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Implement PR964 and Regression/CodeGen/Generic/SwitchLowering.ll

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@31119 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-10-22 21:36:53 +00:00
parent 5062250f36
commit d2c1d2200b
1 changed files with 44 additions and 5 deletions
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49
lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
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@ -889,18 +889,19 @@ void SelectionDAGLowering::visitSwitch(SwitchInst &I) {
if (++BBI != CurMBB->getParent()->end())
NextBlock = BBI;
MachineBasicBlock *Default = FuncInfo.MBBMap[I.getDefaultDest()];
// If there is only the default destination, branch to it if it is not the
// next basic block. Otherwise, just fall through.
if (I.getNumOperands() == 2) {
// Update machine-CFG edges.
MachineBasicBlock *DefaultMBB = FuncInfo.MBBMap[I.getDefaultDest()];
// If this is not a fall-through branch, emit the branch.
if (DefaultMBB != NextBlock)
if (Default != NextBlock)
DAG.setRoot(DAG.getNode(ISD::BR, MVT::Other, getRoot(),
DAG.getBasicBlock(DefaultMBB)));
DAG.getBasicBlock(Default)));
CurMBB->addSuccessor(DefaultMBB);
CurMBB->addSuccessor(Default);
return;
}
@ -920,13 +921,51 @@ void SelectionDAGLowering::visitSwitch(SwitchInst &I) {
// inserted into CaseBlock records, representing basic blocks in the binary
// search tree.
Value *SV = I.getOperand(0);
MachineBasicBlock *Default = FuncInfo.MBBMap[I.getDefaultDest()];
// Get the MachineFunction which holds the current MBB. This is used during
// emission of jump tables, and when inserting any additional MBBs necessary
// to represent the switch.
MachineFunction *CurMF = CurMBB->getParent();
const BasicBlock *LLVMBB = CurMBB->getBasicBlock();
// If the switch has few cases (two or less) emit a series of specific
// tests.
if (Cases.size() < 3) {
// TODO: If any two of the cases has the same destination, and if one value
// is the same as the other, but has one bit unset that the other has set,
// use bit manipulation to do two compares at once. For example:
// "if (X == 6 || X == 4)" -> "if ((X|2) == 6)"
// Create a CaseBlock record representing a conditional branch to
// the Case's target mbb if the value being switched on SV is equal
// to C.
MachineBasicBlock *CurBlock = CurMBB;
for (unsigned i = 0, e = Cases.size(); i != e; ++i) {
MachineBasicBlock *FallThrough;
if (i != e-1) {
FallThrough = new MachineBasicBlock(CurMBB->getBasicBlock());
CurMF->getBasicBlockList().insert(BBI, FallThrough);
} else {
// If the last case doesn't match, go to the default block.
FallThrough = Default;
}
SelectionDAGISel::CaseBlock CB(ISD::SETEQ, SV, Cases[i].first,
Cases[i].second, FallThrough, CurBlock);
// If emitting the first comparison, just call visitSwitchCase to emit the
// code into the current block. Otherwise, push the CaseBlock onto the
// vector to be later processed by SDISel, and insert the node's MBB
// before the next MBB.
if (CurBlock == CurMBB)
visitSwitchCase(CB);
else
SwitchCases.push_back(CB);
CurBlock = FallThrough;
}
return;
}
// If the switch has more than 5 blocks, and at least 31.25% dense, and the
// target supports indirect branches, then emit a jump table rather than