Clear kill flags in tail duplication.

If we duplicate an instruction then we must also clear kill flags on any uses we rewrite.
Otherwise we might be killing a register which was used in other BBs.

For example, here the entry BB ended up with these instructions, the ADD having been tail duplicated.

	%vreg24<def> = t2ADDri %vreg10<kill>, 1, pred:14, pred:%noreg, opt:%noreg; GPRnopc:%vreg24 rGPR:%vreg10
	%vreg22<def> = COPY %vreg10; GPR:%vreg22 rGPR:%vreg10

	The copy here is inserted after the add and so needs vreg10 to be live.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@236782 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 3 insertions, 0 deletions

diff --git a/lib/CodeGen/TailDuplication.cpp b/lib/CodeGen/TailDuplication.cpp
index 04b39922627..23f41c8dd4b 100644
--- a/lib/CodeGen/TailDuplication.cpp
+++ b/lib/CodeGen/TailDuplication.cpp
@@ -449,6 +449,9 @@ void TailDuplicatePass::DuplicateInstruction(MachineInstr *MI,
       DenseMap<unsigned, unsigned>::iterator VI = LocalVRMap.find(Reg);
       if (VI != LocalVRMap.end()) {
         MO.setReg(VI->second);
+        // Clear any kill flags from this operand.  The new register could have
+        // uses after this one, so kills are not valid here.
+        MO.setIsKill(false);
         MRI->constrainRegClass(VI->second, MRI->getRegClass(Reg));
       }
     }