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Add MachineInstr::readsWritesVirtualRegister() to determine if an instruction

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reads or writes a register.

This takes partial redefines and undef uses into account.

Don't actually use it yet. That caused miscompiles.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@104372 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2010-05-21 20:02:01 +00:00
parent 379fe83dda
commit 18b2c9d3bf
2 changed files with 26 additions and 12 deletions
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12
include/llvm/CodeGen/MachineInstr.h
View File

@ -28,6 +28,7 @@
namespace llvm {
template <typename T> class SmallVectorImpl;
class AliasAnalysis;
class TargetInstrDesc;
class TargetInstrInfo;
@ -239,7 +240,16 @@ public:
/// readsVirtualRegister - Return true if the MachineInstr reads the specified
/// virtual register. Take into account that a partial define is a
/// read-modify-write operation.
bool readsVirtualRegister(unsigned Reg) const;
bool readsVirtualRegister(unsigned Reg) const {
return readsWritesVirtualRegister(Reg).first;
}
/// readsWritesVirtualRegister - Return a pair of bools (reads, writes)
/// indicating if this instruction reads or writes Reg. This also considers
/// partial defines.
/// If Ops is not null, all operand indices for Reg are added.
std::pair<bool,bool> readsWritesVirtualRegister(unsigned Reg,
SmallVectorImpl<unsigned> *Ops = 0) const;
/// killsRegister - Return true if the MachineInstr kills the specified
/// register. If TargetRegisterInfo is passed, then it also checks if there is

26
lib/CodeGen/MachineInstr.cpp
View File

@ -782,27 +782,31 @@ int MachineInstr::findRegisterUseOperandIdx(unsigned Reg, bool isKill,
return -1;
}
/// readsVirtualRegister - Return true if the MachineInstr reads the specified
/// virtual register. Take into account that a partial define is a
/// read-modify-write operation.
bool MachineInstr::readsVirtualRegister(unsigned Reg) const {
bool PartDef = false; // Partial redefine
bool FullDef = false; // Full define
/// readsWritesVirtualRegister - Return a pair of bools (reads, writes)
/// indicating if this instruction reads or writes Reg. This also considers
/// partial defines.
std::pair<bool,bool>
MachineInstr::readsWritesVirtualRegister(unsigned Reg,
SmallVectorImpl<unsigned> *Ops) const {
bool PartDef = false; // Partial redefine.
bool FullDef = false; // Full define.
bool Use = false;
for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
const MachineOperand &MO = getOperand(i);
if (!MO.isReg() || MO.getReg() != Reg)
continue;
if (Ops)
Ops->push_back(i);
if (MO.isUse())
return true;
if (MO.getSubReg())
Use |= !MO.isUndef();
else if (MO.getSubReg())
PartDef = true;
else
FullDef = true;
}
// A partial register definition causes a read unless the full register is
// also defined.
return PartDef && !FullDef;
// A partial redefine uses Reg unless there is also a full define.
return std::make_pair(Use || (PartDef && !FullDef), PartDef || FullDef);
}
/// findRegisterDefOperandIdx() - Returns the operand index that is a def of