[llvm-commits] [llvm] r139259 - /llvm/trunk/lib/CodeGen/InlineSpiller.cpp
Jakob Stoklund Olesen
stoklund at 2pi.dk
Wed Sep 7 14:43:53 PDT 2011
Author: stoklund
Date: Wed Sep 7 16:43:52 2011
New Revision: 139259
URL: http://llvm.org/viewvc/llvm-project?rev=139259&view=rev
Log:
Revert r139247 "Cache intermediate results during traceSiblingValue."
It broke the self host and clang-x86_64-darwin10-RA.
Modified:
llvm/trunk/lib/CodeGen/InlineSpiller.cpp
Modified: llvm/trunk/lib/CodeGen/InlineSpiller.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/InlineSpiller.cpp?rev=139259&r1=139258&r2=139259&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/InlineSpiller.cpp (original)
+++ llvm/trunk/lib/CodeGen/InlineSpiller.cpp Wed Sep 7 16:43:52 2011
@@ -17,7 +17,6 @@
#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"
@@ -76,55 +75,30 @@
// 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(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; }
+ : AllDefsAreReloads(false), SpillReg(Reg), SpillVNI(VNI), DefMI(0) {}
};
-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;
@@ -160,7 +134,6 @@
bool isSibling(unsigned Reg);
MachineInstr *traceSiblingValue(unsigned, VNInfo*, VNInfo*);
- void propagateSiblingValue(SibValueMap::iterator, VNInfo *VNI = 0);
void analyzeSiblingValues();
bool hoistSpill(LiveInterval &SpillLI, MachineInstr *CopyMI);
@@ -309,135 +282,6 @@
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.AllDefsAreReloads)
- OS << " all-reloads";
- if (SVI.DefByOrigPHI)
- OS << " orig-phi";
- 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) {
- SibValueInfo &SV = SVI->second;
-
- if (!SV.SpillMBB)
- SV.SpillMBB = LIS.getMBBFromIndex(SV.SpillVNI->def);
-
- // 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;
-
- // Further values that need to be updated.
- SmallVector<VNInfo*, 8> WorkList;
-
- // Defer propagation if the value is not known yet.
- if (VNI) {
- SV.Deps.push_back(VNI);
- // Don't propagate to other dependents than VNI. SVI hasn't changed.
- WorkList.push_back(VNI);
- } else {
- // No VNI given, update all Deps.
- WorkList.append(SV.Deps.begin(), SV.Deps.end());
- }
-
- // Has the value been completely determined yet? If not, defer propagation.
- if (!SV.hasDef())
- return;
-
- while (!WorkList.empty()) {
- SibValueMap::iterator DepSVI = SibValues.find(WorkList.pop_back_val());
- assert(DepSVI != SibValues.end() && "Dependent value not in SibValues");
- SibValueInfo &DepSV = DepSVI->second;
- bool Changed = false;
-
- if (!DepSV.SpillMBB)
- DepSV.SpillMBB = LIS.getMBBFromIndex(DepSV.SpillVNI->def);
-
- // 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.
- WorkList.append(DepSV.Deps.begin(), DepSV.Deps.end());
-
- DEBUG(dbgs() << " update " << DepSVI->first->id << '@'
- << DepSVI->first->def << " to:\t" << DepSV);
- }
-}
-
/// 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
@@ -450,68 +294,84 @@
///
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');
-
- // List of (Reg, VNI) that have been inserted into SibValues, but need to be
- // processed.
+ SmallPtrSet<VNInfo*, 8> Visited;
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();
- DEBUG(dbgs() << " " << PrintReg(Reg) << ':' << VNI->id << '@' << VNI->def
- << ":\t");
+ if (!Visited.insert(VNI))
+ continue;
- // First check if this value has already been computed.
- SVI = SibValues.find(VNI);
- assert(SVI != SibValues.end() && "Missing SibValues entry");
+ // 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;
+ }
+ }
+ }
// Trace through PHI-defs created by live range splitting.
if (VNI->isPHIDef()) {
if (VNI->def == OrigVNI->def) {
- DEBUG(dbgs() << "orig phi value\n");
- SVI->second.DefByOrigPHI = true;
- SVI->second.AllDefsAreReloads = false;
- propagateSiblingValue(SVI);
+ DEBUG(dbgs() << " orig phi value " << PrintReg(Reg) << ':'
+ << VNI->id << '@' << VNI->def << '\n');
+ SeenOrigPHI = true;
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) {
- // 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)
+ VNInfo *PVNI = LI.getVNInfoAt(LIS.getMBBEndIdx(*PI).getPrevSlot());
+ if (PVNI)
WorkList.push_back(std::make_pair(Reg, PVNI));
- propagateSiblingValue(SVI, VNI);
}
- // Next work list item.
continue;
}
@@ -524,43 +384,46 @@
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');
- // 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.
+ WorkList.push_back(std::make_pair(SrcReg, SrcVNI));
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\n");
- propagateSiblingValue(SVI);
- // Next work list item.
+ DEBUG(dbgs() << " reload " << PrintReg(Reg) << ':'
+ << VNI->id << "@" << VNI->def << '\n');
+ SVI.AllDefsAreReloads = true;
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 " << *MI);
- SVI->second.AllDefsAreReloads = false;
- propagateSiblingValue(SVI);
+ DEBUG(dbgs() << " def " << PrintReg(Reg) << ':'
+ << VNI->id << '@' << VNI->def << '\t' << *MI);
+ SVI.DefMI = MI;
} while (!WorkList.empty());
- // 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;
+ 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;
}
/// analyzeSiblingValues - Trace values defined by sibling copies back to
@@ -569,7 +432,6 @@
/// Keep track of values that may be rematerializable.
void InlineSpiller::analyzeSiblingValues() {
SibValues.clear();
- LiveOutValues.clear();
// No siblings at all?
if (Edit->getReg() == Original)
@@ -644,7 +506,6 @@
// Already spilled everywhere.
if (SVI.AllDefsAreReloads) {
- DEBUG(dbgs() << "\tno spill needed: " << SVI);
++NumOmitReloadSpill;
return true;
}
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