From dd9e637acaf0f288f3e281559c9a74ae4a9f15e3 Mon Sep 17 00:00:00 2001 From: Adam Nemet Date: Mon, 29 Feb 2016 20:35:11 +0000 Subject: [PATCH] Enable LoopLoadElimination by default Summary: I re-benchmarked this and results are similar to original results in D13259: On ARM64: SingleSource/Benchmarks/Polybench/linear-algebra/solvers/dynprog -59.27% SingleSource/Benchmarks/Polybench/stencils/adi -19.78% On x86: SingleSource/Benchmarks/Polybench/linear-algebra/solvers/dynprog -27.14% And of course the original ~20% gain on SPECint_2006/456.hmmer with Loop Distribution. In terms of compile time, there is ~5% increase on both SingleSource/Benchmarks/Misc/oourafft and SingleSource/Benchmarks/Linkpack/linkpack-pc. These are both very tiny loop-intensive programs where SCEV computations dominates compile time. The reason that time spent in SCEV increases has to do with the design of the old pass manager. If a transform pass does not preserve an analysis we *invalidate* the analysis even if there was *no* modification made by the transform pass. This means that currently we don't take advantage of LLE and LV sharing the same analysis (LAA) and unfortunately we recompute LAA *and* SCEV for LLE. (There should be a way to work around this limitation in the case of SCEV and LAA since both compute things on demand and internally cache their result. Thus we could pretend that transform passes preserve these analyses and manually invalidate them upon actual modification. On the other hand the new pass manager is supposed to solve so I am not sure if this is worthwhile.) Reviewers: hfinkel, dberlin Subscribers: dberlin, reames, mssimpso, aemerson, joker.eph, llvm-commits Differential Revision: http://reviews.llvm.org/D16300 llvm-svn: 262250 --- llvm/lib/Transforms/IPO/PassManagerBuilder.cpp | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp index c490e06..a659cc6 100644 --- a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp +++ b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp @@ -104,8 +104,8 @@ static cl::opt EnableNonLTOGlobalsModRef( "Enable the GlobalsModRef AliasAnalysis outside of the LTO pipeline.")); static cl::opt EnableLoopLoadElim( - "enable-loop-load-elim", cl::init(false), cl::Hidden, - cl::desc("Enable the new, experimental LoopLoadElimination Pass")); + "enable-loop-load-elim", cl::init(true), cl::Hidden, + cl::desc("Enable the LoopLoadElimination Pass")); static cl::opt RunPGOInstrGen( "profile-generate", cl::init(""), cl::Hidden, -- 2.7.4