[llvm] 1e4ee0b - [Dominators] Fixup comments in GenericDominatorTreeConstruction. NFC.
Jakub Kuderski via llvm-commits
llvm-commits at lists.llvm.org
Wed Mar 18 11:00:37 PDT 2020
Author: Jakub Kuderski
Date: 2020-03-18T13:59:58-04:00
New Revision: 1e4ee0bfc529cf7dce7a7c72d42dc207ba9df1d9
URL: https://github.com/llvm/llvm-project/commit/1e4ee0bfc529cf7dce7a7c72d42dc207ba9df1d9
DIFF: https://github.com/llvm/llvm-project/commit/1e4ee0bfc529cf7dce7a7c72d42dc207ba9df1d9.diff
LOG: [Dominators] Fixup comments in GenericDominatorTreeConstruction. NFC.
Reviewers: asbirlea, brzycki, NutshellySima, grosser
Reviewed By: asbirlea, NutshellySima
Subscribers: llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D76340
Added:
Modified:
llvm/include/llvm/Support/GenericDomTreeConstruction.h
Removed:
################################################################################
diff --git a/llvm/include/llvm/Support/GenericDomTreeConstruction.h b/llvm/include/llvm/Support/GenericDomTreeConstruction.h
index 7c0278e8770e..571550012374 100644
--- a/llvm/include/llvm/Support/GenericDomTreeConstruction.h
+++ b/llvm/include/llvm/Support/GenericDomTreeConstruction.h
@@ -7,11 +7,11 @@
//===----------------------------------------------------------------------===//
/// \file
///
-/// Generic dominator tree construction - This file provides routines to
+/// Generic dominator tree construction - this file provides routines to
/// construct immediate dominator information for a flow-graph based on the
/// Semi-NCA algorithm described in this dissertation:
///
-/// Linear-Time Algorithms for Dominators and Related Problems
+/// [1] Linear-Time Algorithms for Dominators and Related Problems
/// Loukas Georgiadis, Princeton University, November 2005, pp. 21-23:
/// ftp://ftp.cs.princeton.edu/reports/2005/737.pdf
///
@@ -20,13 +20,15 @@
///
/// O(n^2) worst cases happen when the computation of nearest common ancestors
/// requires O(n) average time, which is very unlikely in real world. If this
-/// ever turns out to be an issue, consider implementing a hybrid algorithm.
+/// ever turns out to be an issue, consider implementing a hybrid algorithm
+/// that uses SLT to perform full constructions and SemiNCA for incremental
+/// updates.
///
/// The file uses the Depth Based Search algorithm to perform incremental
/// updates (insertion and deletions). The implemented algorithm is based on
/// this publication:
///
-/// An Experimental Study of Dynamic Dominators
+/// [2] An Experimental Study of Dynamic Dominators
/// Loukas Georgiadis, et al., April 12 2016, pp. 5-7, 9-10:
/// https://arxiv.org/pdf/1604.02711.pdf
///
@@ -732,7 +734,7 @@ struct SemiNCAInfo {
LLVM_DEBUG(dbgs() << "Roots are
diff erent in updated trees\n"
<< "The entire tree needs to be rebuilt\n");
// It may be possible to update the tree without recalculating it, but
- // we do not know yet how to do it, and it happens rarely in practise.
+ // we do not know yet how to do it, and it happens rarely in practice.
CalculateFromScratch(DT, BUI);
}
}
@@ -757,13 +759,13 @@ struct SemiNCAInfo {
LLVM_DEBUG(dbgs() << "\t\tNCA == " << BlockNamePrinter(NCD) << "\n");
const unsigned NCDLevel = NCD->getLevel();
- // Based on Lemma 2.5 from the second paper, after insertion of (From,To), v
- // is affected iff depth(NCD)+1 < depth(v) && a path P from To to v exists
- // where every w on P s.t. depth(v) <= depth(w)
+ // Based on Lemma 2.5 from [2], after insertion of (From,To), v is affected
+ // iff depth(NCD)+1 < depth(v) && a path P from To to v exists where every
+ // w on P s.t. depth(v) <= depth(w)
//
// This reduces to a widest path problem (maximizing the depth of the
// minimum vertex in the path) which can be solved by a modified version of
- // Dijkstra with a bucket queue (named depth-based search in the paper).
+ // Dijkstra with a bucket queue (named depth-based search in [2]).
// To is in the path, so depth(NCD)+1 < depth(v) <= depth(To). Nothing
// affected if this does not hold.
@@ -957,7 +959,7 @@ struct SemiNCAInfo {
<< BlockNamePrinter(ToIDom) << "\n");
// To remains reachable after deletion.
- // (Based on the caption under Figure 4. from the second paper.)
+ // (Based on the caption under Figure 4. from [2].)
if (FromTN != ToIDom || HasProperSupport(DT, BUI, ToTN))
DeleteReachable(DT, BUI, FromTN, ToTN);
else
@@ -976,7 +978,7 @@ struct SemiNCAInfo {
LLVM_DEBUG(dbgs() << "\tRebuilding subtree\n");
// Find the top of the subtree that needs to be rebuilt.
- // (Based on the lemma 2.6 from the second paper.)
+ // (Based on the lemma 2.6 from [2].)
const NodePtr ToIDom =
DT.findNearestCommonDominator(FromTN->getBlock(), ToTN->getBlock());
assert(ToIDom || DT.isPostDominator());
@@ -1008,7 +1010,7 @@ struct SemiNCAInfo {
}
// Checks if a node has proper support, as defined on the page 3 and later
- // explained on the page 7 of the second paper.
+ // explained on the page 7 of [2].
static bool HasProperSupport(DomTreeT &DT, const BatchUpdatePtr BUI,
const TreeNodePtr TN) {
LLVM_DEBUG(dbgs() << "IsReachableFromIDom " << BlockNamePrinter(TN)
@@ -1033,7 +1035,7 @@ struct SemiNCAInfo {
}
// Handle deletions that make destination node unreachable.
- // (Based on the lemma 2.7 from the second paper.)
+ // (Based on the lemma 2.7 from the [2].)
static void DeleteUnreachable(DomTreeT &DT, const BatchUpdatePtr BUI,
const TreeNodePtr ToTN) {
LLVM_DEBUG(dbgs() << "Deleting unreachable subtree "
@@ -1493,9 +1495,9 @@ struct SemiNCAInfo {
// LEFT, and thus, LEFT is really an ancestor (in the dominator tree) of
// RIGHT, not a sibling.
- // It is possible to verify the parent and sibling properties in
- // linear time, but the algorithms are complex. Instead, we do it in a
- // straightforward N^2 and N^3 way below, using direct path reachability.
+ // It is possible to verify the parent and sibling properties in linear time,
+ // but the algorithms are complex. Instead, we do it in a straightforward
+ // N^2 and N^3 way below, using direct path reachability.
// Checks if the tree has the parent property: if for all edges from V to W in
// the input graph, such that V is reachable, the parent of W in the tree is
@@ -1571,7 +1573,7 @@ struct SemiNCAInfo {
// Check if the given tree is the same as a freshly computed one for the same
// Parent.
- // Running time: O(N^2), but faster in practise (same as tree construction).
+ // Running time: O(N^2), but faster in practice (same as tree construction).
//
// Note that this does not check if that the tree construction algorithm is
// correct and should be only used for fast (but possibly unsound)
@@ -1648,12 +1650,12 @@ bool Verify(const DomTreeT &DT, typename DomTreeT::VerificationLevel VL) {
if (!SNCA.IsSameAsFreshTree(DT))
return false;
- // Common checks to verify the properties of the tree. O(N log N) at worst
+ // Common checks to verify the properties of the tree. O(N log N) at worst.
if (!SNCA.verifyRoots(DT) || !SNCA.verifyReachability(DT) ||
!SNCA.VerifyLevels(DT) || !SNCA.VerifyDFSNumbers(DT))
return false;
- // Extra checks depending on VerificationLevel. Up to O(N^3)
+ // Extra checks depending on VerificationLevel. Up to O(N^3).
if (VL == DomTreeT::VerificationLevel::Basic ||
VL == DomTreeT::VerificationLevel::Full)
if (!SNCA.verifyParentProperty(DT))
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