mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2025-02-01 05:01:59 +01:00
69f2d6f1bb
Summary:
The MatchDag structure is a representation of the checks that need to be
performed and the dependencies that limit when they can happen.
There are two kinds of node in the MatchDag:
* Instrs - Represent a MachineInstr
* Predicates - Represent a check that needs to be performed (i.e. opcode, is register, same machine operand, etc.)
and two kinds of edges:
* (Traversal) Edges - Represent a register that can be traversed to find one instr from another
* Predicate Dependency Edges - Indicate that a predicate requires a piece of information to be tested.
For example, the matcher:
(match (MOV $t, $s),
(MOV $d, $t))
with MOV declared as an instruction of the form:
%dst = MOV %src1
becomes the following MatchDag with the following instruction nodes:
__anon0_0 // $t=getOperand(0), $s=getOperand(1)
__anon0_1 // $d=getOperand(0), $t=getOperand(1)
traversal edges:
__anon0_1[src1] --[t]--> __anon0_0[dst]
predicate nodes:
<<$mi.getOpcode() == MOV>>:$__anonpred0_2
<<$mi.getOpcode() == MOV>>:$__anonpred0_3
and predicate dependencies:
__anon0_0 ==> __anonpred0_2[mi]
__anon0_0 ==> __anonpred0_3[mi]
The result of this parse is currently unused but can be tested
using -gicombiner-stop-after-parse as done in parse-match-pattern.td. The
dump for testing includes a graphviz format dump to allow the rule to be
viewed visually.
Later on, these MatchDag's will be used to generate code and to build an
efficient decision tree.
Reviewers: volkan, bogner
Reviewed By: volkan
Subscribers: arsenm, mgorny, mgrang, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69077