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author | Chris Lattner <sabre@nondot.org> | 2004-04-13 15:21:18 +0000 |
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committer | Chris Lattner <sabre@nondot.org> | 2004-04-13 15:21:18 +0000 |
commit | 1f62f82b05563df9c83094608de24ea581014d1e (patch) | |
tree | 5dfda8274fa7bacd112959831515de5a9a4de759 /lib | |
parent | 6491340bc1be9987753930530e58cba303d748dc (diff) | |
download | external_llvm-1f62f82b05563df9c83094608de24ea581014d1e.zip external_llvm-1f62f82b05563df9c83094608de24ea581014d1e.tar.gz external_llvm-1f62f82b05563df9c83094608de24ea581014d1e.tar.bz2 |
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.cpp | 58 |
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) |