Allow machine dce to remove uses in the same instruction
Machine DCE cannot remove a dead definition if there are non-dbg uses.
A use however can be in the same instruction:
dead %0 = INST %0
Such instructions sometimes created by Detect dead lanes pass.
Allow this instruction to be deleted despite the use if the only use
belongs to the same instruction.
Differential Revision: https://reviews.llvm.org/D59565
llvm-svn: 356619
diff --git a/llvm/lib/CodeGen/DeadMachineInstructionElim.cpp b/llvm/lib/CodeGen/DeadMachineInstructionElim.cpp
index 36c7de6..049ce70 100644
--- a/llvm/lib/CodeGen/DeadMachineInstructionElim.cpp
+++ b/llvm/lib/CodeGen/DeadMachineInstructionElim.cpp
@@ -81,9 +81,11 @@
if (LivePhysRegs.test(Reg) || MRI->isReserved(Reg))
return false;
} else {
- if (!MRI->use_nodbg_empty(Reg))
- // This def has a non-debug use. Don't delete the instruction!
- return false;
+ for (const MachineInstr &Use : MRI->use_nodbg_instructions(Reg)) {
+ if (&Use != MI)
+ // This def has a non-debug use. Don't delete the instruction!
+ return false;
+ }
}
}
}