From 8828c4ccd44cb49d13360cf86fd0b963f211f03f Mon Sep 17 00:00:00 2001 From: Jakob Stoklund Olesen Date: Fri, 10 Aug 2012 20:11:38 +0000 Subject: Include loop-carried dependencies when computing instr heights. When a trace ends with a back-edge, include PHIs in the loop header in the height computations. This makes the critical path through a loop more accurate by including the latencies of the last instructions in the loop. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161688 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/MachineTraceMetrics.cpp | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) (limited to 'lib/CodeGen/MachineTraceMetrics.cpp') diff --git a/lib/CodeGen/MachineTraceMetrics.cpp b/lib/CodeGen/MachineTraceMetrics.cpp index d0e6398..c6a6d58 100644 --- a/lib/CodeGen/MachineTraceMetrics.cpp +++ b/lib/CodeGen/MachineTraceMetrics.cpp @@ -931,17 +931,29 @@ computeInstrHeights(const MachineBasicBlock *MBB) { TBI.CriticalPath = 0; // Get dependencies from PHIs in the trace successor. - if (TBI.Succ) { - for (MachineBasicBlock::const_iterator - I = TBI.Succ->begin(), E = TBI.Succ->end(); + const MachineBasicBlock *Succ = TBI.Succ; + // If MBB is the last block in the trace, and it has a back-edge to the + // loop header, get loop-carried dependencies from PHIs in the header. For + // that purpose, pretend that all the loop header PHIs have height 0. + if (!Succ) + if (const MachineLoop *Loop = getLoopFor(MBB)) + if (MBB->isSuccessor(Loop->getHeader())) + Succ = Loop->getHeader(); + + if (Succ) { + for (MachineBasicBlock::const_iterator I = Succ->begin(), E = Succ->end(); I != E && I->isPHI(); ++I) { const MachineInstr *PHI = I; Deps.clear(); getPHIDeps(PHI, Deps, MBB, MTM.MRI); - if (!Deps.empty()) - if (pushDepHeight(Deps.front(), PHI, Cycles.lookup(PHI).Height, - Heights, MTM.ItinData, MTM.TII)) + if (!Deps.empty()) { + // Loop header PHI heights are all 0. + unsigned Height = TBI.Succ ? Cycles.lookup(PHI).Height : 0; + DEBUG(dbgs() << "pred\t" << Height << '\t' << *PHI); + if (pushDepHeight(Deps.front(), PHI, Height, + Heights, MTM.ItinData, MTM.TII)) addLiveIns(Deps.front().DefMI, Stack); + } } } -- cgit v1.1