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MachineBasicBlock: Cleanup computeRegisterLiveness()

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- Clean documentation comment
- Change the API to accept an iterator so you can actually pass
  MachineBasicBlock::end() now.
- Add more "const".

llvm-svn: 238288
This commit is contained in:
Matthias Braun 2015-05-27 05:12:39 +00:00
parent 3c24983b23
commit d199caeaa9
2 changed files with 23 additions and 24 deletions
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17
include/llvm/CodeGen/MachineBasicBlock.h
View File

@ -633,17 +633,18 @@ public:
///< neighborhood.
};
/// computeRegisterLiveness - Return whether (physical) register \c Reg
/// has been <def>ined and not <kill>ed as of just before \c MI.
/// Return whether (physical) register \p Reg has been <def>ined and not
/// <kill>ed as of just before \p Before.
///
/// Search is localised to a neighborhood of
/// \c Neighborhood instructions before (searching for defs or kills) and
/// Neighborhood instructions after (searching just for defs) MI.
/// Search is localised to a neighborhood of \p Neighborhood instructions
/// before (searching for defs or kills) and \p Neighborhood instructions
/// after (searching just for defs) \p Before.
///
/// \c Reg must be a physical register.
/// \p Reg must be a physical register.
LivenessQueryResult computeRegisterLiveness(const TargetRegisterInfo *TRI,
unsigned Reg, MachineInstr *MI,
unsigned Neighborhood=10);
unsigned Reg,
const_iterator Before,
unsigned Neighborhood=10) const;
// Debugging methods.
void dump() const;

30
lib/CodeGen/MachineBasicBlock.cpp
View File

@ -1129,21 +1129,19 @@ getWeightIterator(MachineBasicBlock::const_succ_iterator I) const {
/// instructions after (searching just for defs) MI.
MachineBasicBlock::LivenessQueryResult
MachineBasicBlock::computeRegisterLiveness(const TargetRegisterInfo *TRI,
unsigned Reg, MachineInstr *MI,
unsigned Neighborhood) {
unsigned Reg, const_iterator Before,
unsigned Neighborhood) const {
unsigned N = Neighborhood;
MachineBasicBlock *MBB = MI->getParent();
// Start by searching backwards from MI, looking for kills, reads or defs.
MachineBasicBlock::iterator I(MI);
// Start by searching backwards from Before, looking for kills, reads or defs.
const_iterator I(Before);
// If this is the first insn in the block, don't search backwards.
if (I != MBB->begin()) {
if (I != begin()) {
do {
--I;
MachineOperandIteratorBase::PhysRegInfo Analysis =
MIOperands(I).analyzePhysReg(Reg, TRI);
ConstMIOperands(I).analyzePhysReg(Reg, TRI);
if (Analysis.Defines)
// Outputs happen after inputs so they take precedence if both are
@ -1158,15 +1156,15 @@ MachineBasicBlock::computeRegisterLiveness(const TargetRegisterInfo *TRI,
// Defined or read without a previous kill - live.
return Analysis.Reads ? LQR_Live : LQR_OverlappingLive;
} while (I != MBB->begin() && --N > 0);
} while (I != begin() && --N > 0);
}
// Did we get to the start of the block?
if (I == MBB->begin()) {
if (I == begin()) {
// If so, the register's state is definitely defined by the live-in state.
for (MCRegAliasIterator RAI(Reg, TRI, /*IncludeSelf=*/true);
RAI.isValid(); ++RAI) {
if (MBB->isLiveIn(*RAI))
if (isLiveIn(*RAI))
return (*RAI == Reg) ? LQR_Live : LQR_OverlappingLive;
}
@ -1175,13 +1173,13 @@ MachineBasicBlock::computeRegisterLiveness(const TargetRegisterInfo *TRI,
N = Neighborhood;
// Try searching forwards from MI, looking for reads or defs.
I = MachineBasicBlock::iterator(MI);
// Try searching forwards from Before, looking for reads or defs.
I = const_iterator(Before);
// If this is the last insn in the block, don't search forwards.
if (I != MBB->end()) {
for (++I; I != MBB->end() && N > 0; ++I, --N) {
if (I != end()) {
for (++I; I != end() && N > 0; ++I, --N) {
MachineOperandIteratorBase::PhysRegInfo Analysis =
MIOperands(I).analyzePhysReg(Reg, TRI);
ConstMIOperands(I).analyzePhysReg(Reg, TRI);
if (Analysis.ReadsOverlap)
// Used, therefore must have been live.