Allow missing kill flags on an untied operand of a two-address instruction when

the operand uses the same register as a tied operand:

  %r1 = add %r1, %r1

If add were a three-address instruction, kill flags would be required on at
least one of the uses. Since it is a two-address instruction, the tied use
operand must not have a kill flag.

This change makes the kill flag on the untied use operand optional.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122082 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 6 insertions, 1 deletions

diff --git a/lib/CodeGen/MachineVerifier.cpp b/lib/CodeGen/MachineVerifier.cpp
index f92b7fe5ac..1e2b478e93 100644
--- a/lib/CodeGen/MachineVerifier.cpp
+++ b/lib/CodeGen/MachineVerifier.cpp
@@ -625,7 +625,12 @@ MachineVerifier::visitMachineOperand(const MachineOperand *MO, unsigned MONum) {
             *OS << UseIdx << " is not live in " << LI << '\n';
           }
           // Verify isKill == LI.killedAt.
-          if (!MI->isRegTiedToDefOperand(MONum)) {
+          // Two-address instrs don't have kill flags on the tied operands, and
+          // we even allow
+          //   %r1 = add %r1, %r1
+          // without a kill flag on the untied operand.
+          // MI->findRegisterUseOperandIdx finds the first operand using reg.
+          if (!MI->isRegTiedToDefOperand(MI->findRegisterUseOperandIdx(Reg))) {
             // MI could kill register without a kill flag on MO.
             bool miKill = MI->killsRegister(Reg);
             bool liKill = LI.killedAt(UseIdx.getDefIndex());