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SelectionDAGISel can now natively handle Switch instructions, in the same

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manner that the LowerSwitch LLVM to LLVM pass does: emitting a binary
search tree of basic blocks.  The new approach has several advantages:
it is faster, it generates significantly smaller code in many cases, and
it paves the way for implementing dense switch tables as a jump table by
handling switches directly in the instruction selector.

This functionality is currently only enabled on x86, but should be safe for
every target.  In anticipation of making it the default, the cfg is now
properly updated in the x86, ppc, and sparc select lowering code.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@27156 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nate Begeman
2006-03-27 01:32:24 +00:00
parent fbcf23c3c1
commit f15485a8d0
6 changed files with 334 additions and 45 deletions
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10
lib/Target/PowerPC/PPCISelLowering.cpp
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@@ -1260,7 +1260,15 @@ PPCTargetLowering::InsertAtEndOfBasicBlock(MachineInstr *MI,
MachineFunction *F = BB->getParent();
F->getBasicBlockList().insert(It, copy0MBB);
F->getBasicBlockList().insert(It, sinkMBB);
// Update machine-CFG edges
// Update machine-CFG edges by first adding all successors of the current
// block to the new block which will contain the Phi node for the select.
for(MachineBasicBlock::succ_iterator i = BB->succ_begin(),
e = BB->succ_end(); i != e; ++i)
sinkMBB->addSuccessor(*i);
// Next, remove all successors of the current block, and add the true
// and fallthrough blocks as its successors.
while(!BB->succ_empty())
BB->removeSuccessor(BB->succ_begin());
BB->addSuccessor(copy0MBB);
BB->addSuccessor(sinkMBB);