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Describe tail merging's use of InsertBranch.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@65062 91177308-0d34-0410-b5e6-96231b3b80d8
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Dale Johannesen 2009-02-19 19:40:21 +00:00
parent 4a359ea2d5
commit c1c9d7e6a9
1 changed files with 11 additions and 6 deletions
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17
include/llvm/Target/TargetInstrInfo.h
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@ -182,15 +182,15 @@ public:
/// 2. If this block ends with only an unconditional branch, it sets TBB to be
/// the destination block.
/// 3. If this block ends with an conditional branch and it falls through to
/// an successor block, it sets TBB to be the branch destination block and a
/// list of operands that evaluate the condition. These
/// an successor block, it sets TBB to be the branch destination block and
/// a list of operands that evaluate the condition. These
/// operands can be passed to other TargetInstrInfo methods to create new
/// branches.
/// 4. If this block ends with an conditional branch and an unconditional
/// block, it returns the 'true' destination in TBB, the 'false' destination
/// in FBB, and a list of operands that evaluate the condition. These
/// operands can be passed to other TargetInstrInfo methods to create new
/// branches.
/// block, it returns the 'true' destination in TBB, the 'false'
/// destination in FBB, and a list of operands that evaluate the condition.
/// These operands can be passed to other TargetInstrInfo methods to create
/// new branches.
///
/// Note that RemoveBranch and InsertBranch must be implemented to support
/// cases where this method returns success.
@ -219,6 +219,11 @@ public:
/// returns success and when an unconditional branch (TBB is non-null, FBB is
/// null, Cond is empty) needs to be inserted. It returns the number of
/// instructions inserted.
///
/// It is also invoked by tail merging to add unconditional branches in
/// cases where AnalyzeBranch doesn't apply because there was no original
/// branch to analyze. At least this much must be implemented, else tail
/// merging needs to be disabled.
virtual unsigned InsertBranch(MachineBasicBlock &MBB, MachineBasicBlock *TBB,
MachineBasicBlock *FBB,
const SmallVectorImpl<MachineOperand> &Cond) const {