diff options
author | Andrew Trick <atrick@apple.com> | 2014-02-26 22:07:26 +0000 |
---|---|---|
committer | Andrew Trick <atrick@apple.com> | 2014-02-26 22:07:26 +0000 |
commit | eaf8a32859c0c0d485907785bb6b4c1426ed42dd (patch) | |
tree | 2f6b58101ae1a7e48c69d24367827b4f51e00415 /lib/CodeGen/RegAllocGreedy.cpp | |
parent | 692c94c1c9b5642cecb8fc7b6fa5ce3145b70ff1 (diff) | |
download | llvm-eaf8a32859c0c0d485907785bb6b4c1426ed42dd.tar.gz llvm-eaf8a32859c0c0d485907785bb6b4c1426ed42dd.tar.bz2 llvm-eaf8a32859c0c0d485907785bb6b4c1426ed42dd.tar.xz |
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.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202304 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen/RegAllocGreedy.cpp')
-rw-r--r-- | lib/CodeGen/RegAllocGreedy.cpp | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/lib/CodeGen/RegAllocGreedy.cpp b/lib/CodeGen/RegAllocGreedy.cpp index 19a9e3182e..6e6a594479 100644 --- a/lib/CodeGen/RegAllocGreedy.cpp +++ b/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 |