[llvm-commits] CVS: llvm/lib/Analysis/LoopInfo.cpp
Chris Lattner
lattner at cs.uiuc.edu
Thu Sep 26 00:33:02 PDT 2002
Changes in directory llvm/lib/Analysis:
LoopInfo.cpp updated: 1.21 -> 1.22
---
Log message:
- Add new methods to LoopInfo: getLoopPreheader, addBasicBlockToLoop.
These allow extra information to be easily gathered, and loopinfo to be
updated.
---
Diffs of the changes:
Index: llvm/lib/Analysis/LoopInfo.cpp
diff -u llvm/lib/Analysis/LoopInfo.cpp:1.21 llvm/lib/Analysis/LoopInfo.cpp:1.22
--- llvm/lib/Analysis/LoopInfo.cpp:1.21 Mon Aug 26 11:43:42 2002
+++ llvm/lib/Analysis/LoopInfo.cpp Thu Sep 26 00:32:50 2002
@@ -81,7 +81,7 @@
}
Loop *LoopInfo::ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS) {
- if (BBMap.find(BB) != BBMap.end()) return 0; // Havn't processed this node?
+ if (BBMap.find(BB) != BBMap.end()) return 0; // Haven't processed this node?
std::vector<BasicBlock *> TodoStack;
@@ -127,4 +127,54 @@
}
return L;
+}
+
+/// getLoopPreheader - If there is a preheader for this loop, return it. A
+/// loop has a preheader if there is only one edge to the header of the loop
+/// from outside of the loop. If this is the case, the block branching to the
+/// header of the loop is the preheader node. The "preheaders" pass can be
+/// "Required" to ensure that there is always a preheader node for every loop.
+///
+/// This method returns null if there is no preheader for the loop (either
+/// because the loop is dead or because multiple blocks branch to the header
+/// node of this loop).
+///
+BasicBlock *Loop::getLoopPreheader() const {
+ // Keep track of nodes outside the loop branching to the header...
+ BasicBlock *Out = 0;
+
+ // Loop over the predecessors of the header node...
+ BasicBlock *Header = getHeader();
+ for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header);
+ PI != PE; ++PI)
+ if (!contains(*PI)) { // If the block is not in the loop...
+ if (Out) return 0; // Multiple predecessors outside the loop
+ Out = *PI;
+ }
+
+ // If there is exactly one preheader, return it. If there was zero, then Out
+ // is still null.
+ return Out;
+}
+
+/// addBasicBlockToLoop - This function is used by other analyses to update loop
+/// information. NewBB is set to be a new member of the current loop. Because
+/// of this, it is added as a member of all parent loops, and is added to the
+/// specified LoopInfo object as being in the current basic block. It is not
+/// valid to replace the loop header with this method.
+///
+void Loop::addBasicBlockToLoop(BasicBlock *NewBB, LoopInfo &LI) {
+ assert(LI[getHeader()] == this && "Incorrect LI specified for this loop!");
+ assert(NewBB && "Cannot add a null basic block to the loop!");
+ assert(LI[NewBB] == 0 && "BasicBlock already in the loop!");
+
+ // Add the loop mapping to the LoopInfo object...
+ LI.BBMap[NewBB] = this;
+
+ // Add the basic block to this loop and all parent loops...
+ Loop *L = this;
+ while (L) {
+ L->Blocks.push_back(NewBB);
+ L = L->getParentLoop();
+ }
}
More information about the llvm-commits
mailing list