#define DEBUG_TYPE "regalloc"
#include "RegisterCoalescer.h"
#include "LiveDebugVariables.h"
-
-#include "llvm/Pass.h"
-#include "llvm/Value.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/RegisterClassInfo.h"
#include "llvm/CodeGen/VirtRegMap.h"
+#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetSubtargetInfo.h"
+#include "llvm/Value.h"
#include <algorithm>
#include <cmath>
using namespace llvm;
// Update LiveDebugVariables.
LDV->renameRegister(SrcReg, DstReg, SubIdx);
+ SmallPtrSet<MachineInstr*, 8> Visited;
for (MachineRegisterInfo::reg_iterator I = MRI->reg_begin(SrcReg);
MachineInstr *UseMI = I.skipInstruction();) {
+ // Each instruction can only be rewritten once because sub-register
+ // composition is not always idempotent. When SrcReg != DstReg, rewriting
+ // the UseMI operands removes them from the SrcReg use-def chain, but when
+ // SrcReg is DstReg we could encounter UseMI twice if it has multiple
+ // operands mentioning the virtual register.
+ if (SrcReg == DstReg && !Visited.insert(UseMI))
+ continue;
+
SmallVector<unsigned,8> Ops;
bool Reads, Writes;
tie(Reads, Writes) = UseMI->readsWritesVirtualRegister(SrcReg, &Ops);