Let MachineVerifier be aware of mem-to-mem instructions.

A mem-to-mem instruction (that both loads and stores), which store to an
FI, cannot pass the verifier since it thinks it is loading from the FI.

For the mem-to-mem instruction, do a looser check in visitMachineOperand()
and only check liveness at the reg-slot while analyzing a frame index operand.

Needed to make CodeGen/SystemZ/xor-01.ll pass with -verify-machineinstrs,
which now runs with this flag.

Reviewed by Evan Cheng and Quentin Colombet.

llvm-svn: 250885

1 files changed, 8 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/MachineVerifier.cpp b/llvm/lib/CodeGen/MachineVerifier.cpp
index c21b875a082..b9ca0c51d76 100644
--- a/llvm/lib/CodeGen/MachineVerifier.cpp
+++ b/llvm/lib/CodeGen/MachineVerifier.cpp
@@ -994,11 +994,17 @@ MachineVerifier::visitMachineOperand(const MachineOperand *MO, unsigned MONum) {
         LiveInts && !LiveInts->isNotInMIMap(MI)) {
       LiveInterval &LI = LiveStks->getInterval(MO->getIndex());
       SlotIndex Idx = LiveInts->getInstructionIndex(MI);
-      if (MI->mayLoad() && !LI.liveAt(Idx.getRegSlot(true))) {
+
+      // For a memory-to-memory move, we don't know if MI is using
+      // this frame index for loading or storing, so check for
+      // liveness at reg-slot only in the simple load case.
+      bool stores = MI->mayStore();
+      bool simpleLoad = (MI->mayLoad() && !stores);
+      if (simpleLoad && !LI.liveAt(Idx.getRegSlot(true))) {
         report("Instruction loads from dead spill slot", MO, MONum);
         errs() << "Live stack: " << LI << '\n';
       }
-      if (MI->mayStore() && !LI.liveAt(Idx.getRegSlot())) {
+      if (stores && !LI.liveAt(Idx.getRegSlot())) {
         report("Instruction stores to dead spill slot", MO, MONum);
         errs() << "Live stack: " << LI << '\n';
       }