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authorTom Stellard <thomas.stellard@amd.com>2013-06-25 21:22:09 +0000
committerTom Stellard <thomas.stellard@amd.com>2013-06-25 21:22:09 +0000
commit898b9f020d1089f679d1b1939fd6aafa9de4b411 (patch)
tree7e7627cb6da2fad8f7d9f5bc150a9860d208615f /docs
parent34eb2406b41854fc8df688fca7c0129f77d768f7 (diff)
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TableGen: Generate a function for getting operand indices based on their defined names
This patch modifies TableGen to generate a function in ${TARGET}GenInstrInfo.inc called getNamedOperandIdx(), which can be used to look up indices for operands based on their names. In order to activate this feature for an instruction, you must set the UseNamedOperandTable bit. For example, if you have an instruction like: def ADD : TargetInstr <(outs GPR:$dst), (ins GPR:$src0, GPR:$src1)>; You can look up the operand indices using the new function, like this: Target::getNamedOperandIdx(Target::ADD, Target::OpName::dst) => 0 Target::getNamedOperandIdx(Target::ADD, Target::OpName::src0) => 1 Target::getNamedOperandIdx(Target::ADD, Target::OpName::src1) => 2 The operand names are case sensitive, so $dst and $DST are considered different operands. This change is useful for R600 which has instructions with a large number of operands, many of which model single bit instruction configuration values. These configuration bits are common across most instructions, but may have a different operand index depending on the instruction type. It is useful to have a convenient way to look up the operand indices, so these bits can be generically set on any instruction. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184879 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'docs')
-rw-r--r--docs/WritingAnLLVMBackend.rst41
1 files changed, 41 insertions, 0 deletions
diff --git a/docs/WritingAnLLVMBackend.rst b/docs/WritingAnLLVMBackend.rst
index a03a5e4..9e3cb9e 100644
--- a/docs/WritingAnLLVMBackend.rst
+++ b/docs/WritingAnLLVMBackend.rst
@@ -911,6 +911,47 @@ format instructions will bind the operands to the ``rd``, ``rs1``, and ``rs2``
fields. This results in the ``XNORrr`` instruction binding ``$dst``, ``$b``,
and ``$c`` operands to the ``rd``, ``rs1``, and ``rs2`` fields respectively.
+TableGen will also generate a function called getNamedOperandIdx() which
+can be used to look up an operand's index in a MachineInstr based on its
+TableGen name. Setting the UseNamedOperandTable bit in an instruction's
+TableGen definition will add all of its operands to an enumeration in the
+llvm::XXX:OpName namespace and also add an entry for it into the OperandMap
+table, which can be queried using getNamedOperandIdx()
+
+.. code-block:: llvm
+
+ int DstIndex = SP::getNamedOperandIdx(SP::XNORrr, SP::OpName::dst); // => 0
+ int BIndex = SP::getNamedOperandIdx(SP::XNORrr, SP::OpName::b); // => 1
+ int CIndex = SP::getNamedOperandIdx(SP::XNORrr, SP::OpName::c); // => 2
+ int DIndex = SP::getNamedOperandIdx(SP::XNORrr, SP::OpName::d); // => -1
+
+ ...
+
+The entries in the OpName enum are taken verbatim from the TableGen definitions,
+so operands with lowercase names will have lower case entries in the enum.
+
+To include the getNamedOperandIdx() function in your backend, you will need
+to define a few preprocessor macros in XXXInstrInfo.cpp and XXXInstrInfo.h.
+For example:
+
+XXXInstrInfo.cpp:
+
+.. code-block:: c++
+
+ #define GET_INSTRINFO_NAMED_OPS // For getNamedOperandIdx() function
+ #include "XXXGenInstrInfo.inc"
+
+XXXInstrInfo.h:
+
+.. code-block:: c++
+
+ #define GET_INSTRINFO_OPERAND_ENUM // For OpName enum
+ #include "XXXGenInstrInfo.inc"
+
+ namespace XXX {
+ int16_t getNamedOperandIdx(uint16_t Opcode, uint16_t NamedIndex);
+ } // End namespace XXX
+
Instruction Relation Mapping
----------------------------