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-rw-r--r--llvm/include/llvm/Target/TargetInstrInfo.h8
-rw-r--r--llvm/lib/CodeGen/MachineCSE.cpp5
-rw-r--r--llvm/lib/Target/R600/SIInstrInfo.h2
3 files changed, 13 insertions, 2 deletions
diff --git a/llvm/include/llvm/Target/TargetInstrInfo.h b/llvm/include/llvm/Target/TargetInstrInfo.h
index f9c1e523e5a..2b0a888fa77 100644
--- a/llvm/include/llvm/Target/TargetInstrInfo.h
+++ b/llvm/include/llvm/Target/TargetInstrInfo.h
@@ -1235,6 +1235,14 @@ public:
return false;
}
+ /// \brief Return the value to use for the MachineCSE's LookAheadLimit,
+ /// which is a heuristic used for CSE'ing phys reg defs.
+ virtual unsigned getMachineCSELookAheadLimit () const {
+ // The default lookahead is small to prevent unprofitable quadratic
+ // behavior.
+ return 5;
+ }
+
private:
int CallFrameSetupOpcode, CallFrameDestroyOpcode;
};
diff --git a/llvm/lib/CodeGen/MachineCSE.cpp b/llvm/lib/CodeGen/MachineCSE.cpp
index f72d72a2e87..87aaaa0834c 100644
--- a/llvm/lib/CodeGen/MachineCSE.cpp
+++ b/llvm/lib/CodeGen/MachineCSE.cpp
@@ -48,7 +48,7 @@ namespace {
MachineRegisterInfo *MRI;
public:
static char ID; // Pass identification
- MachineCSE() : MachineFunctionPass(ID), LookAheadLimit(5), CurrVN(0) {
+ MachineCSE() : MachineFunctionPass(ID), LookAheadLimit(0), CurrVN(0) {
initializeMachineCSEPass(*PassRegistry::getPassRegistry());
}
@@ -69,7 +69,7 @@ namespace {
}
private:
- const unsigned LookAheadLimit;
+ unsigned LookAheadLimit;
typedef RecyclingAllocator<BumpPtrAllocator,
ScopedHashTableVal<MachineInstr*, unsigned> > AllocatorTy;
typedef ScopedHashTable<MachineInstr*, unsigned,
@@ -716,5 +716,6 @@ bool MachineCSE::runOnMachineFunction(MachineFunction &MF) {
MRI = &MF.getRegInfo();
AA = &getAnalysis<AliasAnalysis>();
DT = &getAnalysis<MachineDominatorTree>();
+ LookAheadLimit = TII->getMachineCSELookAheadLimit();
return PerformCSE(DT->getRootNode());
}
diff --git a/llvm/lib/Target/R600/SIInstrInfo.h b/llvm/lib/Target/R600/SIInstrInfo.h
index 7e049dca7b1..f952c0f0853 100644
--- a/llvm/lib/Target/R600/SIInstrInfo.h
+++ b/llvm/lib/Target/R600/SIInstrInfo.h
@@ -142,6 +142,8 @@ public:
bool FoldImmediate(MachineInstr *UseMI, MachineInstr *DefMI,
unsigned Reg, MachineRegisterInfo *MRI) const final;
+ unsigned getMachineCSELookAheadLimit() const override { return 500; }
+
bool isSALU(uint16_t Opcode) const {
return get(Opcode).TSFlags & SIInstrFlags::SALU;
}
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