Add source-level dominators analysis. Patch by Guoping Long!
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@142885 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/Dominators.cpp b/lib/Analysis/Dominators.cpp
new file mode 100644
index 0000000..62b7228
--- /dev/null
+++ b/lib/Analysis/Dominators.cpp
@@ -0,0 +1,160 @@
+//==- Dominators.cpp - Construct the Dominance Tree Given CFG ----*- C++ --*-==//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements a simple, fast dominance algorithm for source-level CFGs.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Analysis/Analyses/Dominators.h"
+#include "clang/Analysis/CFG.h"
+#include "clang/Analysis/AnalysisContext.h"
+#include "clang/Analysis/Analyses/PostOrderCFGView.h"
+
+using namespace clang;
+
+DominatorTree::~DominatorTree() {
+ IDoms.clear();
+ RootNode = 0;
+}
+
+CFGBlock * DominatorTree::getNode(const CFGBlock *B) const {
+ CFGBlockMapTy::const_iterator I = IDoms.find(B);
+ return I != IDoms.end() ? I->second : 0;
+}
+
+bool DominatorTree::properlyDominates(const CFGBlock *A,
+ const CFGBlock *B) const {
+ if (0 == A || 0 == B || A == B)
+ return false;
+
+ // The EntryBlock dominates every other block.
+ if (A == RootNode)
+ return true;
+
+ // Note: The dominator of the EntryBlock is itself.
+ CFGBlock *IDom = getNode(B);
+ while (IDom != A && IDom != RootNode)
+ IDom = getNode(IDom);
+
+ return IDom != RootNode;
+}
+
+bool DominatorTree::dominates(const CFGBlock *A,
+ const CFGBlock *B) const {
+ if (A == B)
+ return true;
+
+ return properlyDominates(A, B);
+}
+
+const CFGBlock * DominatorTree::findNearestCommonDominator
+ (const CFGBlock *A, const CFGBlock *B) const {
+ //If A dominates B, then A is the nearest common dominator
+ if (dominates(A, B))
+ return A;
+
+ //If B dominates A, then B is the nearest common dominator
+ if (dominates(B, A))
+ return B;
+
+ //Collect all A's dominators
+ llvm::SmallPtrSet<CFGBlock *, 16> ADoms;
+ ADoms.insert(RootNode);
+ CFGBlock *ADom = getNode(A);
+ while (ADom != RootNode) {
+ ADoms.insert(ADom);
+ ADom = getNode(ADom);
+ }
+
+ //Check all B's dominators against ADoms
+ CFGBlock *BDom = getNode(B);
+ while (BDom != RootNode){
+ if (ADoms.count(BDom) != 0)
+ return BDom;
+
+ BDom = getNode(BDom);
+ }
+
+ //The RootNode dominates every other node
+ return RootNode;
+}
+
+/// Constructs immediate dominator tree for a given CFG based on the algorithm
+/// described in this paper:
+///
+/// A Simple, Fast Dominance Algorithm
+/// Keith D. Cooper, Timothy J. Harvey and Ken Kennedy
+/// Software-Practice and Expreience, 2001;4:1-10.
+///
+/// This implementation is simple and runs faster in practice than the classis
+/// Lengauer-Tarjan algorithm. For detailed discussions, refer to the paper.
+void DominatorTree::BuildDominatorTree() {
+ CFG *cfg = AC.getCFG();
+ CFGBlock *EntryBlk = &cfg->getEntry();
+
+ //Sort all CFGBlocks in reverse order
+ PostOrderCFGView *rpocfg = AC.getAnalysis<PostOrderCFGView>();
+
+ //Set the root of the dominance tree
+ RootNode = EntryBlk;
+
+ //Compute the immediate dominator for each CFGBlock
+ IDoms[EntryBlk] = EntryBlk;
+ bool changed = true;
+ while (changed){
+ changed = false;
+
+ for (PostOrderCFGView::iterator I = rpocfg->begin(),
+ E = rpocfg->end(); I != E; ++I){
+ if (EntryBlk == *I)
+ continue;
+ if (const CFGBlock *B = *I) {
+ //Compute immediate dominance information for CFGBlock B
+ CFGBlock *IDom = 0;
+ for (CFGBlock::const_pred_iterator J = B->pred_begin(),
+ K = B->pred_end(); J != K; ++J)
+ if( CFGBlock *P = *J) {
+ if (IDoms.find(P) == IDoms.end())
+ continue;
+ if (!IDom)
+ IDom = P;
+ else {
+ //intersect IDom and P
+ CFGBlock *B1 = IDom, *B2 = P;
+ while (B1 != B2) {
+ while ((rpocfg->getComparator())(B2,B1))
+ B1 = IDoms[B1];
+ while ((rpocfg->getComparator())(B1,B2))
+ B2 = IDoms[B2];
+ }
+ IDom = B1;
+ }
+ }
+ if (IDoms[B] != IDom) {
+ IDoms[B] = IDom;
+ changed = true;
+ }
+ }
+ }
+ }//while
+}
+
+void DominatorTree::dump() {
+ CFG *cfg = AC.getCFG();
+
+ llvm::errs() << "Immediate dominance tree (Node#,IDom#):\n";
+ for (CFG::const_iterator I = cfg->begin(),
+ E = cfg->end(); I != E; ++I) {
+ assert(IDoms[(*I)] &&
+ "Failed to find the immediate dominator for all CFG blocks.");
+ llvm::errs() << "(" << (*I)->getBlockID()
+ << "," << IDoms[(*I)]->getBlockID() << ")\n";
+ }
+}
+