diff options
Diffstat (limited to 'docs/WritingAnLLVMBackend.html')
| -rw-r--r-- | docs/WritingAnLLVMBackend.html | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/docs/WritingAnLLVMBackend.html b/docs/WritingAnLLVMBackend.html index 7576d490d7..0ad472cb92 100644 --- a/docs/WritingAnLLVMBackend.html +++ b/docs/WritingAnLLVMBackend.html @@ -32,6 +32,7 @@ <li><a href="#InstructionSet">Instruction Set</a> <ul> <li><a href="#operandMapping">Instruction Operand Mapping</a></li> + <li><a href="#relationMapping">Instruction Relation Mapping</a></li> <li><a href="#implementInstr">Implement a subclass of TargetInstrInfo</a></li> <li><a href="#branchFolding">Branch Folding and If Conversion</a></li> </ul></li> @@ -1259,6 +1260,29 @@ the <tt>rd</tt>, <tt>rs1</tt>, and <tt>rs2</tt> fields respectively. <!-- ======================================================================= --> <h3> + <a name="relationMapping">Instruction Relation Mapping</a> +</h3> + +<div> + +<p> +This TableGen feature is used to relate instructions with each other. It is +particularly useful when you have multiple instruction formats and need to +switch between them after instruction selection. This entire feature is driven +by relation models which can be defined in <tt>XXXInstrInfo.td</tt> files +according to the target-specific instruction set. Relation models are defined +using <tt>InstrMapping</tt> class as a base. TableGen parses all the models +and generates instruction relation maps using the specified information. +Relation maps are emitted as tables in the <tt>XXXGenInstrInfo.inc</tt> file +along with the functions to query them. For the detailed information on how to +use this feature, please refer to +<a href="HowToUseInstrMappings.html">How to add Instruction Mappings</a> +document. +</p> +</div> + +<!-- ======================================================================= --> +<h3> <a name="implementInstr">Implement a subclass of </a> <a href="CodeGenerator.html#targetinstrinfo">TargetInstrInfo</a> </h3> |