From 35071a08470b56dff90697618682720df7d3896c Mon Sep 17 00:00:00 2001 From: Jakob Stoklund Olesen Date: Tue, 9 Mar 2010 00:59:48 +0000 Subject: [PATCH] Disable physical register coalescing when the number of live ranges for the physreg becomes ridiculously high. std::upper_bound may be log(N), but for sufficiently large live intervals, it becomes log(N)*cachemiss = a long long time. This patch improves coalescer time by 4500x for a function with 20000 function calls. The generated code is different, but not significantly worse - the allocator hints are almost as good as physreg coalescing anyway. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98023 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/SimpleRegisterCoalescing.cpp | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp index ce72b2fc148..d25df1d2ad8 100644 --- a/lib/CodeGen/SimpleRegisterCoalescing.cpp +++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp @@ -1671,8 +1671,20 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) { // density, do not join them, instead mark the physical register as its // allocation preference. LiveInterval &JoinVInt = SrcIsPhys ? DstInt : SrcInt; + LiveInterval &JoinPInt = SrcIsPhys ? SrcInt : DstInt; unsigned JoinVReg = SrcIsPhys ? DstReg : SrcReg; unsigned JoinPReg = SrcIsPhys ? SrcReg : DstReg; + + // Don't join with physregs that have a ridiculous number of live + // ranges. The data structure performance is really bad when that + // happens. + if (JoinPInt.ranges.size() > 1000) { + mri_->setRegAllocationHint(JoinVInt.reg, 0, JoinPReg); + ++numAborts; + DEBUG(dbgs() << "\tPhysical register too complicated, abort!\n"); + return false; + } + const TargetRegisterClass *RC = mri_->getRegClass(JoinVReg); unsigned Threshold = allocatableRCRegs_[RC].count() * 2; unsigned Length = li_->getApproximateInstructionCount(JoinVInt);