LLVM backend for 6502
Go to file
Karthik Bhat 52610d84ad Add a new pass "Loop Interchange"
This pass interchanges loops to provide a more cache-friendly memory access.

For e.g. given a loop like -
  for(int i=0;i<N;i++)
    for(int j=0;j<N;j++)
      A[j][i] = A[j][i]+B[j][i];

is interchanged to -
  for(int j=0;j<N;j++)
    for(int i=0;i<N;i++)
      A[j][i] = A[j][i]+B[j][i];

This pass is currently disabled by default.

To give a brief introduction it consists of 3 stages-

LoopInterchangeLegality : Checks the legality of loop interchange based on Dependency matrix.
LoopInterchangeProfitability: A very basic heuristic has been added to check for profitibility. This will evolve over time.
LoopInterchangeTransform : Which does the actual transform.

LNT Performance tests shows improvement in Polybench/linear-algebra/kernels/mvt and Polybench/linear-algebra/kernels/gemver becnmarks.

TODO:
1) Add support for reductions and lcssa phi.
2) Improve profitability model.
3) Improve loop selection algorithm to select best loop for interchange. Currently the innermost loop is selected for interchange.
4) Improve compile time regression found in llvm lnt due to this pass.
5) Fix issues in Dependency Analysis module.

A special thanks to Hal for reviewing this code.
Review: http://reviews.llvm.org/D7499




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231458 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-06 10:11:25 +00:00
autoconf
bindings Go bindings: use MDNode::replaceAllUsesWith instead of MDTuple::replaceAllUsesWith. 2015-03-05 22:55:38 +00:00
cmake
docs All FileCheck directives allow patterns. 2015-03-05 23:04:26 +00:00
examples
include Add a new pass "Loop Interchange" 2015-03-06 10:11:25 +00:00
lib Add a new pass "Loop Interchange" 2015-03-06 10:11:25 +00:00
projects
test Add a new pass "Loop Interchange" 2015-03-06 10:11:25 +00:00
tools
unittests Fix -Woverflow warning in unittest. 2015-03-05 14:43:15 +00:00
utils TableGen: Initialize ErrorInfo to ~0ULL in the MatchInstructionImpl 2015-03-05 19:46:55 +00:00
.arcconfig
.clang-format
.clang-tidy
.gitignore
CMakeLists.txt
CODE_OWNERS.TXT [CODE_OWNERS] Change the ownership of register allocators. 2015-03-05 22:15:17 +00:00
configure
CREDITS.TXT
LICENSE.TXT
llvm.spec.in
LLVMBuild.txt
Makefile
Makefile.common
Makefile.config.in
Makefile.rules
README.txt

Low Level Virtual Machine (LLVM)
================================

This directory and its subdirectories contain source code for LLVM,
a toolkit for the construction of highly optimized compilers,
optimizers, and runtime environments.

LLVM is open source software. You may freely distribute it under the terms of
the license agreement found in LICENSE.txt.

Please see the documentation provided in docs/ for further
assistance with LLVM, and in particular docs/GettingStarted.rst for getting
started with LLVM and docs/README.txt for an overview of LLVM's
documentation setup.

If you're writing a package for LLVM, see docs/Packaging.rst for our
suggestions.