diff options
Diffstat (limited to 'lib/CodeGen/TwoAddressInstructionPass.cpp')
| -rw-r--r-- | lib/CodeGen/TwoAddressInstructionPass.cpp | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/lib/CodeGen/TwoAddressInstructionPass.cpp b/lib/CodeGen/TwoAddressInstructionPass.cpp index dc6b3420ab..8002ff2c64 100644 --- a/lib/CodeGen/TwoAddressInstructionPass.cpp +++ b/lib/CodeGen/TwoAddressInstructionPass.cpp @@ -1728,8 +1728,10 @@ TwoAddressInstructionPass::CoalesceExtSubRegs(SmallVector<unsigned,4> &Srcs, CanCoalesce = false; break; } - // Keep track of one of the uses. - SomeMI = UseMI; + // Keep track of one of the uses. Preferably the first one which has a + // <def,undef> flag. + if (!SomeMI || UseMI->getOperand(0).isUndef()) + SomeMI = UseMI; } if (!CanCoalesce) continue; @@ -1738,7 +1740,9 @@ TwoAddressInstructionPass::CoalesceExtSubRegs(SmallVector<unsigned,4> &Srcs, MachineInstr *CopyMI = BuildMI(*SomeMI->getParent(), SomeMI, SomeMI->getDebugLoc(), TII->get(TargetOpcode::COPY)) - .addReg(DstReg, RegState::Define, NewDstSubIdx) + .addReg(DstReg, RegState::Define | + getUndefRegState(SomeMI->getOperand(0).isUndef()), + NewDstSubIdx) .addReg(SrcReg, 0, NewSrcSubIdx); // Remove all the old extract instructions. |