[PATCH] D29678: [Tablegen/DAG Debug] - Instrumenting table gen DAGGenISelDAG to allow printing selected patterns(and their sources) during ISEL

[Aditya Nandakumar via Phabricator via llvm-commits]

aditya_nandakumar created this revision.
Herald added subscribers: igorb, mgorny, aemerson.

To help assist in debugging ISEL or to prioritize GlobalISel backend work, this patch adds two more tables to <Target>GenISelDAGISel.inc - one which contains the patterns that are used during selection (The text comment //Src and //Dst comment  you see in MatcherTable for each of the MorphNode and EmitNode cases.
It adds another Tablegen OpcodeType called OPC_Coverage. We encode the offset of the pattern (in the table) with OPC_Coverage.
It also modifies the CheckComplexPattern to also print the ComplexPattern that returned true.
Sometimes, due to several layers of defm instantiations, to make it easier to identify where a particular pattern came from, the source locations have also been encoded in another table. This would get printed as

COMPLEX_PATTERN: SelectNegArithImmed
MORPHTO: (add:i32 GPR32:i32:$Rn, neg_addsub_shifted_imm32:i32:$imm) -> (SUBSWri:i32:i32 GPR32:i32:$Rn, neg_addsub_shifted_imm32:i32:$imm)
INCLUDED: /Volumes/Data/workspace/gpu/compiler_checkouts/open_source/llvm/lib/Target/AArch64/AArch64InstrInfo.td:659
.....

It's currently enabled through CMAKE variable DAG_PRINT_USED_ISEL_PATTERNS which passes a -instrument-coverage flag to table gen for emitting the *GenDAGISel.inc file.
This information can also be used (with a python script which greps/counts patterns) for building a test-suite(such as llvm-test-suite) and see which instructions/patterns need to be selected (say for global isel work prioritization) and can also print the tablegen emitted patterns that are unused during the compilation of the llvm-test-suite.

Looking forward to feedback.


Repository:
  rL LLVM

https://reviews.llvm.org/D29678

Files:
  CMakeLists.txt
  include/llvm/CodeGen/SelectionDAGISel.h
  lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
  lib/Target/AArch64/CMakeLists.txt
  utils/TableGen/DAGISelMatcherEmitter.cpp

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