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improve deletion of blocks that just contain branches by knowing that

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the pred block doesn't fall through into them if it's a jumptable.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@31263 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2006-10-28 17:32:47 +00:00
parent c24ff8ed12
commit cf420cca57
1 changed files with 38 additions and 33 deletions
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9
lib/CodeGen/BranchFolding.cpp
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@@ -534,10 +534,14 @@ void BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
// completely eliminate the block is when the block before this one
// falls through into MBB and we can't understand the prior block's branch
// condition.
if (MBB->empty() && (!PriorUnAnalyzable || !PrevBB.isSuccessor(MBB))) {
if (MBB->empty()) {
bool PredHasNoFallThrough = TII->BlockHasNoFallThrough(PrevBB);
if (PredHasNoFallThrough || !PriorUnAnalyzable ||
!PrevBB.isSuccessor(MBB)) {
// If the prior block falls through into us, turn it into an
// explicit branch to us to make updates simpler.
if (PrevBB.isSuccessor(MBB) && PriorTBB != MBB && PriorFBB != MBB) {
if (!PredHasNoFallThrough && PrevBB.isSuccessor(MBB) &&
PriorTBB != MBB && PriorFBB != MBB) {
if (PriorTBB == 0) {
assert(PriorCond.empty() && PriorFBB == 0 && "Bad branch analysis");
PriorTBB = MBB;
@@ -573,6 +577,7 @@ void BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
if (!HasBranchToSelf) return;
}
}
}
// Add the branch back if the block is more than just an uncond branch.
TII->InsertBranch(*MBB, CurTBB, 0, CurCond);