[llvm] r255192 - RegisterPressure: Factor out liveness dead-def detection logic; NFCI
Matthias Braun via llvm-commits
llvm-commits at lists.llvm.org
Wed Dec 9 17:04:15 PST 2015
Author: matze
Date: Wed Dec 9 19:04:15 2015
New Revision: 255192
URL: http://llvm.org/viewvc/llvm-project?rev=255192&view=rev
Log:
RegisterPressure: Factor out liveness dead-def detection logic; NFCI
Detecting additional dead-defs without a dead flag that are only visible
through liveness information should be part of the register operand
collection not intertwined with the register pressure update logic.
Modified:
llvm/trunk/include/llvm/CodeGen/RegisterPressure.h
llvm/trunk/lib/CodeGen/RegisterPressure.cpp
Modified: llvm/trunk/include/llvm/CodeGen/RegisterPressure.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/RegisterPressure.h?rev=255192&r1=255191&r2=255192&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/RegisterPressure.h (original)
+++ llvm/trunk/include/llvm/CodeGen/RegisterPressure.h Wed Dec 9 19:04:15 2015
@@ -441,8 +441,6 @@ protected:
/// after the current position.
SlotIndex getCurrSlot() const;
- const LiveRange *getLiveRange(unsigned Reg) const;
-
void increaseRegPressure(ArrayRef<unsigned> Regs);
void decreaseRegPressure(ArrayRef<unsigned> Regs);
Modified: llvm/trunk/lib/CodeGen/RegisterPressure.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/RegisterPressure.cpp?rev=255192&r1=255191&r2=255192&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/RegisterPressure.cpp (original)
+++ llvm/trunk/lib/CodeGen/RegisterPressure.cpp Wed Dec 9 19:04:15 2015
@@ -171,10 +171,10 @@ void LiveRegSet::clear() {
Regs.clear();
}
-const LiveRange *RegPressureTracker::getLiveRange(unsigned Reg) const {
+static const LiveRange *getLiveRange(const LiveIntervals &LIS, unsigned Reg) {
if (TargetRegisterInfo::isVirtualRegister(Reg))
- return &LIS->getInterval(Reg);
- return LIS->getCachedRegUnit(Reg);
+ return &LIS.getInterval(Reg);
+ return LIS.getCachedRegUnit(Reg);
}
void RegPressureTracker::reset() {
@@ -323,6 +323,10 @@ public:
void collect(const MachineInstr &MI, const TargetRegisterInfo &TRI,
const MachineRegisterInfo &MRI, bool IgnoreDead = false);
+
+ /// Use liveness information to find dead defs not marked with a dead flag
+ /// and move them to the DeadDefs vector.
+ void detectDeadDefs(const MachineInstr &MI, const LiveIntervals &LIS);
};
/// Collect this instruction's unique uses and defs into SmallVectors for
@@ -393,6 +397,27 @@ void RegisterOperands::collect(const Mac
Collector.collectInstr(MI);
}
+void RegisterOperands::detectDeadDefs(const MachineInstr &MI,
+ const LiveIntervals &LIS) {
+ SlotIndex SlotIdx = LIS.getInstructionIndex(&MI);
+ for (SmallVectorImpl<unsigned>::iterator RI = Defs.begin();
+ RI != Defs.end(); /*empty*/) {
+ unsigned Reg = *RI;
+ const LiveRange *LR = getLiveRange(LIS, Reg);
+ if (LR != nullptr) {
+ LiveQueryResult LRQ = LR->Query(SlotIdx);
+ if (LRQ.isDeadDef()) {
+ // LiveIntervals knows this is a dead even though it's MachineOperand is
+ // not flagged as such.
+ DeadDefs.push_back(Reg);
+ RI = Defs.erase(RI);
+ continue;
+ }
+ }
+ ++RI;
+ }
+}
+
} // namespace
/// Initialize an array of N PressureDiffs.
@@ -514,8 +539,11 @@ void RegPressureTracker::recede(SmallVec
if (RequireIntervals && isTopClosed())
static_cast<IntervalPressure&>(P).openTop(SlotIdx);
+ const MachineInstr &MI = *CurrPos;
RegisterOperands RegOpers;
- RegOpers.collect(*CurrPos, *TRI, *MRI);
+ RegOpers.collect(MI, *TRI, *MRI);
+ if (RequireIntervals)
+ RegOpers.detectDeadDefs(MI, *LIS);
if (PDiff)
collectPDiff(*PDiff, RegOpers, MRI);
@@ -527,26 +555,10 @@ void RegPressureTracker::recede(SmallVec
// Kill liveness at live defs.
// TODO: consider earlyclobbers?
for (unsigned Reg : RegOpers.Defs) {
- bool DeadDef = false;
- if (RequireIntervals) {
- const LiveRange *LR = getLiveRange(Reg);
- if (LR) {
- LiveQueryResult LRQ = LR->Query(SlotIdx);
- DeadDef = LRQ.isDeadDef();
- }
- }
- if (DeadDef) {
- // LiveIntervals knows this is a dead even though it's MachineOperand is
- // not flagged as such. Since this register will not be recorded as
- // live-out, increase its PDiff value to avoid underflowing pressure.
- if (PDiff)
- PDiff->addPressureChange(Reg, false, MRI);
- } else {
- if (LiveRegs.erase(Reg))
- decreaseRegPressure(Reg);
- else
- discoverLiveOut(Reg);
- }
+ if (LiveRegs.erase(Reg))
+ decreaseRegPressure(Reg);
+ else
+ discoverLiveOut(Reg);
}
// Generate liveness for uses.
@@ -554,7 +566,7 @@ void RegPressureTracker::recede(SmallVec
if (!LiveRegs.contains(Reg)) {
// Adjust liveouts if LiveIntervals are available.
if (RequireIntervals) {
- const LiveRange *LR = getLiveRange(Reg);
+ const LiveRange *LR = getLiveRange(*LIS, Reg);
if (LR) {
LiveQueryResult LRQ = LR->Query(SlotIdx);
if (!LRQ.isKill() && !LRQ.valueDefined())
@@ -606,7 +618,7 @@ void RegPressureTracker::advance() {
// Kill liveness at last uses.
bool lastUse = false;
if (RequireIntervals) {
- const LiveRange *LR = getLiveRange(Reg);
+ const LiveRange *LR = getLiveRange(*LIS, Reg);
lastUse = LR && LR->Query(SlotIdx).isKill();
} else {
// Allocatable physregs are always single-use before register rewriting.
@@ -726,22 +738,13 @@ void RegPressureTracker::bumpUpwardPress
RegisterOperands RegOpers;
RegOpers.collect(*MI, *TRI, *MRI, /*IgnoreDead=*/true);
assert(RegOpers.DeadDefs.size() == 0);
+ if (RequireIntervals)
+ RegOpers.detectDeadDefs(*MI, *LIS);
// Kill liveness at live defs.
for (unsigned Reg : RegOpers.Defs) {
- bool DeadDef = false;
- if (RequireIntervals) {
- const LiveRange *LR = getLiveRange(Reg);
- if (LR) {
- SlotIndex SlotIdx = LIS->getInstructionIndex(MI);
- LiveQueryResult LRQ = LR->Query(SlotIdx);
- DeadDef = LRQ.isDeadDef();
- }
- }
- if (!DeadDef) {
- if (!containsReg(RegOpers.Uses, Reg))
- decreaseRegPressure(Reg);
- }
+ if (!containsReg(RegOpers.Uses, Reg))
+ decreaseRegPressure(Reg);
}
// Generate liveness for uses.
for (unsigned Reg : RegOpers.Uses) {
@@ -926,7 +929,7 @@ void RegPressureTracker::bumpDownwardPre
// FIXME: allow the caller to pass in the list of vreg uses that remain
// to be bottom-scheduled to avoid searching uses at each query.
SlotIndex CurrIdx = getCurrSlot();
- const LiveRange *LR = getLiveRange(Reg);
+ const LiveRange *LR = getLiveRange(*LIS, Reg);
if (LR) {
LiveQueryResult LRQ = LR->Query(SlotIdx);
if (LRQ.isKill() && !findUseBetween(Reg, CurrIdx, SlotIdx, *MRI, LIS))
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