From 52a00936b4862096ae073c8c9391a3bae44c2e8a Mon Sep 17 00:00:00 2001 From: Andrew Trick Date: Wed, 26 Feb 2014 22:07:26 +0000 Subject: Add a limit to the heuristic that register allocates instructions in local order. This handles pathological cases in which we see 2x increase in spill code for large blocks (~50k instructions). I don't have a unit test for this behavior. Fixes rdar://16072279. llvm-svn: 202304 --- llvm/lib/CodeGen/RegAllocGreedy.cpp | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'llvm/lib/CodeGen/RegAllocGreedy.cpp') diff --git a/llvm/lib/CodeGen/RegAllocGreedy.cpp b/llvm/lib/CodeGen/RegAllocGreedy.cpp index 19a9e3182e7..6e6a594479e 100644 --- a/llvm/lib/CodeGen/RegAllocGreedy.cpp +++ b/llvm/lib/CodeGen/RegAllocGreedy.cpp @@ -454,12 +454,18 @@ void RAGreedy::enqueue(PQueue &CurQueue, LiveInterval *LI) { // everything else has been allocated. Prio = Size; } else { - if (ExtraRegInfo[Reg].Stage == RS_Assign && !LI->empty() && + // Giant live ranges fall back to the global assignment heuristic, which + // prevents excessive spilling in pathological cases. + bool ReverseLocal = TRI->reverseLocalAssignment(); + bool ForceGlobal = !ReverseLocal && + (Size / SlotIndex::InstrDist) > (2 * MRI->getRegClass(Reg)->getNumRegs()); + + if (ExtraRegInfo[Reg].Stage == RS_Assign && !ForceGlobal && !LI->empty() && LIS->intervalIsInOneMBB(*LI)) { // Allocate original local ranges in linear instruction order. Since they // are singly defined, this produces optimal coloring in the absence of // global interference and other constraints. - if (!TRI->reverseLocalAssignment()) + if (!ReverseLocal) Prio = LI->beginIndex().getInstrDistance(Indexes->getLastIndex()); else { // Allocating bottom up may allow many short LRGs to be assigned first -- cgit v1.2.3