//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "spillplacement"
#include "SpillPlacement.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/CodeGen/EdgeBundles.h"
using namespace llvm;
+#define DEBUG_TYPE "spillplacement"
+
char SpillPlacement::ID = 0;
INITIALIZE_PASS_BEGIN(SpillPlacement, "spill-code-placement",
"Spill Code Placement Analysis", true, true)
MachineFunctionPass::getAnalysisUsage(AU);
}
+namespace {
+static BlockFrequency Threshold;
+}
+
/// Decision threshold. A node gets the output value 0 if the weighted sum of
/// its inputs falls in the open interval (-Threshold;Threshold).
-static const BlockFrequency Threshold = 2;
+static BlockFrequency getThreshold() { return Threshold; }
+
+/// \brief Set the threshold for a given entry frequency.
+///
+/// Set the threshold relative to \c Entry. Since the threshold is used as a
+/// bound on the open interval (-Threshold;Threshold), 1 is the minimum
+/// threshold.
+static void setThreshold(const BlockFrequency &Entry) {
+ // Apparently 2 is a good threshold when Entry==2^14, but we need to scale
+ // it. Divide by 2^13, rounding as appropriate.
+ uint64_t Freq = Entry.getFrequency();
+ uint64_t Scaled = (Freq >> 13) + bool(Freq & (1 << 12));
+ Threshold = std::max(UINT64_C(1), Scaled);
+}
/// Node - Each edge bundle corresponds to a Hopfield node.
///
// the CFG.
void clear() {
BiasN = BiasP = Value = 0;
- SumLinkWeights = Threshold;
+ SumLinkWeights = getThreshold();
Links.clear();
}
// 2. It helps tame rounding errors when the links nominally sum to 0.
//
bool Before = preferReg();
- if (SumN >= SumP + Threshold)
+ if (SumN >= SumP + getThreshold())
Value = -1;
- else if (SumP >= SumN + Threshold)
+ else if (SumP >= SumN + getThreshold())
Value = 1;
else
Value = 0;
// Compute total ingoing and outgoing block frequencies for all bundles.
BlockFrequencies.resize(mf.getNumBlockIDs());
- MachineBlockFrequencyInfo &MBFI = getAnalysis<MachineBlockFrequencyInfo>();
+ MBFI = &getAnalysis<MachineBlockFrequencyInfo>();
+ setThreshold(MBFI->getEntryFreq());
for (MachineFunction::iterator I = mf.begin(), E = mf.end(); I != E; ++I) {
unsigned Num = I->getNumber();
- BlockFrequencies[Num] = MBFI.getBlockFreq(I);
+ BlockFrequencies[Num] = MBFI->getBlockFreq(I);
}
// We never change the function.
void SpillPlacement::releaseMemory() {
delete[] nodes;
- nodes = 0;
+ nodes = nullptr;
}
/// activate - mark node n as active if it wasn't already.
// Hopfield network.
if (bundles->getBlocks(n).size() > 100) {
nodes[n].BiasP = 0;
- nodes[n].BiasN = (BlockFrequency::getEntryFrequency() / 16);
+ nodes[n].BiasN = (MBFI->getEntryFreq() / 16);
}
}
// affect the entire network in a single iteration. That means very fast
// convergence, usually in a single iteration.
for (unsigned iteration = 0; iteration != 10; ++iteration) {
- // Scan backwards, skipping the last node which was just updated.
+ // Scan backwards, skipping the last node when iteration is not zero. When
+ // iteration is not zero, the last node was just updated.
bool Changed = false;
for (SmallVectorImpl<unsigned>::const_reverse_iterator I =
- llvm::next(Linked.rbegin()), E = Linked.rend(); I != E; ++I) {
+ iteration == 0 ? Linked.rbegin() : std::next(Linked.rbegin()),
+ E = Linked.rend(); I != E; ++I) {
unsigned n = *I;
if (nodes[n].update(nodes)) {
Changed = true;
// Scan forwards, skipping the first node which was just updated.
Changed = false;
for (SmallVectorImpl<unsigned>::const_iterator I =
- llvm::next(Linked.begin()), E = Linked.end(); I != E; ++I) {
+ std::next(Linked.begin()), E = Linked.end(); I != E; ++I) {
unsigned n = *I;
if (nodes[n].update(nodes)) {
Changed = true;
ActiveNodes->reset(n);
Perfect = false;
}
- ActiveNodes = 0;
+ ActiveNodes = nullptr;
return Perfect;
}