[MachineSink] Clear kill flags on operands outside loop

If an instruction is sunk into a loop then any kill flags on
operands declared outside the loop must be cleared as these
will be live for all loop iterations.

Fixes #46827

Reviewed By: MatzeB

Differential Revision: https://reviews.llvm.org/D126754

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/MachineSink.cpp b/llvm/lib/CodeGen/MachineSink.cpp
index 3f2330b..006ba92 100644
--- a/llvm/lib/CodeGen/MachineSink.cpp
+++ b/llvm/lib/CodeGen/MachineSink.cpp
@@ -1289,6 +1289,12 @@ bool MachineSinking::SinkIntoCycle(MachineCycle *Cycle, MachineInstr &I) {
   SinkBlock->splice(SinkBlock->SkipPHIsAndLabels(SinkBlock->begin()), Preheader,
                     I);
 
+  // Conservatively clear any kill flags on uses of sunk instruction
+  for (MachineOperand &MO : I.operands()) {
+    if (MO.isReg() && MO.readsReg())
+      RegsToClearKillFlags.insert(MO.getReg());
+  }
+
   // The instruction is moved from its basic block, so do not retain the
   // debug information.
   assert(!I.isDebugInstr() && "Should not sink debug inst");