Imported Upstream version 5.18.0.246

Former-commit-id: 0c7ce5b1a7851e13f22acfd379b7f9fb304e4833

external/llvm/lib/CodeGen/LiveIntervalUnion.cpp

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+//===- LiveIntervalUnion.cpp - Live interval union data structure ---------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// LiveIntervalUnion represents a coalesced set of live intervals. This may be
+// used during coalescing to represent a congruence class, or during register
+// allocation to model liveness of a physical register.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/LiveIntervalUnion.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SparseBitVector.h"
+#include "llvm/CodeGen/LiveInterval.h"
+#include "llvm/CodeGen/TargetRegisterInfo.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cassert>
+#include <cstdlib>
+
+using namespace llvm;
+
+#define DEBUG_TYPE "regalloc"
+
+// Merge a LiveInterval's segments. Guarantee no overlaps.
+void LiveIntervalUnion::unify(LiveInterval &VirtReg, const LiveRange &Range) {
+  if (Range.empty())
+    return;
+  ++Tag;
+
+  // Insert each of the virtual register's live segments into the map.
+  LiveRange::const_iterator RegPos = Range.begin();
+  LiveRange::const_iterator RegEnd = Range.end();
+  SegmentIter SegPos = Segments.find(RegPos->start);
+
+  while (SegPos.valid()) {
+    SegPos.insert(RegPos->start, RegPos->end, &VirtReg);
+    if (++RegPos == RegEnd)
+      return;
+    SegPos.advanceTo(RegPos->start);
+  }
+
+  // We have reached the end of Segments, so it is no longer necessary to search
+  // for the insertion position.
+  // It is faster to insert the end first.
+  --RegEnd;
+  SegPos.insert(RegEnd->start, RegEnd->end, &VirtReg);
+  for (; RegPos != RegEnd; ++RegPos, ++SegPos)
+    SegPos.insert(RegPos->start, RegPos->end, &VirtReg);
+}
+
+// Remove a live virtual register's segments from this union.
+void LiveIntervalUnion::extract(LiveInterval &VirtReg, const LiveRange &Range) {
+  if (Range.empty())
+    return;
+  ++Tag;
+
+  // Remove each of the virtual register's live segments from the map.
+  LiveRange::const_iterator RegPos = Range.begin();
+  LiveRange::const_iterator RegEnd = Range.end();
+  SegmentIter SegPos = Segments.find(RegPos->start);
+
+  while (true) {
+    assert(SegPos.value() == &VirtReg && "Inconsistent LiveInterval");
+    SegPos.erase();
+    if (!SegPos.valid())
+      return;
+
+    // Skip all segments that may have been coalesced.
+    RegPos = Range.advanceTo(RegPos, SegPos.start());
+    if (RegPos == RegEnd)
+      return;
+
+    SegPos.advanceTo(RegPos->start);
+  }
+}
+
+void
+LiveIntervalUnion::print(raw_ostream &OS, const TargetRegisterInfo *TRI) const {
+  if (empty()) {
+    OS << " empty\n";
+    return;
+  }
+  for (LiveSegments::const_iterator SI = Segments.begin(); SI.valid(); ++SI) {
+    OS << " [" << SI.start() << ' ' << SI.stop() << "):"
+       << printReg(SI.value()->reg, TRI);
+  }
+  OS << '\n';
+}
+
+#ifndef NDEBUG
+// Verify the live intervals in this union and add them to the visited set.
+void LiveIntervalUnion::verify(LiveVirtRegBitSet& VisitedVRegs) {
+  for (SegmentIter SI = Segments.begin(); SI.valid(); ++SI)
+    VisitedVRegs.set(SI.value()->reg);
+}
+#endif //!NDEBUG
+
+// Scan the vector of interfering virtual registers in this union. Assume it's
+// quite small.
+bool LiveIntervalUnion::Query::isSeenInterference(LiveInterval *VirtReg) const {
+  return is_contained(InterferingVRegs, VirtReg);
+}
+
+// Collect virtual registers in this union that interfere with this
+// query's live virtual register.
+//
+// The query state is one of:
+//
+// 1. CheckedFirstInterference == false: Iterators are uninitialized.
+// 2. SeenAllInterferences == true: InterferingVRegs complete, iterators unused.
+// 3. Iterators left at the last seen intersection.
+//
+unsigned LiveIntervalUnion::Query::
+collectInterferingVRegs(unsigned MaxInterferingRegs) {
+  // Fast path return if we already have the desired information.
+  if (SeenAllInterferences || InterferingVRegs.size() >= MaxInterferingRegs)
+    return InterferingVRegs.size();
+
+  // Set up iterators on the first call.
+  if (!CheckedFirstInterference) {
+    CheckedFirstInterference = true;
+
+    // Quickly skip interference check for empty sets.
+    if (LR->empty() || LiveUnion->empty()) {
+      SeenAllInterferences = true;
+      return 0;
+    }
+
+    // In most cases, the union will start before LR.
+    LRI = LR->begin();
+    LiveUnionI.setMap(LiveUnion->getMap());
+    LiveUnionI.find(LRI->start);
+  }
+
+  LiveRange::const_iterator LREnd = LR->end();
+  LiveInterval *RecentReg = nullptr;
+  while (LiveUnionI.valid()) {
+    assert(LRI != LREnd && "Reached end of LR");
+
+    // Check for overlapping interference.
+    while (LRI->start < LiveUnionI.stop() && LRI->end > LiveUnionI.start()) {
+      // This is an overlap, record the interfering register.
+      LiveInterval *VReg = LiveUnionI.value();
+      if (VReg != RecentReg && !isSeenInterference(VReg)) {
+        RecentReg = VReg;
+        InterferingVRegs.push_back(VReg);
+        if (InterferingVRegs.size() >= MaxInterferingRegs)
+          return InterferingVRegs.size();
+      }
+      // This LiveUnion segment is no longer interesting.
+      if (!(++LiveUnionI).valid()) {
+        SeenAllInterferences = true;
+        return InterferingVRegs.size();
+      }
+    }
+
+    // The iterators are now not overlapping, LiveUnionI has been advanced
+    // beyond LRI.
+    assert(LRI->end <= LiveUnionI.start() && "Expected non-overlap");
+
+    // Advance the iterator that ends first.
+    LRI = LR->advanceTo(LRI, LiveUnionI.start());
+    if (LRI == LREnd)
+      break;
+
+    // Detect overlap, handle above.
+    if (LRI->start < LiveUnionI.stop())
+      continue;
+
+    // Still not overlapping. Catch up LiveUnionI.
+    LiveUnionI.advanceTo(LRI->start);
+  }
+  SeenAllInterferences = true;
+  return InterferingVRegs.size();
+}
+
+void LiveIntervalUnion::Array::init(LiveIntervalUnion::Allocator &Alloc,
+                                    unsigned NSize) {
+  // Reuse existing allocation.
+  if (NSize == Size)
+    return;
+  clear();
+  Size = NSize;
+  LIUs = static_cast<LiveIntervalUnion*>(
+    malloc(sizeof(LiveIntervalUnion)*NSize));
+  for (unsigned i = 0; i != Size; ++i)
+    new(LIUs + i) LiveIntervalUnion(Alloc);
+}
+
+void LiveIntervalUnion::Array::clear() {
+  if (!LIUs)
+    return;
+  for (unsigned i = 0; i != Size; ++i)
+    LIUs[i].~LiveIntervalUnion();
+  free(LIUs);
+  Size =  0;
+  LIUs = nullptr;
+}