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Do not lose branch weights when lowering SwitchInst.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136529 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakub Staszak
2011-07-29 22:25:21 +00:00
parent 9162abb39f
commit c8f34de5d6
2 changed files with 52 additions and 17 deletions
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43
lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
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@@ -1282,10 +1282,12 @@ uint32_t SelectionDAGBuilder::getEdgeWeight(MachineBasicBlock *Src,
return BPI->getEdgeWeight(SrcBB, DstBB);
}
void SelectionDAGBuilder::addSuccessorWithWeight(MachineBasicBlock *Src,
MachineBasicBlock *Dst) {
uint32_t weight = getEdgeWeight(Src, Dst);
Src->addSuccessor(Dst, weight);
void SelectionDAGBuilder::
addSuccessorWithWeight(MachineBasicBlock *Src, MachineBasicBlock *Dst,
uint32_t Weight /* = 0 */) {
if (!Weight)
Weight = getEdgeWeight(Src, Dst);
Src->addSuccessor(Dst, Weight);
}
@@ -1558,8 +1560,8 @@ void SelectionDAGBuilder::visitSwitchCase(CaseBlock &CB,
}
// Update successor info
addSuccessorWithWeight(SwitchBB, CB.TrueBB);
addSuccessorWithWeight(SwitchBB, CB.FalseBB);
addSuccessorWithWeight(SwitchBB, CB.TrueBB, CB.TrueWeight);
addSuccessorWithWeight(SwitchBB, CB.FalseBB, CB.FalseWeight);
// Set NextBlock to be the MBB immediately after the current one, if any.
// This is used to avoid emitting unnecessary branches to the next block.
@@ -1910,8 +1912,8 @@ bool SelectionDAGBuilder::handleSmallSwitchRange(CaseRec& CR,
ISD::SETEQ);
// Update successor info.
SwitchBB->addSuccessor(Small.BB);
SwitchBB->addSuccessor(Default);
addSuccessorWithWeight(SwitchBB, Small.BB);
addSuccessorWithWeight(SwitchBB, Default);
// Insert the true branch.
SDValue BrCond = DAG.getNode(ISD::BRCOND, DL, MVT::Other,
@@ -1967,7 +1969,11 @@ bool SelectionDAGBuilder::handleSmallSwitchRange(CaseRec& CR,
CC = ISD::SETLE;
LHS = I->Low; MHS = SV; RHS = I->High;
}
CaseBlock CB(CC, LHS, RHS, MHS, I->BB, FallThrough, CurBlock);
uint32_t ExtraWeight = I->ExtraWeight;
CaseBlock CB(CC, LHS, RHS, MHS, /* truebb */ I->BB, /* falsebb */ FallThrough,
/* me */ CurBlock,
/* trueweight */ ExtraWeight / 2, /* falseweight */ ExtraWeight / 2);
// If emitting the first comparison, just call visitSwitchCase to emit the
// code into the current block. Otherwise, push the CaseBlock onto the
@@ -2362,12 +2368,17 @@ size_t SelectionDAGBuilder::Clusterify(CaseVector& Cases,
const SwitchInst& SI) {
size_t numCmps = 0;
BranchProbabilityInfo *BPI = FuncInfo.BPI;
// Start with "simple" cases
for (size_t i = 1; i < SI.getNumSuccessors(); ++i) {
MachineBasicBlock *SMBB = FuncInfo.MBBMap[SI.getSuccessor(i)];
BasicBlock *SuccBB = SI.getSuccessor(i);
MachineBasicBlock *SMBB = FuncInfo.MBBMap[SuccBB];
uint32_t ExtraWeight = BPI ? BPI->getEdgeWeight(SI.getParent(), SuccBB) : 0;
Cases.push_back(Case(SI.getSuccessorValue(i),
SI.getSuccessorValue(i),
SMBB));
SMBB, ExtraWeight));
}
std::sort(Cases.begin(), Cases.end(), CaseCmp());
@@ -2387,6 +2398,16 @@ size_t SelectionDAGBuilder::Clusterify(CaseVector& Cases,
if ((nextValue - currentValue == 1) && (currentBB == nextBB)) {
I->High = J->High;
J = Cases.erase(J);
if (BranchProbabilityInfo *BPI = FuncInfo.BPI) {
uint32_t CurWeight = currentBB->getBasicBlock() ?
BPI->getEdgeWeight(SI.getParent(), currentBB->getBasicBlock()) : 16;
uint32_t NextWeight = nextBB->getBasicBlock() ?
BPI->getEdgeWeight(SI.getParent(), nextBB->getBasicBlock()) : 16;
BPI->setEdgeWeight(SI.getParent(), currentBB->getBasicBlock(),
CurWeight + NextWeight);
}
} else {
I = J++;
}