Delete dead code after rematerializing.
LiveRangeEdit::eliminateDeadDefs() will eventually be used by coalescing,
splitting, and spilling for dead code elimination. It can delete chains of dead
instructions as long as there are no dependency loops.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127287 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveRangeEdit.cpp b/lib/CodeGen/LiveRangeEdit.cpp
index 7de1284..4e2c00d 100644
--- a/lib/CodeGen/LiveRangeEdit.cpp
+++ b/lib/CodeGen/LiveRangeEdit.cpp
@@ -13,9 +13,12 @@
#include "LiveRangeEdit.h"
#include "VirtRegMap.h"
+#include "llvm/ADT/SetVector.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
using namespace llvm;
@@ -128,3 +131,59 @@
return lis.InsertMachineInstrInMaps(--MI).getDefIndex();
}
+void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
+ LiveIntervals &LIS,
+ const TargetInstrInfo &TII) {
+ SetVector<LiveInterval*,
+ SmallVector<LiveInterval*, 8>,
+ SmallPtrSet<LiveInterval*, 8> > ToShrink;
+
+ for (;;) {
+ // Erase all dead defs.
+ while (!Dead.empty()) {
+ MachineInstr *MI = Dead.pop_back_val();
+ assert(MI->allDefsAreDead() && "Def isn't really dead");
+
+ // Never delete inline asm.
+ if (MI->isInlineAsm())
+ continue;
+
+ // Use the same criteria as DeadMachineInstructionElim.
+ bool SawStore = false;
+ if (!MI->isSafeToMove(&TII, 0, SawStore))
+ continue;
+
+ SlotIndex Idx = LIS.getInstructionIndex(MI).getDefIndex();
+ DEBUG(dbgs() << "Deleting dead def " << Idx << '\t' << *MI);
+
+ // Check for live intervals that may shrink
+ for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
+ MOE = MI->operands_end(); MOI != MOE; ++MOI) {
+ if (!MOI->isReg())
+ continue;
+ unsigned Reg = MOI->getReg();
+ if (!TargetRegisterInfo::isVirtualRegister(Reg))
+ continue;
+ LiveInterval &LI = LIS.getInterval(Reg);
+ // Remove defined value.
+ if (MOI->isDef())
+ if (VNInfo *VNI = LI.getVNInfoAt(Idx))
+ LI.removeValNo(VNI);
+ // Shrink read registers.
+ if (MI->readsVirtualRegister(Reg))
+ ToShrink.insert(&LI);
+ }
+
+ LIS.RemoveMachineInstrFromMaps(MI);
+ MI->eraseFromParent();
+ }
+
+ if (ToShrink.empty())
+ break;
+
+ // Shrink just one live interval. Then delete new dead defs.
+ LIS.shrinkToUses(ToShrink.back(), &Dead);
+ ToShrink.pop_back();
+ }
+}
+