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Prefer multiplications to divisions. 

llvm-svn: 129080
This commit is contained in:
Jakob Stoklund Olesen 2011-04-07 17:27:48 +00:00
parent 6d2bbc1c20
commit 1c0db0fd21
1 changed files with 13 additions and 7 deletions
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20
llvm/lib/CodeGen/SpillPlacement.cpp
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@ -67,11 +67,11 @@ void SpillPlacement::getAnalysisUsage(AnalysisUsage &AU) const {
/// because all weights are positive.
///
struct SpillPlacement::Node {
/// Frequency - Total block frequency feeding into[0] or out of[1] the bundle.
/// Scale - Inverse block frequency feeding into[0] or out of[1] the bundle.
/// Ideally, these two numbers should be identical, but inaccuracies in the
/// block frequency estimates means that we need to normalize ingoing and
/// outgoing frequencies separately so they are commensurate.
float Frequency[2];
float Scale[2];
/// Bias - Normalized contributions from non-transparent blocks.
/// A bundle connected to a MustSpill block has a huge negative bias,
@ -107,7 +107,7 @@ struct SpillPlacement::Node {
/// Node - Create a blank Node.
Node() {
Frequency[0] = Frequency[1] = 0;
Scale[0] = Scale[1] = 0;
}
/// clear - Reset per-query data, but preserve frequencies that only depend on
@ -121,7 +121,7 @@ struct SpillPlacement::Node {
/// out=0 for an ingoing link, and 1 for an outgoing link.
void addLink(unsigned b, float w, bool out) {
// Normalize w relative to all connected blocks from that direction.
w /= Frequency[out];
w *= Scale[out];
// There can be multiple links to the same bundle, add them up.
for (LinkVector::iterator I = Links.begin(), E = Links.end(); I != E; ++I)
@ -137,7 +137,7 @@ struct SpillPlacement::Node {
/// Return the change to the total number of positive biases.
int addBias(float w, bool out) {
// Normalize w relative to all connected blocks from that direction.
w /= Frequency[out];
w *= Scale[out];
int Before = Bias > 0;
Bias += w;
int After = Bias > 0;
@ -185,10 +185,16 @@ bool SpillPlacement::runOnMachineFunction(MachineFunction &mf) {
loops->getLoopDepth(I));
unsigned Num = I->getNumber();
BlockFrequency[Num] = Freq;
nodes[bundles->getBundle(Num, 1)].Frequency[0] += Freq;
nodes[bundles->getBundle(Num, 0)].Frequency[1] += Freq;
nodes[bundles->getBundle(Num, 1)].Scale[0] += Freq;
nodes[bundles->getBundle(Num, 0)].Scale[1] += Freq;
}
// Scales are reciprocal frequencies.
for (unsigned i = 0, e = bundles->getNumBundles(); i != e; ++i)
for (unsigned d = 0; d != 2; ++d)
if (nodes[i].Scale[d] > 0)
nodes[i].Scale[d] = 1 / nodes[i].Scale[d];
// We never change the function.
return false;
}