diff options
| -rw-r--r-- | llvm/lib/CodeGen/GlobalISel/RegBankSelect.cpp | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/llvm/lib/CodeGen/GlobalISel/RegBankSelect.cpp b/llvm/lib/CodeGen/GlobalISel/RegBankSelect.cpp index f417193fdeb..71687884f4d 100644 --- a/llvm/lib/CodeGen/GlobalISel/RegBankSelect.cpp +++ b/llvm/lib/CodeGen/GlobalISel/RegBankSelect.cpp @@ -10,6 +10,7 @@ /// This file implements the RegBankSelect class. //===----------------------------------------------------------------------===// +#include "llvm/ADT/PostOrderIterator.h" #include "llvm/CodeGen/GlobalISel/RegBankSelect.h" #include "llvm/CodeGen/GlobalISel/RegisterBank.h" #include "llvm/CodeGen/MachineRegisterInfo.h" @@ -125,6 +126,12 @@ void RegBankSelect::assignInstr(MachineInstr &MI) { // This will not hold when we will consider alternative mappings. DEBUG(dbgs() << "Assign: " << *ValMapping.BreakDown[0].RegBank << " to " << PrintReg(Reg) << '\n'); + // For a definition, we may be changing the register bank silently + // for all the uses here. + // Although this will be correct when we do a RPO traversal of the + // basic block, because the only uses that could be affected are + // PHIs (i.e., copies), this may not be the best solution + // according to the cost model. MRI->setRegBank(Reg, *ValMapping.BreakDown[0].RegBank); MO.setReg(Reg); } @@ -135,8 +142,11 @@ bool RegBankSelect::runOnMachineFunction(MachineFunction &MF) { DEBUG(dbgs() << "Assign register banks for: " << MF.getName() << '\n'); init(MF); // Walk the function and assign register banks to all operands. - for (MachineBasicBlock &MBB : MF) - for (MachineInstr &MI : MBB) + // Use a RPOT to make sure all registers are assigned before we choose + // the best mapping of the current instruction. + ReversePostOrderTraversal<MachineFunction*> RPOT(&MF); + for (MachineBasicBlock *MBB : RPOT) + for (MachineInstr &MI : *MBB) assignInstr(MI); return false; } |
