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Better comments to explain buffered/unbuffered processor resources. 

llvm-svn: 206625
This commit is contained in:
Andrew Trick 2014-04-18 17:35:08 +00:00
parent 762343da6c
commit 1766f93b35
1 changed files with 8 additions and 4 deletions
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12
llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
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@ -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