From 1766f93b359de14f75c705ab379c5c364592055a Mon Sep 17 00:00:00 2001 From: Andrew Trick Date: Fri, 18 Apr 2014 17:35:08 +0000 Subject: [PATCH] Better comments to explain buffered/unbuffered processor resources. llvm-svn: 206625 --- llvm/lib/CodeGen/ScheduleDAGInstrs.cpp | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp b/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp index 9c516c6edd98..4ac2a3c5bf06 100644 --- a/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp +++ b/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp @@ -699,10 +699,14 @@ void ScheduleDAGInstrs::initSUnits() { // Assign the Latency field of SU using target-provided information. SU->Latency = SchedModel.computeInstrLatency(SU->getInstr()); - // If this SUnit uses an unbuffered resource, mark it as such. - // These resources are used for in-order execution pipelines within an - // out-of-order core and are identified by BufferSize=1. BufferSize=0 is - // used for dispatch/issue groups and is not considered here. + // If this SUnit uses a reserved or unbuffered resource, mark it as such. + // + // Reserved resources block an instruction from issueing and stall the + // entire pipeline. These are identified by BufferSize=0. + // + // Unbuffered resources prevent execution of subsequeny instructions that + // require the same resources. This is used for in-order execution pipelines + // within an out-of-order core. These are identified by BufferSize=1. if (SchedModel.hasInstrSchedModel()) { const MCSchedClassDesc *SC = getSchedClass(SU); for (TargetSchedModel::ProcResIter