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authorChris Lattner <sabre@nondot.org>2004-04-13 15:21:18 +0000
committerChris Lattner <sabre@nondot.org>2004-04-13 15:21:18 +0000
commit1f62f82b05563df9c83094608de24ea581014d1e (patch)
tree5dfda8274fa7bacd112959831515de5a9a4de759 /lib
parent6491340bc1be9987753930530e58cba303d748dc (diff)
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Refactor code a bit to make it simpler and eliminate the goto
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12888 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib')
-rw-r--r--lib/Transforms/Utils/LoopSimplify.cpp58
1 files changed, 31 insertions, 27 deletions
diff --git a/lib/Transforms/Utils/LoopSimplify.cpp b/lib/Transforms/Utils/LoopSimplify.cpp
index 5acece8..e775907 100644
--- a/lib/Transforms/Utils/LoopSimplify.cpp
+++ b/lib/Transforms/Utils/LoopSimplify.cpp
@@ -469,6 +469,28 @@ static void VerifyExitBlocks(Loop *L) {
VerifyExitBlocks(*I);
}
+/// FindPHIToPartitionLoops - The first part of loop-nestification is to find a
+/// PHI node that tells us how to partition the loops.
+static PHINode *FindPHIToPartitionLoops(Loop *L) {
+ for (BasicBlock::iterator I = L->getHeader()->begin();
+ PHINode *PN = dyn_cast<PHINode>(I); ) {
+ ++I;
+ if (Value *V = hasConstantValue(PN)) {
+ // This is a degenerate PHI already, don't modify it!
+ PN->replaceAllUsesWith(V);
+ PN->getParent()->getInstList().erase(PN);
+ } else {
+ // Scan this PHI node looking for a use of the PHI node by itself.
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+ if (PN->getIncomingValue(i) == PN &&
+ L->contains(PN->getIncomingBlock(i)))
+ // We found something tasty to remove.
+ return PN;
+ }
+ }
+ return 0;
+}
+
/// SeparateNestedLoop - If this loop has multiple backedges, try to pull one of
/// them out into a nested loop. This is important for code that looks like
/// this:
@@ -488,36 +510,18 @@ static void VerifyExitBlocks(Loop *L) {
///
Loop *LoopSimplify::SeparateNestedLoop(Loop *L) {
BasicBlock *Header = L->getHeader();
+ PHINode *PN = FindPHIToPartitionLoops(L);
+ if (PN == 0) return 0; // No known way to partition.
+ // Pull out all predecessors that have varying values in the loop. This
+ // handles the case when a PHI node has multiple instances of itself as
+ // arguments.
std::vector<BasicBlock*> OuterLoopPreds;
- for (BasicBlock::iterator I = Header->begin();
- PHINode *PN = dyn_cast<PHINode>(I); ) {
- ++I;
- if (Value *V = hasConstantValue(PN)) {
- // This is a degenerate PHI already, don't modify it!
- PN->replaceAllUsesWith(V);
- Header->getInstList().erase(PN);
- continue;
- }
-
- // Scan this PHI node looking for a use of the PHI node by itself.
- for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
- if (PN->getIncomingValue(i) == PN &&
- L->contains(PN->getIncomingBlock(i))) {
- // Wow, we found something tasty to remove. Pull out all predecessors
- // that have varying values in the loop. This handles the case when a
- // PHI node has multiple instances of itself as arguments.
- for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
- if (PN->getIncomingValue(i) != PN ||
- !L->contains(PN->getIncomingBlock(i)))
- OuterLoopPreds.push_back(PN->getIncomingBlock(i));
- goto FoundExtraction;
- }
- }
-
- return 0; // Nothing looks appetizing to separate out
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+ if (PN->getIncomingValue(i) != PN ||
+ !L->contains(PN->getIncomingBlock(i)))
+ OuterLoopPreds.push_back(PN->getIncomingBlock(i));
-FoundExtraction:
BasicBlock *NewBB = SplitBlockPredecessors(Header, ".outer", OuterLoopPreds);
// Update dominator information (set, immdom, domtree, and domfrontier)