================
@@ -30,290 +25,284 @@ Before you invest a significant amount of effort into a
non-trivial extension,
existing infrastructure, or if maybe someone else is already working on
it. You will save yourself a lot of time and effort by doing so.
-.. _intrinsic function:
+(intrinsic-function)=
-Adding a new intrinsic function
-===============================
+## Adding a new intrinsic function
Adding a new intrinsic function to LLVM is much easier than adding a new
-instruction. Almost all extensions to LLVM should start as an intrinsic
+instruction. Almost all extensions to LLVM should start as an intrinsic
function and then be turned into an instruction if warranted.
-#. ``llvm/docs/LangRef.html``:
+1. `llvm/docs/LangRef.html`:
- Document the intrinsic. Decide whether it is code generator specific and
- what the restrictions are. Talk to other people about it so that you are
+ Document the intrinsic. Decide whether it is code generator specific and
+ what the restrictions are. Talk to other people about it so that you are
sure it's a good idea.
-#. ``llvm/include/llvm/IR/Intrinsics*.td``:
+2. `llvm/include/llvm/IR/Intrinsics*.td`:
- Add an entry for your intrinsic. Describe its memory access
+ Add an entry for your intrinsic. Describe its memory access
characteristics for optimization (this controls whether it will be
DCE'd, CSE'd, etc). If any arguments need to be immediates, these
must be indicated with the ImmArg property. Note that any intrinsic
- using one of the ``llvm_any*_ty`` types for an argument or return
- type will be deemed by ``tblgen`` as overloaded and the
+ using one of the `llvm_any*_ty` types for an argument or return
+ type will be deemed by `tblgen` as overloaded and the
corresponding suffix will be required on the intrinsic's name.
-#. ``llvm/lib/Analysis/ConstantFolding.cpp``:
+3. `llvm/lib/Analysis/ConstantFolding.cpp`:
If it is possible to constant fold your intrinsic, add support for it in the
- ``canConstantFoldCallTo`` and ``ConstantFoldCall`` functions.
+ `canConstantFoldCallTo` and `ConstantFoldCall` functions.
-#. ``llvm/test/*``:
+4. `llvm/test/*`:
Add test cases for your intrinsic to the test suite
Once the intrinsic has been added to the system, you must add code generator
-support for it. Generally you must do the following steps:
+support for it. Generally you must do the following steps:
Add support to the .td file for the target(s) of your choice in
-``lib/Target/*/*.td``.
+`lib/Target/*/*.td`.
- This is usually a matter of adding a pattern to the .td file that matches the
- intrinsic, though it may obviously require adding the instructions you want
to
- generate as well. There are lots of examples in the PowerPC and X86 backends
- to follow.
+> This is usually a matter of adding a pattern to the .td file that matches the
+> intrinsic, though it may obviously require adding the instructions you want
to
+> generate as well. There are lots of examples in the PowerPC and X86 backends
+> to follow.
-Adding a new SelectionDAG node
-==============================
+## Adding a new SelectionDAG node
As with intrinsics, adding a new SelectionDAG node to LLVM is much easier than
-adding a new instruction. New nodes are often added to help represent
-instructions common to many targets. These nodes often map to an LLVM
-instruction (add, sub) or intrinsic (byteswap, population count). In other
+adding a new instruction. New nodes are often added to help represent
+instructions common to many targets. These nodes often map to an LLVM
+instruction (add, sub) or intrinsic (byteswap, population count). In other
cases, new nodes have been added to allow many targets to perform a common task
(converting between floating point and integer representation) or capture more
complicated behavior in a single node (rotate).
-#. ``include/llvm/CodeGen/ISDOpcodes.h``:
-
- Add an enum value for the new SelectionDAG node.
+01. `include/llvm/CodeGen/ISDOpcodes.h`:
-#. ``lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp``:
+ Add an enum value for the new SelectionDAG node.
- Add code to print the node to ``getOperationName``. If your new node can be
- evaluated at compile time when given constant arguments (such as an add of a
- constant with another constant), find the ``getNode`` method that takes the
- appropriate number of arguments, and add a case for your node to the switch
- statement that performs constant folding for nodes that take the same number
- of arguments as your new node.
+02. `lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp`:
-#. ``lib/CodeGen/SelectionDAG/LegalizeDAG.cpp``:
+ Add code to print the node to `getOperationName`. If your new node can be
+ evaluated at compile time when given constant arguments (such as an add of
a
+ constant with another constant), find the `getNode` method that takes the
+ appropriate number of arguments, and add a case for your node to the switch
+ statement that performs constant folding for nodes that take the same
number
+ of arguments as your new node.
- Add code to `legalize, promote, and expand
- <CodeGenerator.html#selectiondag_legalize>`_ the node as necessary. At a
- minimum, you will need to add a case statement for your node in
- ``LegalizeOp`` which calls LegalizeOp on the node's operands, and returns a
- new node if any of the operands changed as a result of being legalized. It
- is likely that not all targets supported by the SelectionDAG framework will
- natively support the new node. In this case, you must also add code in your
- node's case statement in ``LegalizeOp`` to Expand your node into simpler,
- legal operations. The case for ``ISD::UREM`` for expanding a remainder into
- a divide, multiply, and a subtract is a good example.
+03. `lib/CodeGen/SelectionDAG/LegalizeDAG.cpp`:
-#. ``lib/CodeGen/SelectionDAG/LegalizeDAG.cpp``:
+ Add code to [legalize, promote, and
+ expand](project:CodeGenerator.md#selectiondag-legalize-phase) the node as
+ necessary. At a minimum, you will need to add a case statement for your
node
+ in `LegalizeOp` which calls LegalizeOp on the node's operands, and returns
a
+ new node if any of the operands changed as a result of being legalized. It
+ is likely that not all targets supported by the SelectionDAG framework will
+ natively support the new node. In this case, you must also add code in your
+ node's case statement in `LegalizeOp` to Expand your node into simpler,
+ legal operations. The case for `ISD::UREM` for expanding a remainder into
+ a divide, multiply, and a subtract is a good example.
- If targets may support the new node being added only at certain sizes, you
- will also need to add code to your node's case statement in ``LegalizeOp``
- to Promote your node's operands to a larger size, and perform the correct
- operation. You will also need to add code to ``PromoteOp`` to do this as
- well. For a good example, see ``ISD::BSWAP``, which promotes its operand to
- a wider size, performs the byteswap, and then shifts the correct bytes right
- to emulate the narrower byteswap in the wider type.
+04. `lib/CodeGen/SelectionDAG/LegalizeDAG.cpp`:
-#. ``lib/CodeGen/SelectionDAG/LegalizeDAG.cpp``:
+ If targets may support the new node being added only at certain sizes, you
+ will also need to add code to your node's case statement in `LegalizeOp`
+ to Promote your node's operands to a larger size, and perform the correct
+ operation. You will also need to add code to `PromoteOp` to do this as
+ well. For a good example, see `ISD::BSWAP`, which promotes its operand to
+ a wider size, performs the byteswap, and then shifts the correct bytes
right
+ to emulate the narrower byteswap in the wider type.
- Add a case for your node in ``ExpandOp`` to teach the legalizer how to
- perform the action represented by the new node on a value that has been
split
- into high and low halves. This case will be used to support your node with
a
- 64-bit operand on a 32-bit target.
+05. `lib/CodeGen/SelectionDAG/LegalizeDAG.cpp`:
-#. ``lib/CodeGen/SelectionDAG/DAGCombiner.cpp``:
+ Add a case for your node in `ExpandOp` to teach the legalizer how to
+ perform the action represented by the new node on a value that has been
split
+ into high and low halves. This case will be used to support your node with
a
+ 64-bit operand on a 32-bit target.
- If your node can be combined with itself, or other existing nodes in a
- peephole-like fashion, add a visit function for it, and call that function
- from. There are several good examples for simple combines you can do;
- ``visitFABS`` and ``visitSRL`` are good starting places.
+06. `lib/CodeGen/SelectionDAG/DAGCombiner.cpp`:
-#. ``lib/Target/PowerPC/PPCISelLowering.cpp``:
+ If your node can be combined with itself, or other existing nodes in a
+ peephole-like fashion, add a visit function for it, and call that function
+ from. There are several good examples for simple combines you can do;
+ `visitFABS` and `visitSRL` are good starting places.
- Each target has an implementation of the ``TargetLowering`` class, usually
in
- its own file (although some targets include it in the same file as the
- DAGToDAGISel). The default behavior for a target is to assume that your new
- node is legal for all types that are legal for that target. If this target
- does not natively support your node, then tell the target to either Promote
- it (if it is supported at a larger type) or Expand it. This will cause the
- code you wrote in ``LegalizeOp`` above to decompose your new node into other
- legal nodes for this target.
+07. `lib/Target/PowerPC/PPCISelLowering.cpp`:
-#. ``include/llvm/Target/TargetSelectionDAG.td``:
+ Each target has an implementation of the `TargetLowering` class, usually in
+ its own file (although some targets include it in the same file as the
+ DAGToDAGISel). The default behavior for a target is to assume that your new
+ node is legal for all types that are legal for that target. If this target
+ does not natively support your node, then tell the target to either Promote
+ it (if it is supported at a larger type) or Expand it. This will cause the
+ code you wrote in `LegalizeOp` above to decompose your new node into other
+ legal nodes for this target.
- Most current targets supported by LLVM generate code using the DAGToDAG
- method, where SelectionDAG nodes are pattern matched to target-specific
- nodes, which represent individual instructions. In order for the targets to
- match an instruction to your new node, you must add a def for that node to
- the list in this file, with the appropriate type constraints. Look at
- ``add``, ``bswap``, and ``fadd`` for examples.
+08. `include/llvm/Target/TargetSelectionDAG.td`:
-#. ``lib/Target/PowerPC/PPCInstrInfo.td``:
+ Most current targets supported by LLVM generate code using the DAGToDAG
+ method, where SelectionDAG nodes are pattern matched to target-specific
+ nodes, which represent individual instructions. In order for the targets to
+ match an instruction to your new node, you must add a def for that node to
+ the list in this file, with the appropriate type constraints. Look at
+ `add`, `bswap`, and `fadd` for examples.
- Each target has a tablegen file that describes the target's instruction set.
- For targets that use the DAGToDAG instruction selection framework, add a
- pattern for your new node that uses one or more target nodes. Documentation
- for this is a bit sparse right now, but there are several decent examples.
- See the patterns for ``rotl`` in ``PPCInstrInfo.td``.
+09. `lib/Target/PowerPC/PPCInstrInfo.td`:
-#. TODO: document complex patterns.
+ Each target has a tablegen file that describes the target's instruction
set.
+ For targets that use the DAGToDAG instruction selection framework, add a
+ pattern for your new node that uses one or more target nodes. Documentation
+ for this is a bit sparse right now, but there are several decent examples.
+ See the patterns for `rotl` in `PPCInstrInfo.td`.
-#. ``llvm/test/CodeGen/*``:
+10. TODO: document complex patterns.
- Add test cases for your new node to the test suite.
- ``llvm/test/CodeGen/X86/bswap.ll`` is a good example.
+11. `llvm/test/CodeGen/*`:
-Adding a new instruction
-========================
+ Add test cases for your new node to the test suite.
+ `llvm/test/CodeGen/X86/bswap.ll` is a good example.
-.. warning::
+## Adding a new instruction
- Adding instructions changes the bitcode format, and it will take some effort
- to maintain compatibility with the previous version. Only add an instruction
- if it is absolutely necessary.
+:::{warning}
+Adding instructions changes the bitcode format, and it will take some effort
+to maintain compatibility with the previous version. Only add an instruction
+if it is absolutely necessary.
+:::
-#. ``llvm/include/llvm/IR/Instruction.def``:
+01. `llvm/include/llvm/IR/Instruction.def`:
----------------
rnk wrote:
It's just what rst2myst does for numbered lists beyond 10:
```
❯ cat build/t.md
#. a
#. a
#. a
#. a
#. a
#. a
#. a
#. a
#. a
#. a
#. a
#. a
#. a
#. a
#. a
#. a
#. a
#. a
#. a
#. a
#. a
❯ ../../venv/bin/rst2myst stream build/t.md
01. a
02. a
03. a
04. a
05. a
06. a
07. a
08. a
09. a
10. a
11. a
12. a
13. a
14. a
15. a
16. a
17. a
18. a
19. a
20. a
21. a
```
I removed the leading zeros and did space right padding.
https://github.com/llvm/llvm-project/pull/208798
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