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Add documentation for new backedge mass propagation in irregular loops.

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Tweak test cases and rename headerIndexFor -> getHeaderIndex.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239915 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Diego Novillo
2015-06-17 16:28:22 +00:00
parent b306ae3bf3
commit 5057ee8357
4 changed files with 17 additions and 87 deletions
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13
include/llvm/Analysis/BlockFrequencyInfoImpl.h
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@@ -226,7 +226,7 @@ public:
BlockNode getHeader() const { return Nodes[0]; }
bool isIrreducible() const { return NumHeaders > 1; }
HeaderMassList::difference_type headerIndexFor(const BlockNode &B) {
HeaderMassList::difference_type getHeaderIndex(const BlockNode &B) {
assert(isHeader(B) && "this is only valid on loop header blocks");
if (isIrreducible())
return std::lower_bound(Nodes.begin(), Nodes.begin() + NumHeaders, B) -
@@ -716,6 +716,17 @@ void IrreducibleGraph::addEdges(const BlockNode &Node,
/// - Distribute the mass accordingly, dithering to minimize mass loss,
/// as described in \a distributeMass().
///
/// In the case of irreducible loops, instead of a single loop header,
/// there will be several. The computation of backedge masses is similar
/// but instead of having a single backedge mass, there will be one
/// backedge per loop header. In these cases, each backedge will carry
/// a mass proportional to the edge weights along the corresponding
/// path.
///
/// At the end of propagation, the full mass assigned to the loop will be
/// distributed among the loop headers proportionally according to the
/// mass flowing through their backedges.
///
/// Finally, calculate the loop scale from the accumulated backedge mass.
///
/// 3. Distribute mass in the function (\a computeMassInFunction()).