familiar with the `target description`_ and `machine code representation`_
classes. If you want to add a backend for a new target, you will need to
`implement the target description`_ classes for your new target and understand
-the `LLVM code representation <LangRef.html>`_. If you are interested in
+the :doc:`LLVM code representation <LangRef>`. If you are interested in
implementing a new `code generation algorithm`_, it should only depend on the
target-description and machine code representation classes, ensuring that it is
portable.
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
-:doc:`TableGen <TableGenFundamentals>` tool to describe big chunks of the
+:doc:`TableGen/index` 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.
virtual registers with a physical register in the set.
The target-specific implementations of these classes is auto-generated from a
-`TableGen <TableGenFundamentals.html>`_ description of the register file.
+:doc:`TableGen/index` description of the register file.
.. _TargetInstrInfo:
-----------------------------
The ``TargetInstrInfo`` class is used to describe the machine instructions
-supported by the target. It is essentially an array of ``TargetInstrDescriptor``
-objects, each of which describes one instruction the target
-supports. Descriptors define things like the mnemonic for the opcode, the number
-of operands, the list of implicit register uses and defs, whether the
-instruction has certain target-independent properties (accesses memory, is
-commutable, etc), and holds any target-specific flags.
+supported by the target. Descriptions define things like the mnemonic for
+the opcode, the number of operands, the list of implicit register uses and defs,
+whether the instruction has certain target-independent properties (accesses
+memory, is commutable, etc), and holds any target-specific flags.
The ``TargetFrameInfo`` class
-----------------------------
.. code-block:: llvm
define i32 @test(i32 %X, i32 %Y) {
- %Z = udiv i32 %X, %Y
+ %Z = sdiv i32 %X, %Y
ret i32 %Z
}
-The X86 instruction selector produces this machine code for the ``div`` and
-``ret`` (use "``llc X.bc -march=x86 -print-machineinstrs``" to get this):
+The X86 instruction selector might produce this machine code for the ``div`` and
+``ret``:
.. code-block:: llvm
%EAX = mov %reg1026 ;; 32-bit return value goes in EAX
ret
-By the end of code generation, the register allocator has coalesced the
-registers and deleted the resultant identity moves producing the following
+By the end of code generation, the register allocator would coalesce the
+registers and delete the resultant identity moves producing the following
code:
.. code-block:: llvm
that prints out a directive for each method (e.g. ``EmitValue -> .byte``), but
MCObjectStreamer implements a full assembler.
+For target specific directives, the MCStreamer has a MCTargetStreamer instance.
+Each target that needs it defines a class that inherits from it and is a lot
+like MCStreamer itself: It has one method per directive and two classes that
+inherit from it, a target object streamer and a target asm streamer. The target
+asm streamer just prints it (``emitFnStart -> .fnstrart``), and the object
+streamer implement the assembler logic for it.
+
+To make llvm use these classes, the target initialization must call
+TargetRegistry::RegisterAsmStreamer and TargetRegistry::RegisterMCObjectStreamer
+passing callbacks that allocate the corresponding target streamer and pass it
+to createAsmStreamer or to the appropriate object streamer constructor.
+
The ``MCContext`` class
-----------------------
are used to manipulate the input immediate (in this case, take the high or low
16-bits of the immediate).
+* When using the 'Pat' class to map a pattern to an instruction that has one
+ or more complex operands (like e.g. `X86 addressing mode`_), the pattern may
+ either specify the operand as a whole using a ``ComplexPattern``, or else it
+ may specify the components of the complex operand separately. The latter is
+ done e.g. for pre-increment instructions by the PowerPC back end:
+
+ ::
+
+ def STWU : DForm_1<37, (outs ptr_rc:$ea_res), (ins GPRC:$rS, memri:$dst),
+ "stwu $rS, $dst", LdStStoreUpd, []>,
+ RegConstraint<"$dst.reg = $ea_res">, NoEncode<"$ea_res">;
+
+ def : Pat<(pre_store GPRC:$rS, ptr_rc:$ptrreg, iaddroff:$ptroff),
+ (STWU GPRC:$rS, iaddroff:$ptroff, ptr_rc:$ptrreg)>;
+
+ Here, the pair of ``ptroff`` and ``ptrreg`` operands is matched onto the
+ complex operand ``dst`` of class ``memri`` in the ``STWU`` instruction.
+
* While the system does automate a lot, it still allows you to write custom C++
code to match special cases if there is something that is hard to
express.
particular class. For instance, in the X86 architecture, some virtuals can only
be allocated to 8 bit registers. A register class is described by
``TargetRegisterClass`` objects. To discover if a virtual register is
-compatible with a given physical, this code can be used:</p>
+compatible with a given physical, this code can be used:
.. code-block:: c++
===============================
Though you're probably reading this because you want to write or maintain a
-compiler backend, LLVM also fully supports building a native assemblers too.
+compiler backend, LLVM also fully supports building a native assembler.
We've tried hard to automate the generation of the assembler from the .td files
(in particular the instruction syntax and encodings), which means that a large
part of the manual and repetitive data entry can be factored and shared with the
def : MnemonicAlias<"pushf", "pushfq">, Requires<[In64BitMode]>;
def : MnemonicAlias<"pushf", "pushfl">, Requires<[In32BitMode]>;
-In this example, the mnemonic gets mapped into different a new one depending on
+In this example, the mnemonic gets mapped into a different one depending on
the current instruction set.
Instruction Aliases
:raw-html:`<th>Feature</th>`
:raw-html:`<th>ARM</th>`
:raw-html:`<th>Hexagon</th>`
-:raw-html:`<th>MBlaze</th>`
:raw-html:`<th>MSP430</th>`
:raw-html:`<th>Mips</th>`
:raw-html:`<th>NVPTX</th>`
:raw-html:`<th>PowerPC</th>`
:raw-html:`<th>Sparc</th>`
+:raw-html:`<th>SystemZ</th>`
:raw-html:`<th>X86</th>`
:raw-html:`<th>XCore</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="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="yes"></td> <!-- NVPTX -->`
:raw-html:`<td class="yes"></td> <!-- PowerPC -->`
:raw-html:`<td class="yes"></td> <!-- Sparc -->`
+:raw-html:`<td class="yes"></td> <!-- SystemZ -->`
:raw-html:`<td class="yes"></td> <!-- X86 -->`
-:raw-html:`<td class="unknown"></td> <!-- XCore -->`
+:raw-html:`<td class="yes"></td> <!-- XCore -->`
:raw-html:`</tr>`
: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> <!-- 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> <!-- NVPTX -->`
:raw-html:`<td class="no"></td> <!-- PowerPC -->`
:raw-html:`<td class="no"></td> <!-- Sparc -->`
+:raw-html:`<td class="yes"></td> <!-- SystemZ -->`
:raw-html:`<td class="yes"></td> <!-- X86 -->`
:raw-html:`<td class="no"></td> <!-- XCore -->`
: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> <!-- 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="na"></td> <!-- NVPTX -->`
:raw-html:`<td class="no"></td> <!-- PowerPC -->`
+:raw-html:`<td class="yes"></td> <!-- SystemZ -->`
:raw-html:`<td class="no"></td> <!-- Sparc -->`
:raw-html:`<td class="yes"></td> <!-- X86 -->`
-:raw-html:`<td class="no"></td> <!-- XCore -->`
+:raw-html:`<td class="yes"></td> <!-- XCore -->`
:raw-html:`</tr>`
: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="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="yes"></td> <!-- NVPTX -->`
:raw-html:`<td class="yes"></td> <!-- PowerPC -->`
:raw-html:`<td class="unknown"></td> <!-- Sparc -->`
+:raw-html:`<td class="yes"></td> <!-- SystemZ -->`
:raw-html:`<td class="yes"></td> <!-- X86 -->`
-:raw-html:`<td class="unknown"></td> <!-- XCore -->`
+:raw-html:`<td class="yes"></td> <!-- XCore -->`
:raw-html:`</tr>`
: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> <!-- 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="na"></td> <!-- NVPTX -->`
:raw-html:`<td class="yes"></td> <!-- PowerPC -->`
:raw-html:`<td class="unknown"></td> <!-- Sparc -->`
+:raw-html:`<td class="yes"></td> <!-- SystemZ -->`
:raw-html:`<td class="yes"></td> <!-- X86 -->`
-:raw-html:`<td class="unknown"></td> <!-- XCore -->`
+:raw-html:`<td class="no"></td> <!-- XCore -->`
:raw-html:`</tr>`
: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> <!-- 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="na"></td> <!-- NVPTX -->`
:raw-html:`<td class="no"></td> <!-- PowerPC -->`
:raw-html:`<td class="no"></td> <!-- Sparc -->`
+:raw-html:`<td class="yes"></td> <!-- SystemZ -->`
:raw-html:`<td class="yes"></td> <!-- X86 -->`
:raw-html:`<td class="no"></td> <!-- XCore -->`
: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="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="no"></td> <!-- NVPTX -->`
:raw-html:`<td class="yes"></td> <!-- PowerPC -->`
:raw-html:`<td class="unknown"></td> <!-- Sparc -->`
+:raw-html:`<td class="no"></td> <!-- SystemZ -->`
:raw-html:`<td class="yes"></td> <!-- X86 -->`
-:raw-html:`<td class="unknown"></td> <!-- XCore -->`
+:raw-html:`<td class="no"></td> <!-- XCore -->`
:raw-html:`</tr>`
: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> <!-- 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> <!-- NVPTX -->`
:raw-html:`<td class="no"></td> <!-- PowerPC -->`
:raw-html:`<td class="no"></td> <!-- Sparc -->`
+:raw-html:`<td class="no"></td> <!-- SystemZ -->`
:raw-html:`<td class="partial"><a href="#feat_segstacks_x86">*</a></td> <!-- X86 -->`
:raw-html:`<td class="no"></td> <!-- XCore -->`
:raw-html:`</tr>`
This box indicates whether the target supports guaranteed tail calls. These are
calls marked "`tail <LangRef.html#i_call>`_" and use the fastcc calling
-convention. Please see the `tail call section more more details`_.
+convention. Please see the `tail call section`_ for more details.
.. _feat_segstacks:
object files are not marked the way the gold linker expects, but simple Go
programs can be built by dragonegg.
-.. _tail call section more more details:
+.. _tail call section:
Tail call optimization
----------------------
* Option ``-tailcallopt`` is enabled.
-* Platform specific constraints are met.
+* Platform-specific constraints are met.
x86/x86-64 constraints:
projects / oota-llvm.git / blobdiff