[RegBankSelect] Add a method to avoid splitting while repairing.

The previous choice of the insertion points for repairing was
straightfoward but may introduce some basic block or edge splitting. In
some situation this is something we can avoid.
For instance, when repairing a phi argument, instead of placing the
repairing on the related incoming edge, we may move it to the previous
block, before the terminators. This is only possible when the argument
is not defined by one of the terminator.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@270232 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 0 deletions

diff --git a/include/llvm/CodeGen/GlobalISel/RegBankSelect.h b/include/llvm/CodeGen/GlobalISel/RegBankSelect.h
index 028fe95d80c..d329d529246 100644
--- a/include/llvm/CodeGen/GlobalISel/RegBankSelect.h
+++ b/include/llvm/CodeGen/GlobalISel/RegBankSelect.h
@@ -515,6 +515,18 @@ private:
                  const RegisterBankInfo::InstructionMapping &InstrMapping,
                  SmallVectorImpl<RepairingPlacement> &RepairPts);
 
+  /// When \p RepairPt involves splitting to repair \p MO for the
+  /// given \p ValMapping, try to change the way we repair such that
+  /// the splitting is not required anymore.
+  ///
+  /// \pre \p RepairPt.hasSplit()
+  /// \pre \p MO == MO.getParent()->getOperand(\p RepairPt.getOpIdx())
+  /// \pre \p ValMapping is the mapping of \p MO for MO.getParent()
+  ///      that implied \p RepairPt.
+  void tryAvoidingSplit(RegBankSelect::RepairingPlacement &RepairPt,
+                        const MachineOperand &MO,
+                        const RegisterBankInfo::ValueMapping &ValMapping) const;
+
   /// Apply \p Mapping to \p MI. \p RepairPts represents the different
   /// mapping action that need to happen for the mapping to be
   /// applied.