From bfebefca9f4b3bae066ad26da532060b837e0a16 Mon Sep 17 00:00:00 2001 From: James Molloy Date: Tue, 15 Dec 2015 09:24:01 +0000 Subject: [PATCH] [PassManagerBuilder] Add a few more scalar optimization passes This patch does two things: 1. mem2reg is now run immediately after globalopt. Now that globalopt can localize variables more aggressively, it makes sense to lower them to SSA form earlier rather than later so they can benefit from the full set of optimization passes. 2. More scalar optimizations are run after the loop optimizations in LTO mode. The loop optimizations (especially indvars) can clean up scalar code sufficiently to make it worthwhile running more scalar passes. I've particularly added SCCP here as it isn't run anywhere else in the LTO pass pipeline. Mem2reg is super cheap and shouldn't affect compilation time at all. The rest of the added passes are in the LTO pipeline only so doesn't affect the vast majority of compilations, just the link step. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@255634 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/IPO/PassManagerBuilder.cpp | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/lib/Transforms/IPO/PassManagerBuilder.cpp b/lib/Transforms/IPO/PassManagerBuilder.cpp index b8d1b7e78e3..6f709937f86 100644 --- a/lib/Transforms/IPO/PassManagerBuilder.cpp +++ b/lib/Transforms/IPO/PassManagerBuilder.cpp @@ -220,6 +220,8 @@ void PassManagerBuilder::populateModulePassManager( MPM.add(createIPSCCPPass()); // IP SCCP MPM.add(createGlobalOptimizerPass()); // Optimize out global vars + // Promote any localized global vars + MPM.add(createPromoteMemoryToRegisterPass()); MPM.add(createDeadArgEliminationPass()); // Dead argument elimination @@ -489,6 +491,8 @@ void PassManagerBuilder::addLTOOptimizationPasses(legacy::PassManagerBase &PM) { // Now that we internalized some globals, see if we can hack on them! PM.add(createFunctionAttrsPass()); // Add norecurse if possible. PM.add(createGlobalOptimizerPass()); + // Promote any localized global vars. + PM.add(createPromoteMemoryToRegisterPass()); // Linking modules together can lead to duplicated global constants, only // keep one copy of each constant. @@ -554,6 +558,15 @@ void PassManagerBuilder::addLTOOptimizationPasses(legacy::PassManagerBase &PM) { PM.add(createLoopVectorizePass(true, LoopVectorize)); + // Now that we've optimized loops (in particular loop induction variables), + // we may have exposed more scalar opportunities. Run parts of the scalar + // optimizer again at this point. + PM.add(createInstructionCombiningPass()); // Initial cleanup + PM.add(createCFGSimplificationPass()); // if-convert + PM.add(createSCCPPass()); // Propagate exposed constants + PM.add(createInstructionCombiningPass()); // Clean up again + PM.add(createBitTrackingDCEPass()); + // More scalar chains could be vectorized due to more alias information if (RunSLPAfterLoopVectorization) if (SLPVectorize) -- 2.34.1