misched: DAG builder support for tracking register pressure within the current scheduling region.
The DAG builder is a convenient place to do it. Hopefully this is more
efficient than a separate traversal over the same region.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155456 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineScheduler.cpp b/lib/CodeGen/MachineScheduler.cpp
index 1d3241b..100137b 100644
--- a/lib/CodeGen/MachineScheduler.cpp
+++ b/lib/CodeGen/MachineScheduler.cpp
@@ -14,6 +14,7 @@
#define DEBUG_TYPE "misched"
+#include "RegisterPressure.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineScheduler.h"
#include "llvm/CodeGen/Passes.h"
@@ -149,6 +150,8 @@
LIS = &getAnalysis<LiveIntervals>();
const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
+ RegClassInfo.runOnMachineFunction(*MF);
+
// Select the scheduler, or set the default.
MachineSchedRegistry::ScheduleDAGCtor Ctor = MachineSchedOpt;
if (Ctor == useDefaultMachineSched) {
@@ -163,6 +166,9 @@
OwningPtr<ScheduleDAGInstrs> Scheduler(Ctor(this));
// Visit all machine basic blocks.
+ //
+ // TODO: Visit blocks in global postorder or postorder within the bottom-up
+ // loop tree. Then we can optionally compute global RegPressure.
for (MachineFunction::iterator MBB = MF->begin(), MBBEnd = MF->end();
MBB != MBBEnd; ++MBB) {
@@ -181,6 +187,7 @@
unsigned RemainingCount = MBB->size();
for(MachineBasicBlock::iterator RegionEnd = MBB->end();
RegionEnd != MBB->begin(); RegionEnd = Scheduler->begin()) {
+
// Avoid decrementing RegionEnd for blocks with no terminator.
if (RegionEnd != MBB->end()
|| TII->isSchedulingBoundary(llvm::prior(RegionEnd), MBB, *MF)) {
@@ -279,8 +286,13 @@
/// machine instructions while updating LiveIntervals.
class ScheduleDAGMI : public ScheduleDAGInstrs {
AliasAnalysis *AA;
+ RegisterClassInfo *RegClassInfo;
MachineSchedStrategy *SchedImpl;
+ // Register pressure in this region computed by buildSchedGraph.
+ IntervalPressure RegPressure;
+ RegPressureTracker RPTracker;
+
/// The top of the unscheduled zone.
MachineBasicBlock::iterator CurrentTop;
@@ -293,7 +305,8 @@
public:
ScheduleDAGMI(MachineSchedContext *C, MachineSchedStrategy *S):
ScheduleDAGInstrs(*C->MF, *C->MLI, *C->MDT, /*IsPostRA=*/false, C->LIS),
- AA(C->AA), SchedImpl(S), CurrentTop(), CurrentBottom(),
+ AA(C->AA), RegClassInfo(&C->RegClassInfo), SchedImpl(S),
+ RPTracker(RegPressure), CurrentTop(), CurrentBottom(),
NumInstrsScheduled(0) {}
~ScheduleDAGMI() {
@@ -303,7 +316,16 @@
MachineBasicBlock::iterator top() const { return CurrentTop; }
MachineBasicBlock::iterator bottom() const { return CurrentBottom; }
- /// Implement ScheduleDAGInstrs interface.
+ /// Implement the ScheduleDAGInstrs interface for handling the next scheduling
+ /// region. This covers all instructions in a block, while schedule() may only
+ /// cover a subset.
+ void enterRegion(MachineBasicBlock *bb,
+ MachineBasicBlock::iterator begin,
+ MachineBasicBlock::iterator end,
+ unsigned endcount);
+
+ /// Implement ScheduleDAGInstrs interface for scheduling a sequence of
+ /// reorderable instructions.
void schedule();
protected:
@@ -392,10 +414,32 @@
return true;
}
+/// enterRegion - Called back from MachineScheduler::runOnMachineFunction after
+/// crossing a scheduling boundary. [begin, end) includes all instructions in
+/// the region, including the boundary itself and single-instruction regions
+/// that don't get scheduled.
+void ScheduleDAGMI::enterRegion(MachineBasicBlock *bb,
+ MachineBasicBlock::iterator begin,
+ MachineBasicBlock::iterator end,
+ unsigned endcount)
+{
+ ScheduleDAGInstrs::enterRegion(bb, begin, end, endcount);
+ // Setup the register pressure tracker to begin tracking at the end of this
+ // region.
+ RPTracker.init(&MF, RegClassInfo, LIS, BB, end);
+}
+
/// schedule - Called back from MachineScheduler::runOnMachineFunction
-/// after setting up the current scheduling region.
+/// after setting up the current scheduling region. [RegionBegin, RegionEnd)
+/// only includes instructions that have DAG nodes, not scheduling boundaries.
void ScheduleDAGMI::schedule() {
- buildSchedGraph(AA);
+ while(RPTracker.getPos() != RegionEnd) {
+ bool Moved = RPTracker.recede();
+ assert(Moved && "Regpressure tracker cannot find RegionEnd"); (void)Moved;
+ }
+
+ // Build the DAG.
+ buildSchedGraph(AA, &RPTracker);
DEBUG(dbgs() << "********** MI Scheduling **********\n");
DEBUG(for (unsigned su = 0, e = SUnits.size(); su != e; ++su)