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[PBQP Regalloc] Pre-spill vregs that have no legal physregs.

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The PBQP::RegAlloc::MatrixMetadata class assumes that matrices have at least two
rows/columns (for the spill option plus at least one physreg). This patch
ensures that that invariant is met by pre-spilling vregs that have no physreg
options so that no node (and no corresponding edges) need be added to the PBQP
graph.

This fixes a bug in an out-of-tree target that was identified by Jonas Paulsson.
Thanks for tracking this down Jonas!



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227942 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Lang Hames 2015-02-03 06:14:06 +00:00
parent 56756c43cd
commit d54450ef63
2 changed files with 59 additions and 26 deletions
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2
include/llvm/CodeGen/RegAllocPBQP.h
View File

@ -309,6 +309,8 @@ public:
}
void handleAddNode(NodeId NId) {
assert(G.getNodeCosts(NId).getLength() > 1 &&
"PBQP Graph should not contain single or zero-option nodes");
G.getNodeMetadata(NId).setup(G.getNodeCosts(NId));
}
void handleRemoveNode(NodeId NId) {}

83
lib/CodeGen/RegAllocPBQP.cpp
View File

@ -126,7 +126,12 @@ private:
void findVRegIntervalsToAlloc(const MachineFunction &MF, LiveIntervals &LIS);
/// \brief Constructs an initial graph.
void initializeGraph(PBQPRAGraph &G);
void initializeGraph(PBQPRAGraph &G, VirtRegMap &VRM, Spiller &VRegSpiller);
/// \brief Spill the given VReg.
void spillVReg(unsigned VReg, SmallVectorImpl<unsigned> &NewIntervals,
MachineFunction &MF, LiveIntervals &LIS, VirtRegMap &VRM,
Spiller &VRegSpiller);
/// \brief Given a solved PBQP problem maps this solution back to a register
/// assignment.
@ -486,7 +491,8 @@ static bool isACalleeSavedRegister(unsigned reg, const TargetRegisterInfo &TRI,
return false;
}
void RegAllocPBQP::initializeGraph(PBQPRAGraph &G) {
void RegAllocPBQP::initializeGraph(PBQPRAGraph &G, VirtRegMap &VRM,
Spiller &VRegSpiller) {
MachineFunction &MF = G.getMetadata().MF;
LiveIntervals &LIS = G.getMetadata().LIS;
@ -494,7 +500,12 @@ void RegAllocPBQP::initializeGraph(PBQPRAGraph &G) {
const TargetRegisterInfo &TRI =
*G.getMetadata().MF.getSubtarget().getRegisterInfo();
for (auto VReg : VRegsToAlloc) {
std::vector<unsigned> Worklist(VRegsToAlloc.begin(), VRegsToAlloc.end());
while (!Worklist.empty()) {
unsigned VReg = Worklist.back();
Worklist.pop_back();
const TargetRegisterClass *TRC = MRI.getRegClass(VReg);
LiveInterval &VRegLI = LIS.getInterval(VReg);
@ -529,6 +540,16 @@ void RegAllocPBQP::initializeGraph(PBQPRAGraph &G) {
VRegAllowed.push_back(PReg);
}
// Check for vregs that have no allowed registers. These should be
// pre-spilled and the new vregs added to the worklist.
if (VRegAllowed.empty()) {
SmallVector<unsigned, 8> NewVRegs;
spillVReg(VReg, NewVRegs, MF, LIS, VRM, VRegSpiller);
for (auto NewVReg : NewVRegs)
Worklist.push_back(NewVReg);
continue;
}
PBQPRAGraph::RawVector NodeCosts(VRegAllowed.size() + 1, 0);
// Tweak cost of callee saved registers, as using then force spilling and
@ -545,6 +566,33 @@ void RegAllocPBQP::initializeGraph(PBQPRAGraph &G) {
}
}
void RegAllocPBQP::spillVReg(unsigned VReg,
SmallVectorImpl<unsigned> &NewIntervals,
MachineFunction &MF, LiveIntervals &LIS,
VirtRegMap &VRM, Spiller &VRegSpiller) {
VRegsToAlloc.erase(VReg);
LiveRangeEdit LRE(&LIS.getInterval(VReg), NewIntervals, MF, LIS, &VRM);
VRegSpiller.spill(LRE);
const TargetRegisterInfo &TRI = *MF.getSubtarget().getRegisterInfo();
(void)TRI;
DEBUG(dbgs() << "VREG " << PrintReg(VReg, &TRI) << " -> SPILLED (Cost: "
<< LRE.getParent().weight << ", New vregs: ");
// Copy any newly inserted live intervals into the list of regs to
// allocate.
for (LiveRangeEdit::iterator I = LRE.begin(), E = LRE.end();
I != E; ++I) {
const LiveInterval &LI = LIS.getInterval(*I);
assert(!LI.empty() && "Empty spill range.");
DEBUG(dbgs() << PrintReg(LI.reg, &TRI) << " ");
VRegsToAlloc.insert(LI.reg);
}
DEBUG(dbgs() << ")\n");
}
bool RegAllocPBQP::mapPBQPToRegAlloc(const PBQPRAGraph &G,
const PBQP::Solution &Solution,
VirtRegMap &VRM,
@ -573,28 +621,11 @@ bool RegAllocPBQP::mapPBQPToRegAlloc(const PBQPRAGraph &G,
assert(PReg != 0 && "Invalid preg selected.");
VRM.assignVirt2Phys(VReg, PReg);
} else {
VRegsToAlloc.erase(VReg);
SmallVector<unsigned, 8> NewSpills;
LiveRangeEdit LRE(&LIS.getInterval(VReg), NewSpills, MF, LIS, &VRM);
VRegSpiller.spill(LRE);
DEBUG(dbgs() << "VREG " << PrintReg(VReg, &TRI) << " -> SPILLED (Cost: "
<< LRE.getParent().weight << ", New vregs: ");
// Copy any newly inserted live intervals into the list of regs to
// allocate.
for (LiveRangeEdit::iterator I = LRE.begin(), E = LRE.end();
I != E; ++I) {
LiveInterval &LI = LIS.getInterval(*I);
assert(!LI.empty() && "Empty spill range.");
DEBUG(dbgs() << PrintReg(LI.reg, &TRI) << " ");
VRegsToAlloc.insert(LI.reg);
}
DEBUG(dbgs() << ")\n");
// We need another round if spill intervals were added.
AnotherRoundNeeded |= !LRE.empty();
// Spill VReg. If this introduces new intervals we'll need another round
// of allocation.
SmallVector<unsigned, 8> NewVRegs;
spillVReg(VReg, NewVRegs, MF, LIS, VRM, VRegSpiller);
AnotherRoundNeeded |= !NewVRegs.empty();
}
}
@ -683,7 +714,7 @@ bool RegAllocPBQP::runOnMachineFunction(MachineFunction &MF) {
DEBUG(dbgs() << " PBQP Regalloc round " << Round << ":\n");
PBQPRAGraph G(PBQPRAGraph::GraphMetadata(MF, LIS, MBFI));
initializeGraph(G);
initializeGraph(G, VRM, *VRegSpiller);
ConstraintsRoot->apply(G);
#ifndef NDEBUG