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-rw-r--r--lib/CodeGen/InlineSpiller.cpp321
1 files changed, 239 insertions, 82 deletions
diff --git a/lib/CodeGen/InlineSpiller.cpp b/lib/CodeGen/InlineSpiller.cpp
index f0f69872b0..c1168c92bc 100644
--- a/lib/CodeGen/InlineSpiller.cpp
+++ b/lib/CodeGen/InlineSpiller.cpp
@@ -17,6 +17,7 @@
#include "LiveRangeEdit.h"
#include "VirtRegMap.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/TinyPtrVector.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/LiveStackAnalysis.h"
@@ -75,30 +76,55 @@ class InlineSpiller : public Spiller {
// Values that failed to remat at some point.
SmallPtrSet<VNInfo*, 8> UsedValues;
+public:
// Information about a value that was defined by a copy from a sibling
// register.
struct SibValueInfo {
// True when all reaching defs were reloads: No spill is necessary.
bool AllDefsAreReloads;
+ // True when value is defined by an original PHI not from splitting.
+ bool DefByOrigPHI;
+
// The preferred register to spill.
unsigned SpillReg;
// The value of SpillReg that should be spilled.
VNInfo *SpillVNI;
+ // The block where SpillVNI should be spilled. Currently, this must be the
+ // block containing SpillVNI->def.
+ MachineBasicBlock *SpillMBB;
+
// A defining instruction that is not a sibling copy or a reload, or NULL.
// This can be used as a template for rematerialization.
MachineInstr *DefMI;
+ // List of values that depend on this one. These values are actually the
+ // same, but live range splitting has placed them in different registers,
+ // or SSA update needed to insert PHI-defs to preserve SSA form. This is
+ // copies of the current value and phi-kills. Usually only phi-kills cause
+ // more than one dependent value.
+ TinyPtrVector<VNInfo*> Deps;
+
SibValueInfo(unsigned Reg, VNInfo *VNI)
- : AllDefsAreReloads(false), SpillReg(Reg), SpillVNI(VNI), DefMI(0) {}
+ : AllDefsAreReloads(true), DefByOrigPHI(false),
+ SpillReg(Reg), SpillVNI(VNI), SpillMBB(0), DefMI(0) {}
+
+ // Returns true when a def has been found.
+ bool hasDef() const { return DefByOrigPHI || DefMI; }
};
+private:
// Values in RegsToSpill defined by sibling copies.
typedef DenseMap<VNInfo*, SibValueInfo> SibValueMap;
SibValueMap SibValues;
+ // Values live-out from basic blocks. This is the same as
+ // LI.getVNInfoAt(LIS.getMBBEndIdx(MBB).getPrevSlot())
+ typedef DenseMap<MachineBasicBlock*, VNInfo*> LiveOutMap;
+ LiveOutMap LiveOutValues;
+
// Dead defs generated during spilling.
SmallVector<MachineInstr*, 8> DeadDefs;
@@ -134,6 +160,7 @@ private:
bool isSibling(unsigned Reg);
MachineInstr *traceSiblingValue(unsigned, VNInfo*, VNInfo*);
+ void propagateSiblingValue(SibValueMap::iterator, VNInfo *VNI = 0);
void analyzeSiblingValues();
bool hoistSpill(LiveInterval &SpillLI, MachineInstr *CopyMI);
@@ -282,6 +309,153 @@ bool InlineSpiller::isSibling(unsigned Reg) {
VRM.getOriginal(Reg) == Original;
}
+#ifndef NDEBUG
+static raw_ostream &operator<<(raw_ostream &OS,
+ const InlineSpiller::SibValueInfo &SVI) {
+ OS << "spill " << PrintReg(SVI.SpillReg) << ':'
+ << SVI.SpillVNI->id << '@' << SVI.SpillVNI->def;
+ if (SVI.SpillMBB)
+ OS << " in BB#" << SVI.SpillMBB->getNumber();
+ if (SVI.AllDefsAreReloads)
+ OS << " all-reloads";
+ if (SVI.DefByOrigPHI)
+ OS << " orig-phi";
+ OS << " deps[";
+ for (unsigned i = 0, e = SVI.Deps.size(); i != e; ++i)
+ OS << ' ' << SVI.Deps[i]->id << '@' << SVI.Deps[i]->def;
+ OS << " ]";
+ if (SVI.DefMI)
+ OS << " def: " << *SVI.DefMI;
+ else
+ OS << '\n';
+ return OS;
+}
+#endif
+
+/// propagateSiblingValue - Propagate the value in SVI to dependents if it is
+/// known. Otherwise remember the dependency for later.
+///
+/// @param SVI SibValues entry to propagate.
+/// @param VNI Dependent value, or NULL to propagate to all saved dependents.
+void InlineSpiller::propagateSiblingValue(SibValueMap::iterator SVI,
+ VNInfo *VNI) {
+ // When VNI is non-NULL, add it to SVI's deps, and only propagate to that.
+ TinyPtrVector<VNInfo*> FirstDeps;
+ if (VNI) {
+ FirstDeps.push_back(VNI);
+ SVI->second.Deps.push_back(VNI);
+ }
+
+ // Has the value been completely determined yet? If not, defer propagation.
+ if (!SVI->second.hasDef())
+ return;
+
+ // Work list of values to propagate. It would be nice to use a SetVector
+ // here, but then we would be forced to use a SmallSet.
+ SmallVector<SibValueMap::iterator, 8> WorkList(1, SVI);
+ SmallPtrSet<VNInfo*, 8> WorkSet;
+
+ do {
+ SVI = WorkList.pop_back_val();
+ WorkSet.erase(SVI->first);
+ TinyPtrVector<VNInfo*> *Deps = VNI ? &FirstDeps : &SVI->second.Deps;
+ VNI = 0;
+
+ SibValueInfo &SV = SVI->second;
+ if (!SV.SpillMBB)
+ SV.SpillMBB = LIS.getMBBFromIndex(SV.SpillVNI->def);
+
+ DEBUG(dbgs() << " prop to " << Deps->size() << ": "
+ << SVI->first->id << '@' << SVI->first->def << ":\t" << SV);
+
+ assert(SV.hasDef() && "Propagating undefined value");
+
+ // Should this value be propagated as a preferred spill candidate? We don't
+ // propagate values of registers that are about to spill.
+ bool PropSpill = !isRegToSpill(SV.SpillReg);
+ unsigned SpillDepth = ~0u;
+
+ for (TinyPtrVector<VNInfo*>::iterator DepI = Deps->begin(),
+ DepE = Deps->end(); DepI != DepE; ++DepI) {
+ SibValueMap::iterator DepSVI = SibValues.find(*DepI);
+ assert(DepSVI != SibValues.end() && "Dependent value not in SibValues");
+ SibValueInfo &DepSV = DepSVI->second;
+ if (!DepSV.SpillMBB)
+ DepSV.SpillMBB = LIS.getMBBFromIndex(DepSV.SpillVNI->def);
+
+ bool Changed = false;
+
+ // Propagate defining instruction.
+ if (!DepSV.hasDef()) {
+ Changed = true;
+ DepSV.DefMI = SV.DefMI;
+ DepSV.DefByOrigPHI = SV.DefByOrigPHI;
+ }
+
+ // Propagate AllDefsAreReloads. For PHI values, this computes an AND of
+ // all predecessors.
+ if (!SV.AllDefsAreReloads && DepSV.AllDefsAreReloads) {
+ Changed = true;
+ DepSV.AllDefsAreReloads = false;
+ }
+
+ // Propagate best spill value.
+ if (PropSpill && SV.SpillVNI != DepSV.SpillVNI) {
+ if (SV.SpillMBB == DepSV.SpillMBB) {
+ // DepSV is in the same block. Hoist when dominated.
+ if (SV.SpillVNI->def < DepSV.SpillVNI->def) {
+ // This is an alternative def earlier in the same MBB.
+ // Hoist the spill as far as possible in SpillMBB. This can ease
+ // register pressure:
+ //
+ // x = def
+ // y = use x
+ // s = copy x
+ //
+ // Hoisting the spill of s to immediately after the def removes the
+ // interference between x and y:
+ //
+ // x = def
+ // spill x
+ // y = use x<kill>
+ //
+ Changed = true;
+ DepSV.SpillReg = SV.SpillReg;
+ DepSV.SpillVNI = SV.SpillVNI;
+ DepSV.SpillMBB = SV.SpillMBB;
+ }
+ } else {
+ // DepSV is in a different block.
+ if (SpillDepth == ~0u)
+ SpillDepth = Loops.getLoopDepth(SV.SpillMBB);
+
+ // Also hoist spills to blocks with smaller loop depth, but make sure
+ // that the new value dominates. Non-phi dependents are always
+ // dominated, phis need checking.
+ if ((Loops.getLoopDepth(DepSV.SpillMBB) > SpillDepth) &&
+ (!DepSVI->first->isPHIDef() ||
+ MDT.dominates(SV.SpillMBB, DepSV.SpillMBB))) {
+ Changed = true;
+ DepSV.SpillReg = SV.SpillReg;
+ DepSV.SpillVNI = SV.SpillVNI;
+ DepSV.SpillMBB = SV.SpillMBB;
+ }
+ }
+ }
+
+ if (!Changed)
+ continue;
+
+ // Something changed in DepSVI. Propagate to dependents.
+ if (WorkSet.insert(DepSVI->first))
+ WorkList.push_back(DepSVI);
+
+ DEBUG(dbgs() << " update " << DepSVI->first->id << '@'
+ << DepSVI->first->def << " to:\t" << DepSV);
+ }
+ } while (!WorkList.empty());
+}
+
/// traceSiblingValue - Trace a value that is about to be spilled back to the
/// real defining instructions by looking through sibling copies. Always stay
/// within the range of OrigVNI so the registers are known to carry the same
@@ -294,84 +468,68 @@ bool InlineSpiller::isSibling(unsigned Reg) {
///
MachineInstr *InlineSpiller::traceSiblingValue(unsigned UseReg, VNInfo *UseVNI,
VNInfo *OrigVNI) {
+ // Check if a cached value already exists.
+ SibValueMap::iterator SVI;
+ bool Inserted;
+ tie(SVI, Inserted) =
+ SibValues.insert(std::make_pair(UseVNI, SibValueInfo(UseReg, UseVNI)));
+ if (!Inserted) {
+ DEBUG(dbgs() << "Cached value " << PrintReg(UseReg) << ':'
+ << UseVNI->id << '@' << UseVNI->def << ' ' << SVI->second);
+ return SVI->second.DefMI;
+ }
+
DEBUG(dbgs() << "Tracing value " << PrintReg(UseReg) << ':'
<< UseVNI->id << '@' << UseVNI->def << '\n');
- SmallPtrSet<VNInfo*, 8> Visited;
+
+ // List of (Reg, VNI) that have been inserted into SibValues, but need to be
+ // processed.
SmallVector<std::pair<unsigned, VNInfo*>, 8> WorkList;
WorkList.push_back(std::make_pair(UseReg, UseVNI));
- // Best spill candidate seen so far. This must dominate UseVNI.
- SibValueInfo SVI(UseReg, UseVNI);
- MachineBasicBlock *UseMBB = LIS.getMBBFromIndex(UseVNI->def);
- MachineBasicBlock *SpillMBB = UseMBB;
- unsigned SpillDepth = Loops.getLoopDepth(SpillMBB);
- bool SeenOrigPHI = false; // Original PHI met.
-
do {
unsigned Reg;
VNInfo *VNI;
tie(Reg, VNI) = WorkList.pop_back_val();
- if (!Visited.insert(VNI))
- continue;
+ DEBUG(dbgs() << " " << PrintReg(Reg) << ':' << VNI->id << '@' << VNI->def
+ << ":\t");
- // Is this value a better spill candidate?
- if (!isRegToSpill(Reg)) {
- MachineBasicBlock *MBB = LIS.getMBBFromIndex(VNI->def);
- if (MBB == SpillMBB) {
- // This is an alternative def earlier in the same MBB.
- // Hoist the spill as far as possible in SpillMBB. This can ease
- // register pressure:
- //
- // x = def
- // y = use x
- // s = copy x
- //
- // Hoisting the spill of s to immediately after the def removes the
- // interference between x and y:
- //
- // x = def
- // spill x
- // y = use x<kill>
- //
- if (VNI->def < SVI.SpillVNI->def) {
- DEBUG(dbgs() << " hoist in BB#" << MBB->getNumber() << ": "
- << PrintReg(Reg) << ':' << VNI->id << '@' << VNI->def
- << '\n');
- SVI.SpillReg = Reg;
- SVI.SpillVNI = VNI;
- }
- } else if (MBB != UseMBB && MDT.dominates(MBB, UseMBB)) {
- // This is a valid spill location dominating UseVNI.
- // Prefer to spill at a smaller loop depth.
- unsigned Depth = Loops.getLoopDepth(MBB);
- if (Depth < SpillDepth) {
- DEBUG(dbgs() << " spill depth " << Depth << ": " << PrintReg(Reg)
- << ':' << VNI->id << '@' << VNI->def << '\n');
- SVI.SpillReg = Reg;
- SVI.SpillVNI = VNI;
- SpillMBB = MBB;
- SpillDepth = Depth;
- }
- }
- }
+ // First check if this value has already been computed.
+ SVI = SibValues.find(VNI);
+ assert(SVI != SibValues.end() && "Missing SibValues entry");
// Trace through PHI-defs created by live range splitting.
if (VNI->isPHIDef()) {
if (VNI->def == OrigVNI->def) {
- DEBUG(dbgs() << " orig phi value " << PrintReg(Reg) << ':'
- << VNI->id << '@' << VNI->def << '\n');
- SeenOrigPHI = true;
+ DEBUG(dbgs() << "orig phi value\n");
+ SVI->second.DefByOrigPHI = true;
+ SVI->second.AllDefsAreReloads = false;
+ propagateSiblingValue(SVI);
continue;
}
// Get values live-out of predecessors.
LiveInterval &LI = LIS.getInterval(Reg);
MachineBasicBlock *MBB = LIS.getMBBFromIndex(VNI->def);
+ DEBUG(dbgs() << "split phi value, check " << MBB->pred_size()
+ << " preds\n");
for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
- VNInfo *PVNI = LI.getVNInfoAt(LIS.getMBBEndIdx(*PI).getPrevSlot());
- if (PVNI)
+ // Use a cache of block live-out values. This is faster than using
+ // getVNInfoAt on complex intervals.
+ VNInfo *&PVNI = LiveOutValues[*PI];
+ if (!PVNI)
+ PVNI = LI.getVNInfoAt(LIS.getMBBEndIdx(*PI).getPrevSlot());
+ if (!PVNI)
+ continue;
+ // Known predecessor value? Try an insertion.
+ tie(SVI, Inserted) =
+ SibValues.insert(std::make_pair(PVNI, SibValueInfo(Reg, PVNI)));
+ // This is the first time we see PVNI, add it to the worklist.
+ if (Inserted)
WorkList.push_back(std::make_pair(Reg, PVNI));
+ propagateSiblingValue(SVI, VNI);
}
+ // Next work list item.
continue;
}
@@ -384,46 +542,43 @@ MachineInstr *InlineSpiller::traceSiblingValue(unsigned UseReg, VNInfo *UseVNI,
LiveInterval &SrcLI = LIS.getInterval(SrcReg);
VNInfo *SrcVNI = SrcLI.getVNInfoAt(VNI->def.getUseIndex());
assert(SrcVNI && "Copy from non-existing value");
- DEBUG(dbgs() << " copy of " << PrintReg(SrcReg) << ':'
+ DEBUG(dbgs() << "copy of " << PrintReg(SrcReg) << ':'
<< SrcVNI->id << '@' << SrcVNI->def << '\n');
- WorkList.push_back(std::make_pair(SrcReg, SrcVNI));
+ // Known sibling source value? Try an insertion.
+ tie(SVI, Inserted) = SibValues.insert(std::make_pair(SrcVNI,
+ SibValueInfo(SrcReg, SrcVNI)));
+ // This is the first time we see Src, add it to the worklist.
+ if (Inserted)
+ WorkList.push_back(std::make_pair(SrcReg, SrcVNI));
+ propagateSiblingValue(SVI, VNI);
+ // Next work list item.
continue;
}
}
// Track reachable reloads.
+ SVI->second.DefMI = MI;
+ SVI->second.SpillMBB = MI->getParent();
int FI;
if (Reg == TII.isLoadFromStackSlot(MI, FI) && FI == StackSlot) {
- DEBUG(dbgs() << " reload " << PrintReg(Reg) << ':'
- << VNI->id << "@" << VNI->def << '\n');
- SVI.AllDefsAreReloads = true;
+ DEBUG(dbgs() << "reload\n");
+ propagateSiblingValue(SVI);
+ // Next work list item.
continue;
}
- // We have an 'original' def. Don't record trivial cases.
- if (VNI == UseVNI) {
- DEBUG(dbgs() << "Not a sibling copy.\n");
- return MI;
- }
-
// Potential remat candidate.
- DEBUG(dbgs() << " def " << PrintReg(Reg) << ':'
- << VNI->id << '@' << VNI->def << '\t' << *MI);
- SVI.DefMI = MI;
+ DEBUG(dbgs() << "def " << *MI);
+ SVI->second.AllDefsAreReloads = false;
+ propagateSiblingValue(SVI);
} while (!WorkList.empty());
- if (SeenOrigPHI || SVI.DefMI)
- SVI.AllDefsAreReloads = false;
-
- DEBUG({
- if (SVI.AllDefsAreReloads)
- dbgs() << "All defs are reloads.\n";
- else
- dbgs() << "Prefer to spill " << PrintReg(SVI.SpillReg) << ':'
- << SVI.SpillVNI->id << '@' << SVI.SpillVNI->def << '\n';
- });
- SibValues.insert(std::make_pair(UseVNI, SVI));
- return SVI.DefMI;
+ // Look up the value we were looking for. We already did this lokup at the
+ // top of the function, but SibValues may have been invalidated.
+ SVI = SibValues.find(UseVNI);
+ assert(SVI != SibValues.end() && "Didn't compute requested info");
+ DEBUG(dbgs() << " traced to:\t" << SVI->second);
+ return SVI->second.DefMI;
}
/// analyzeSiblingValues - Trace values defined by sibling copies back to
@@ -432,6 +587,7 @@ MachineInstr *InlineSpiller::traceSiblingValue(unsigned UseReg, VNInfo *UseVNI,
/// Keep track of values that may be rematerializable.
void InlineSpiller::analyzeSiblingValues() {
SibValues.clear();
+ LiveOutValues.clear();
// No siblings at all?
if (Edit->getReg() == Original)
@@ -506,6 +662,7 @@ bool InlineSpiller::hoistSpill(LiveInterval &SpillLI, MachineInstr *CopyMI) {
// Already spilled everywhere.
if (SVI.AllDefsAreReloads) {
+ DEBUG(dbgs() << "\tno spill needed: " << SVI);
++NumOmitReloadSpill;
return true;
}
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