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[Hexagon] Generalize DAG mutation for function calls 

Add barrier edges to check for any physical register. The previous code
worked for the function return registers: r0/d0, v0/w0.

Patch by Brendon Cahoon.

llvm-svn: 328120
This commit is contained in:
Krzysztof Parzyszek 2018-03-21 17:23:32 +00:00
parent 778032f39d
commit b4bb75d6ad
1 changed files with 38 additions and 18 deletions
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56
llvm/lib/Target/Hexagon/HexagonSubtarget.cpp
View File

@ -208,9 +208,11 @@ bool HexagonSubtarget::CallMutation::shouldTFRICallBind(
void HexagonSubtarget::CallMutation::apply(ScheduleDAGInstrs *DAGInstrs) {
ScheduleDAGMI *DAG = static_cast<ScheduleDAGMI*>(DAGInstrs);
SUnit* LastSequentialCall = nullptr;
unsigned VRegHoldingRet = 0;
unsigned RetRegister;
SUnit* LastUseOfRet = nullptr;
// Map from virtual register to physical register from the copy.
DenseMap<unsigned, unsigned> VRegHoldingReg;
// Map from the physical register to the instruction that uses virtual
// register. This is used to create the barrier edge.
DenseMap<unsigned, SUnit *> LastVRegUse;
auto &TRI = *DAG->MF.getSubtarget().getRegisterInfo();
auto &HII = *DAG->MF.getSubtarget<HexagonSubtarget>().getInstrInfo();
@ -227,8 +229,10 @@ void HexagonSubtarget::CallMutation::apply(ScheduleDAGInstrs *DAGInstrs) {
else if (SchedPredsCloser && LastSequentialCall && su > 1 && su < e-1 &&
shouldTFRICallBind(HII, DAG->SUnits[su], DAG->SUnits[su+1]))
DAG->addEdge(&DAG->SUnits[su], SDep(&DAG->SUnits[su-1], SDep::Barrier));
// Prevent redundant register copies between two calls, which are caused by
// both the return value and the argument for the next call being in %r0.
// Prevent redundant register copies due to reads and writes of physical
// registers. The original motivation for this was the code generated
// between two calls, which are caused both the return value and the
// argument for the next call being in %r0.
// Example:
// 1: <call1>
// 2: %vreg = COPY %r0
@ -237,21 +241,37 @@ void HexagonSubtarget::CallMutation::apply(ScheduleDAGInstrs *DAGInstrs) {
// 5: <call2>
// The scheduler would often swap 3 and 4, so an additional register is
// needed. This code inserts a Barrier dependence between 3 & 4 to prevent
// this. The same applies for %d0 and %v0/%w0, which are also handled.
// this.
// The code below checks for all the physical registers, not just R0/D0/V0.
else if (SchedRetvalOptimization) {
const MachineInstr *MI = DAG->SUnits[su].getInstr();
if (MI->isCopy() && (MI->readsRegister(Hexagon::R0, &TRI) ||
MI->readsRegister(Hexagon::V0, &TRI))) {
// %vreg = COPY %r0
VRegHoldingRet = MI->getOperand(0).getReg();
RetRegister = MI->getOperand(1).getReg();
LastUseOfRet = nullptr;
} else if (VRegHoldingRet && MI->readsVirtualRegister(VRegHoldingRet))
// <use of %X>
LastUseOfRet = &DAG->SUnits[su];
else if (LastUseOfRet && MI->definesRegister(RetRegister, &TRI))
// %r0 = ...
DAG->addEdge(&DAG->SUnits[su], SDep(LastUseOfRet, SDep::Barrier));
if (MI->isCopy() &&
TargetRegisterInfo::isPhysicalRegister(MI->getOperand(1).getReg())) {
// %vregX = COPY %r0
VRegHoldingReg[MI->getOperand(0).getReg()] = MI->getOperand(1).getReg();
LastVRegUse.erase(MI->getOperand(1).getReg());
} else {
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg())
continue;
if (MO.isUse() && !MI->isCopy() &&
VRegHoldingReg.count(MO.getReg())) {
// <use of %vregX>
LastVRegUse[VRegHoldingReg[MO.getReg()]] = &DAG->SUnits[su];
} else if (MO.isDef() &&
TargetRegisterInfo::isPhysicalRegister(MO.getReg())) {
for (MCRegAliasIterator AI(MO.getReg(), &TRI, true); AI.isValid();
++AI) {
if (LastVRegUse.count(*AI) &&
LastVRegUse[*AI] != &DAG->SUnits[su])
// %r0 = ...
DAG->addEdge(&DAG->SUnits[su], SDep(LastVRegUse[*AI], SDep::Barrier));
LastVRegUse.erase(*AI);
}
}
}
}
}
}
}