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rip out isExitBlockDominatedByBlockInLoop, calling DomTree::dominates instead.

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isExitBlockDominatedByBlockInLoop is a relic of the days when domtree was 
*just* a tree and didn't have DFS numbers.  Checking DFS numbers is faster
and easier than "limiting the search of the tree".


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122702 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2011-01-02 18:45:39 +00:00
parent bdce5720ad
commit 83fc584ea8
1 changed files with 4 additions and 37 deletions
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41
lib/Transforms/Scalar/LICM.cpp
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@ -137,38 +137,6 @@ namespace {
return false;
}
/// isExitBlockDominatedByBlockInLoop - This method checks to see if the
/// specified exit block of the loop is dominated by the specified block
/// that is in the body of the loop. We use these constraints to
/// dramatically limit the amount of the dominator tree that needs to be
/// searched.
bool isExitBlockDominatedByBlockInLoop(BasicBlock *ExitBlock,
BasicBlock *BlockInLoop) const {
// If the block in the loop is the loop header, it must be dominated!
BasicBlock *LoopHeader = CurLoop->getHeader();
if (BlockInLoop == LoopHeader)
return true;
DomTreeNode *BlockInLoopNode = DT->getNode(BlockInLoop);
DomTreeNode *IDom = DT->getNode(ExitBlock);
// Because the exit block is not in the loop, we know we have to get _at
// least_ its immediate dominator.
IDom = IDom->getIDom();
while (IDom && IDom != BlockInLoopNode) {
// If we have got to the header of the loop, then the instructions block
// did not dominate the exit node, so we can't hoist it.
if (IDom->getBlock() == LoopHeader)
return false;
// Get next Immediate Dominator.
IDom = IDom->getIDom();
};
return true;
}
/// sink - When an instruction is found to only be used outside of the loop,
/// this function moves it to the exit blocks and patches up SSA form as
/// needed.
@ -480,7 +448,7 @@ void LICM::sink(Instruction &I) {
// enough that we handle it as a special (more efficient) case. It is more
// efficient to handle because there are no PHI nodes that need to be placed.
if (ExitBlocks.size() == 1) {
if (!isExitBlockDominatedByBlockInLoop(ExitBlocks[0], I.getParent())) {
if (!DT->dominates(I.getParent(), ExitBlocks[0])) {
// Instruction is not used, just delete it.
CurAST->deleteValue(&I);
// If I has users in unreachable blocks, eliminate.
@ -531,7 +499,7 @@ void LICM::sink(Instruction &I) {
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
BasicBlock *ExitBlock = ExitBlocks[i];
if (!isExitBlockDominatedByBlockInLoop(ExitBlock, InstOrigBB))
if (!DT->dominates(InstOrigBB, ExitBlock))
continue;
// Insert the code after the last PHI node.
@ -622,10 +590,9 @@ bool LICM::isSafeToExecuteUnconditionally(Instruction &Inst) {
SmallVector<BasicBlock*, 8> ExitBlocks;
CurLoop->getExitBlocks(ExitBlocks);
// For each exit block, get the DT node and walk up the DT until the
// instruction's basic block is found or we exit the loop.
// Verify that the block dominates each of the exit blocks of the loop.
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
if (!isExitBlockDominatedByBlockInLoop(ExitBlocks[i], Inst.getParent()))
if (!DT->dominates(Inst.getParent(), ExitBlocks[i]))
return false;
return true;