
:raw-html:`<th>No support</th>`
:raw-html:`<th>Partial Support</th>`
:raw-html:`<th>Complete Support</th>`
:raw-html:`</tr>`
:raw-html:`<tr>`
:raw-html:`<td class="unknown"></td>`
+:raw-html:`<td class="na"></td>`
:raw-html:`<td class="no"></td>`
:raw-html:`<td class="partial"></td>`
:raw-html:`<td class="yes"></td>`
:raw-html:`<tr>`
:raw-html:`<th>Feature</th>`
:raw-html:`<th>ARM</th>`
-:raw-html:`<th>CellSPU</th>`
:raw-html:`<th>Hexagon</th>`
:raw-html:`<th>MBlaze</th>`
:raw-html:`<th>MSP430</th>`
:raw-html:`<th>Mips</th>`
-:raw-html:`<th>PTX</th>`
+:raw-html:`<th>NVPTX</th>`
:raw-html:`<th>PowerPC</th>`
:raw-html:`<th>Sparc</th>`
:raw-html:`<th>X86</th>`
:raw-html:`<tr>`
:raw-html:`<td><a href="#feat_reliable">is generally reliable</a></td>`
:raw-html:`<td class="yes"></td> <!-- ARM -->`
-:raw-html:`<td class="no"></td> <!-- CellSPU -->`
:raw-html:`<td class="yes"></td> <!-- Hexagon -->`
:raw-html:`<td class="no"></td> <!-- MBlaze -->`
:raw-html:`<td class="unknown"></td> <!-- MSP430 -->`
:raw-html:`<td class="yes"></td> <!-- Mips -->`
-:raw-html:`<td class="no"></td> <!-- PTX -->`
+:raw-html:`<td class="yes"></td> <!-- NVPTX -->`
:raw-html:`<td class="yes"></td> <!-- PowerPC -->`
:raw-html:`<td class="yes"></td> <!-- Sparc -->`
:raw-html:`<td class="yes"></td> <!-- X86 -->`
:raw-html:`<tr>`
:raw-html:`<td><a href="#feat_asmparser">assembly parser</a></td>`
:raw-html:`<td class="no"></td> <!-- ARM -->`
-:raw-html:`<td class="no"></td> <!-- CellSPU -->`
:raw-html:`<td class="no"></td> <!-- Hexagon -->`
:raw-html:`<td class="yes"></td> <!-- MBlaze -->`
:raw-html:`<td class="no"></td> <!-- MSP430 -->`
:raw-html:`<td class="no"></td> <!-- Mips -->`
-:raw-html:`<td class="no"></td> <!-- PTX -->`
+:raw-html:`<td class="no"></td> <!-- NVPTX -->`
:raw-html:`<td class="no"></td> <!-- PowerPC -->`
:raw-html:`<td class="no"></td> <!-- Sparc -->`
:raw-html:`<td class="yes"></td> <!-- X86 -->`
:raw-html:`<tr>`
:raw-html:`<td><a href="#feat_disassembler">disassembler</a></td>`
:raw-html:`<td class="yes"></td> <!-- ARM -->`
-:raw-html:`<td class="no"></td> <!-- CellSPU -->`
:raw-html:`<td class="no"></td> <!-- Hexagon -->`
:raw-html:`<td class="yes"></td> <!-- MBlaze -->`
:raw-html:`<td class="no"></td> <!-- MSP430 -->`
:raw-html:`<td class="no"></td> <!-- Mips -->`
-:raw-html:`<td class="no"></td> <!-- PTX -->`
+:raw-html:`<td class="na"></td> <!-- NVPTX -->`
:raw-html:`<td class="no"></td> <!-- PowerPC -->`
:raw-html:`<td class="no"></td> <!-- Sparc -->`
:raw-html:`<td class="yes"></td> <!-- X86 -->`
:raw-html:`<tr>`
:raw-html:`<td><a href="#feat_inlineasm">inline asm</a></td>`
:raw-html:`<td class="yes"></td> <!-- ARM -->`
-:raw-html:`<td class="no"></td> <!-- CellSPU -->`
:raw-html:`<td class="yes"></td> <!-- Hexagon -->`
:raw-html:`<td class="yes"></td> <!-- MBlaze -->`
:raw-html:`<td class="unknown"></td> <!-- MSP430 -->`
:raw-html:`<td class="no"></td> <!-- Mips -->`
-:raw-html:`<td class="unknown"></td> <!-- PTX -->`
+:raw-html:`<td class="yes"></td> <!-- NVPTX -->`
:raw-html:`<td class="yes"></td> <!-- PowerPC -->`
:raw-html:`<td class="unknown"></td> <!-- Sparc -->`
:raw-html:`<td class="yes"></td> <!-- X86 -->`
:raw-html:`<tr>`
:raw-html:`<td><a href="#feat_jit">jit</a></td>`
:raw-html:`<td class="partial"><a href="#feat_jit_arm">*</a></td> <!-- ARM -->`
-:raw-html:`<td class="no"></td> <!-- CellSPU -->`
:raw-html:`<td class="no"></td> <!-- Hexagon -->`
:raw-html:`<td class="no"></td> <!-- MBlaze -->`
:raw-html:`<td class="unknown"></td> <!-- MSP430 -->`
:raw-html:`<td class="yes"></td> <!-- Mips -->`
-:raw-html:`<td class="unknown"></td> <!-- PTX -->`
+:raw-html:`<td class="na"></td> <!-- NVPTX -->`
:raw-html:`<td class="yes"></td> <!-- PowerPC -->`
:raw-html:`<td class="unknown"></td> <!-- Sparc -->`
:raw-html:`<td class="yes"></td> <!-- X86 -->`
:raw-html:`<tr>`
:raw-html:`<td><a href="#feat_objectwrite">.o file writing</a></td>`
:raw-html:`<td class="no"></td> <!-- ARM -->`
-:raw-html:`<td class="no"></td> <!-- CellSPU -->`
:raw-html:`<td class="no"></td> <!-- Hexagon -->`
:raw-html:`<td class="yes"></td> <!-- MBlaze -->`
:raw-html:`<td class="no"></td> <!-- MSP430 -->`
:raw-html:`<td class="no"></td> <!-- Mips -->`
-:raw-html:`<td class="no"></td> <!-- PTX -->`
+:raw-html:`<td class="na"></td> <!-- NVPTX -->`
:raw-html:`<td class="no"></td> <!-- PowerPC -->`
:raw-html:`<td class="no"></td> <!-- Sparc -->`
:raw-html:`<td class="yes"></td> <!-- X86 -->`
:raw-html:`<tr>`
:raw-html:`<td><a hr:raw-html:`ef="#feat_tailcall">tail calls</a></td>`
:raw-html:`<td class="yes"></td> <!-- ARM -->`
-:raw-html:`<td class="no"></td> <!-- CellSPU -->`
:raw-html:`<td class="yes"></td> <!-- Hexagon -->`
:raw-html:`<td class="no"></td> <!-- MBlaze -->`
:raw-html:`<td class="unknown"></td> <!-- MSP430 -->`
:raw-html:`<td class="no"></td> <!-- Mips -->`
-:raw-html:`<td class="unknown"></td> <!-- PTX -->`
+:raw-html:`<td class="no"></td> <!-- NVPTX -->`
:raw-html:`<td class="yes"></td> <!-- PowerPC -->`
:raw-html:`<td class="unknown"></td> <!-- Sparc -->`
:raw-html:`<td class="yes"></td> <!-- X86 -->`
:raw-html:`<tr>`
:raw-html:`<td><a href="#feat_segstacks">segmented stacks</a></td>`
:raw-html:`<td class="no"></td> <!-- ARM -->`
-:raw-html:`<td class="no"></td> <!-- CellSPU -->`
:raw-html:`<td class="no"></td> <!-- Hexagon -->`
:raw-html:`<td class="no"></td> <!-- MBlaze -->`
:raw-html:`<td class="no"></td> <!-- MSP430 -->`
:raw-html:`<td class="no"></td> <!-- Mips -->`
-:raw-html:`<td class="no"></td> <!-- PTX -->`
+:raw-html:`<td class="no"></td> <!-- NVPTX -->`
:raw-html:`<td class="no"></td> <!-- PowerPC -->`
:raw-html:`<td class="no"></td> <!-- Sparc -->`
:raw-html:`<td class="partial"><a href="#feat_segstacks_x86">*</a></td> <!-- X86 -->`
Tail call optimization, callee reusing the stack of the caller, is currently
supported on x86/x86-64 and PowerPC. It is performed if:
-* Caller and callee have the calling convention ``fastcc`` or ``cc 10`` (GHC
- call convention).
+* Caller and callee have the calling convention ``fastcc``, ``cc 10`` (GHC
+ calling convention) or ``cc 11`` (HiPE calling convention).
* The call is a tail call - in tail position (ret immediately follows call and
ret uses value of call or is void).
TODO - More to come.
-The PTX backend
----------------
+The NVPTX backend
+-----------------
-The PTX code generator lives in the lib/Target/PTX directory. It is currently a
-work-in-progress, but already supports most of the code generation functionality
-needed to generate correct PTX kernels for CUDA devices.
+The NVPTX code generator under lib/Target/NVPTX is an open-source version of
+the NVIDIA NVPTX code generator for LLVM. It is contributed by NVIDIA and is
+a port of the code generator used in the CUDA compiler (nvcc). It targets the
+PTX 3.0/3.1 ISA and can target any compute capability greater than or equal to
+2.0 (Fermi).
-The code generator can target PTX 2.0+, and shader model 1.0+. The PTX ISA
-Reference Manual is used as the primary source of ISA information, though an
-effort is made to make the output of the code generator match the output of the
-NVidia nvcc compiler, whenever possible.
+This target is of production quality and should be completely compatible with
+the official NVIDIA toolchain.
Code Generator Options:
:raw-html:`<th>Description</th>`
:raw-html:`</tr>`
:raw-html:`<tr>`
-:raw-html:`<td>``double``</td>`
-:raw-html:`<td align="left">If enabled, the map_f64_to_f32 directive is disabled in the PTX output, allowing native double-precision arithmetic</td>`
+:raw-html:`<td>sm_20</td>`
+:raw-html:`<td align="left">Set shader model/compute capability to 2.0</td>`
+:raw-html:`</tr>`
+:raw-html:`<tr>`
+:raw-html:`<td>sm_21</td>`
+:raw-html:`<td align="left">Set shader model/compute capability to 2.1</td>`
+:raw-html:`</tr>`
+:raw-html:`<tr>`
+:raw-html:`<td>sm_30</td>`
+:raw-html:`<td align="left">Set shader model/compute capability to 3.0</td>`
+:raw-html:`</tr>`
+:raw-html:`<tr>`
+:raw-html:`<td>sm_35</td>`
+:raw-html:`<td align="left">Set shader model/compute capability to 3.5</td>`
:raw-html:`</tr>`
:raw-html:`<tr>`
-:raw-html:`<td>``no-fma``</td>`
-:raw-html:`<td align="left">Disable generation of Fused-Multiply Add instructions, which may be beneficial for some devices</td>`
+:raw-html:`<td>ptx30</td>`
+:raw-html:`<td align="left">Target PTX 3.0</td>`
:raw-html:`</tr>`
:raw-html:`<tr>`
-:raw-html:`<td>``smxy / computexy``</td>`
-:raw-html:`<td align="left">Set shader model/compute capability to x.y, e.g. sm20 or compute13</td>`
+:raw-html:`<td>ptx31</td>`
+:raw-html:`<td align="left">Target PTX 3.1</td>`
:raw-html:`</tr>`
:raw-html:`</table>`
-Working:
-
-* Arithmetic instruction selection (including combo FMA)
-
-* Bitwise instruction selection
-
-* Control-flow instruction selection
-
-* Function calls (only on SM 2.0+ and no return arguments)
-
-* Addresses spaces (0 = global, 1 = constant, 2 = local, 4 = shared)
-
-* Thread synchronization (bar.sync)
-
-* Special register reads ([N]TID, [N]CTAID, PMx, CLOCK, etc.)
-
-In Progress:
-
-* Robust call instruction selection
-
-* Stack frame allocation
-
-* Device-specific instruction scheduling optimizations
projects / oota-llvm.git / blobdiff