Generalize PostRAHazardRecognizer so it can be used in any pass for

both forward and backward scheduling. Rename it to
ScoreboardHazardRecognizer (Scoreboard is one word). Remove integer
division from the scoreboard's critical path.

llvm-svn: 121274

1 files changed, 191 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/ScoreboardHazardRecognizer.cpp b/llvm/lib/CodeGen/ScoreboardHazardRecognizer.cpp
new file mode 100644
index 00000000000..d78b5d3ecbd
--- /dev/null
+++ b/llvm/lib/CodeGen/ScoreboardHazardRecognizer.cpp
@@ -0,0 +1,191 @@
+//===----- ScoreboardHazardRecognizer.cpp - Scheduler Support -------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the ScoreboardHazardRecognizer class, which
+// encapsultes hazard-avoidance heuristics for scheduling, based on the
+// scheduling itineraries specified for the target.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "sched-hazard"
+#include "llvm/CodeGen/ScoreboardHazardRecognizer.h"
+#include "llvm/CodeGen/ScheduleDAG.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetInstrItineraries.h"
+
+using namespace llvm;
+
+ScoreboardHazardRecognizer::
+ScoreboardHazardRecognizer(const InstrItineraryData *LItinData) :
+  ScheduleHazardRecognizer(), ItinData(LItinData) {
+  // Determine the maximum depth of any itinerary. This determines the
+  // depth of the scoreboard. We always make the scoreboard at least 1
+  // cycle deep to avoid dealing with the boundary condition.
+  unsigned ScoreboardDepth = 1;
+  if (ItinData && !ItinData->isEmpty()) {
+    for (unsigned idx = 0; ; ++idx) {
+      if (ItinData->isEndMarker(idx))
+        break;
+
+      const InstrStage *IS = ItinData->beginStage(idx);
+      const InstrStage *E = ItinData->endStage(idx);
+      unsigned ItinDepth = 0;
+      for (; IS != E; ++IS)
+        ItinDepth += IS->getCycles();
+
+      // Find the next power-of-2 >= ItinDepth
+      while (ItinDepth > ScoreboardDepth) {
+        ScoreboardDepth *= 2;
+      }
+    }
+  }
+
+  ReservedScoreboard.reset(ScoreboardDepth);
+  RequiredScoreboard.reset(ScoreboardDepth);
+
+  DEBUG(dbgs() << "Using scoreboard hazard recognizer: Depth = "
+               << ScoreboardDepth << '\n');
+}
+
+void ScoreboardHazardRecognizer::Reset() {
+  RequiredScoreboard.reset();
+  ReservedScoreboard.reset();
+}
+
+void ScoreboardHazardRecognizer::Scoreboard::dump() const {
+  dbgs() << "Scoreboard:\n";
+
+  unsigned last = Depth - 1;
+  while ((last > 0) && ((*this)[last] == 0))
+    last--;
+
+  for (unsigned i = 0; i <= last; i++) {
+    unsigned FUs = (*this)[i];
+    dbgs() << "\t";
+    for (int j = 31; j >= 0; j--)
+      dbgs() << ((FUs & (1 << j)) ? '1' : '0');
+    dbgs() << '\n';
+  }
+}
+
+ScheduleHazardRecognizer::HazardType
+ScoreboardHazardRecognizer::getHazardType(SUnit *SU) {
+  if (!ItinData || ItinData->isEmpty())
+    return NoHazard;
+
+  unsigned cycle = 0;
+
+  // Use the itinerary for the underlying instruction to check for
+  // free FU's in the scoreboard at the appropriate future cycles.
+  unsigned idx = SU->getInstr()->getDesc().getSchedClass();
+  for (const InstrStage *IS = ItinData->beginStage(idx),
+         *E = ItinData->endStage(idx); IS != E; ++IS) {
+    // We must find one of the stage's units free for every cycle the
+    // stage is occupied. FIXME it would be more accurate to find the
+    // same unit free in all the cycles.
+    for (unsigned int i = 0; i < IS->getCycles(); ++i) {
+      assert(((cycle + i) < RequiredScoreboard.getDepth()) &&
+             "Scoreboard depth exceeded!");
+
+      unsigned freeUnits = IS->getUnits();
+      switch (IS->getReservationKind()) {
+      default:
+       assert(0 && "Invalid FU reservation");
+      case InstrStage::Required:
+        // Required FUs conflict with both reserved and required ones
+        freeUnits &= ~ReservedScoreboard[cycle + i];
+        // FALLTHROUGH
+      case InstrStage::Reserved:
+        // Reserved FUs can conflict only with required ones.
+        freeUnits &= ~RequiredScoreboard[cycle + i];
+        break;
+      }
+
+      if (!freeUnits) {
+        DEBUG(dbgs() << "*** Hazard in cycle " << (cycle + i) << ", ");
+        DEBUG(dbgs() << "SU(" << SU->NodeNum << "): ");
+        DEBUG(SU->getInstr()->dump());
+        return Hazard;
+      }
+    }
+
+    // Advance the cycle to the next stage.
+    cycle += IS->getNextCycles();
+  }
+
+  return NoHazard;
+}
+
+void ScoreboardHazardRecognizer::EmitInstruction(SUnit *SU) {
+  if (!ItinData || ItinData->isEmpty())
+    return;
+
+  unsigned cycle = 0;
+
+  // Use the itinerary for the underlying instruction to reserve FU's
+  // in the scoreboard at the appropriate future cycles.
+  unsigned idx = SU->getInstr()->getDesc().getSchedClass();
+  for (const InstrStage *IS = ItinData->beginStage(idx),
+         *E = ItinData->endStage(idx); IS != E; ++IS) {
+    // We must reserve one of the stage's units for every cycle the
+    // stage is occupied. FIXME it would be more accurate to reserve
+    // the same unit free in all the cycles.
+    for (unsigned int i = 0; i < IS->getCycles(); ++i) {
+      assert(((cycle + i) < RequiredScoreboard.getDepth()) &&
+             "Scoreboard depth exceeded!");
+
+      unsigned freeUnits = IS->getUnits();
+      switch (IS->getReservationKind()) {
+      default:
+       assert(0 && "Invalid FU reservation");
+      case InstrStage::Required:
+        // Required FUs conflict with both reserved and required ones
+        freeUnits &= ~ReservedScoreboard[cycle + i];
+        // FALLTHROUGH
+      case InstrStage::Reserved:
+        // Reserved FUs can conflict only with required ones.
+        freeUnits &= ~RequiredScoreboard[cycle + i];
+        break;
+      }
+
+      // reduce to a single unit
+      unsigned freeUnit = 0;
+      do {
+        freeUnit = freeUnits;
+        freeUnits = freeUnit & (freeUnit - 1);
+      } while (freeUnits);
+
+      assert(freeUnit && "No function unit available!");
+      if (IS->getReservationKind() == InstrStage::Required)
+        RequiredScoreboard[cycle + i] |= freeUnit;
+      else
+        ReservedScoreboard[cycle + i] |= freeUnit;
+    }
+
+    // Advance the cycle to the next stage.
+    cycle += IS->getNextCycles();
+  }
+
+  DEBUG(ReservedScoreboard.dump());
+  DEBUG(RequiredScoreboard.dump());
+}
+
+void ScoreboardHazardRecognizer::AdvanceCycle() {
+  ReservedScoreboard[0] = 0; ReservedScoreboard.advance();
+  RequiredScoreboard[0] = 0; RequiredScoreboard.advance();
+}
+
+void ScoreboardHazardRecognizer::RecedeCycle() {
+  ReservedScoreboard[ReservedScoreboard.getDepth()-1] = 0;
+  ReservedScoreboard.recede();
+  RequiredScoreboard[RequiredScoreboard.getDepth()-1] = 0;
+  RequiredScoreboard.recede();
+}