[llvm-commits] [llvm] r157348 - /llvm/trunk/lib/CodeGen/BranchFolding.cpp
Bill Wendling
isanbard at gmail.com
Wed May 23 15:09:50 PDT 2012
Author: void
Date: Wed May 23 17:09:50 2012
New Revision: 157348
URL: http://llvm.org/viewvc/llvm-project?rev=157348&view=rev
Log:
Reduce indentation by early detection of 'continue'. No functionality change.
Modified:
llvm/trunk/lib/CodeGen/BranchFolding.cpp
Modified: llvm/trunk/lib/CodeGen/BranchFolding.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/BranchFolding.cpp?rev=157348&r1=157347&r2=157348&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/BranchFolding.cpp (original)
+++ llvm/trunk/lib/CodeGen/BranchFolding.cpp Wed May 23 17:09:50 2012
@@ -819,10 +819,8 @@
}
bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
-
- if (!EnableTailMerge) return false;
-
bool MadeChange = false;
+ if (!EnableTailMerge) return MadeChange;
// First find blocks with no successors.
MergePotentials.clear();
@@ -839,6 +837,7 @@
if (MergePotentials.size() == TailMergeThreshold)
for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i)
TriedMerging.insert(MergePotentials[i].getBlock());
+
// See if we can do any tail merging on those.
if (MergePotentials.size() >= 2)
MadeChange |= TryTailMergeBlocks(NULL, NULL);
@@ -864,88 +863,97 @@
for (MachineFunction::iterator I = llvm::next(MF.begin()), E = MF.end();
I != E; ++I) {
- if (I->pred_size() >= 2) {
- SmallPtrSet<MachineBasicBlock *, 8> UniquePreds;
- MachineBasicBlock *IBB = I;
- MachineBasicBlock *PredBB = prior(I);
- MergePotentials.clear();
- for (MachineBasicBlock::pred_iterator P = I->pred_begin(),
- E2 = I->pred_end();
- P != E2 && MergePotentials.size() < TailMergeThreshold; ++P) {
- MachineBasicBlock *PBB = *P;
- if (TriedMerging.count(PBB))
- continue;
- // Skip blocks that loop to themselves, can't tail merge these.
- if (PBB == IBB)
- continue;
- // Visit each predecessor only once.
- if (!UniquePreds.insert(PBB))
- continue;
- // Skip blocks which may jump to a landing pad. Can't tail merge these.
- if (PBB->getLandingPadSuccessor())
- continue;
- MachineBasicBlock *TBB = 0, *FBB = 0;
- SmallVector<MachineOperand, 4> Cond;
- if (!TII->AnalyzeBranch(*PBB, TBB, FBB, Cond, true)) {
- // Failing case: IBB is the target of a cbr, and
- // we cannot reverse the branch.
- SmallVector<MachineOperand, 4> NewCond(Cond);
- if (!Cond.empty() && TBB == IBB) {
- if (TII->ReverseBranchCondition(NewCond))
+ if (I->pred_size() >= 2) continue;
+ SmallPtrSet<MachineBasicBlock *, 8> UniquePreds;
+ MachineBasicBlock *IBB = I;
+ MachineBasicBlock *PredBB = prior(I);
+ MergePotentials.clear();
+ for (MachineBasicBlock::pred_iterator P = I->pred_begin(),
+ E2 = I->pred_end();
+ P != E2 && MergePotentials.size() < TailMergeThreshold; ++P) {
+ MachineBasicBlock *PBB = *P;
+ if (TriedMerging.count(PBB))
+ continue;
+
+ // Skip blocks that loop to themselves, can't tail merge these.
+ if (PBB == IBB)
+ continue;
+
+ // Visit each predecessor only once.
+ if (!UniquePreds.insert(PBB))
+ continue;
+
+ // Skip blocks which may jump to a landing pad. Can't tail merge these.
+ if (PBB->getLandingPadSuccessor())
+ continue;
+
+ MachineBasicBlock *TBB = 0, *FBB = 0;
+ SmallVector<MachineOperand, 4> Cond;
+ if (!TII->AnalyzeBranch(*PBB, TBB, FBB, Cond, true)) {
+ // Failing case: IBB is the target of a cbr, and we cannot reverse the
+ // branch.
+ SmallVector<MachineOperand, 4> NewCond(Cond);
+ if (!Cond.empty() && TBB == IBB) {
+ if (TII->ReverseBranchCondition(NewCond))
+ continue;
+ // This is the QBB case described above
+ if (!FBB)
+ FBB = llvm::next(MachineFunction::iterator(PBB));
+ }
+
+ // Failing case: the only way IBB can be reached from PBB is via
+ // exception handling. Happens for landing pads. Would be nice to have
+ // a bit in the edge so we didn't have to do all this.
+ if (IBB->isLandingPad()) {
+ MachineFunction::iterator IP = PBB; IP++;
+ MachineBasicBlock *PredNextBB = NULL;
+ if (IP != MF.end())
+ PredNextBB = IP;
+ if (TBB == NULL) {
+ if (IBB != PredNextBB) // fallthrough
+ continue;
+ } else if (FBB) {
+ if (TBB != IBB && FBB != IBB) // cbr then ubr
+ continue;
+ } else if (Cond.empty()) {
+ if (TBB != IBB) // ubr
+ continue;
+ } else {
+ if (TBB != IBB && IBB != PredNextBB) // cbr
continue;
- // This is the QBB case described above
- if (!FBB)
- FBB = llvm::next(MachineFunction::iterator(PBB));
- }
- // Failing case: the only way IBB can be reached from PBB is via
- // exception handling. Happens for landing pads. Would be nice
- // to have a bit in the edge so we didn't have to do all this.
- if (IBB->isLandingPad()) {
- MachineFunction::iterator IP = PBB; IP++;
- MachineBasicBlock *PredNextBB = NULL;
- if (IP != MF.end())
- PredNextBB = IP;
- if (TBB == NULL) {
- if (IBB != PredNextBB) // fallthrough
- continue;
- } else if (FBB) {
- if (TBB != IBB && FBB != IBB) // cbr then ubr
- continue;
- } else if (Cond.empty()) {
- if (TBB != IBB) // ubr
- continue;
- } else {
- if (TBB != IBB && IBB != PredNextBB) // cbr
- continue;
- }
- }
- // Remove the unconditional branch at the end, if any.
- if (TBB && (Cond.empty() || FBB)) {
- DebugLoc dl; // FIXME: this is nowhere
- TII->RemoveBranch(*PBB);
- if (!Cond.empty())
- // reinsert conditional branch only, for now
- TII->InsertBranch(*PBB, (TBB == IBB) ? FBB : TBB, 0, NewCond, dl);
}
- MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(PBB), *P));
}
+
+ // Remove the unconditional branch at the end, if any.
+ if (TBB && (Cond.empty() || FBB)) {
+ DebugLoc dl; // FIXME: this is nowhere
+ TII->RemoveBranch(*PBB);
+ if (!Cond.empty())
+ // reinsert conditional branch only, for now
+ TII->InsertBranch(*PBB, (TBB == IBB) ? FBB : TBB, 0, NewCond, dl);
+ }
+
+ MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(PBB), *P));
}
- // If this is a large problem, avoid visiting the same basic blocks
- // multiple times.
- if (MergePotentials.size() == TailMergeThreshold)
- for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i)
- TriedMerging.insert(MergePotentials[i].getBlock());
- if (MergePotentials.size() >= 2)
- MadeChange |= TryTailMergeBlocks(IBB, PredBB);
- // Reinsert an unconditional branch if needed.
- // The 1 below can occur as a result of removing blocks in
- // TryTailMergeBlocks.
- PredBB = prior(I); // this may have been changed in TryTailMergeBlocks
- if (MergePotentials.size() == 1 &&
- MergePotentials.begin()->getBlock() != PredBB)
- FixTail(MergePotentials.begin()->getBlock(), IBB, TII);
}
+
+ // If this is a large problem, avoid visiting the same basic blocks multiple
+ // times.
+ if (MergePotentials.size() == TailMergeThreshold)
+ for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i)
+ TriedMerging.insert(MergePotentials[i].getBlock());
+
+ if (MergePotentials.size() >= 2)
+ MadeChange |= TryTailMergeBlocks(IBB, PredBB);
+
+ // Reinsert an unconditional branch if needed. The 1 below can occur as a
+ // result of removing blocks in TryTailMergeBlocks.
+ PredBB = prior(I); // this may have been changed in TryTailMergeBlocks
+ if (MergePotentials.size() == 1 &&
+ MergePotentials.begin()->getBlock() != PredBB)
+ FixTail(MergePotentials.begin()->getBlock(), IBB, TII);
}
+
return MadeChange;
}
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