[LiveDebugValues] Terminate open ranges on DBG_VALUE $noreg

In D68209, LiveDebugValues::transferDebugValue had a call to
OpenRanges.erase shifted, and by accident this led to a code path where
DBG_VALUEs of $noreg would not have their open range terminated, allowing
variable locations to extend past blocks where they were terminated.

This patch correctly terminates the open range, if present, when such a
DBG_VAUE is encountered, and adds a test for this behaviour.

Differential Revision: https://reviews.llvm.org/D78218

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/LiveDebugValues.cpp b/llvm/lib/CodeGen/LiveDebugValues.cpp
index 530da52..fdea702 100644
--- a/llvm/lib/CodeGen/LiveDebugValues.cpp
+++ b/llvm/lib/CodeGen/LiveDebugValues.cpp
@@ -968,9 +968,11 @@ void LiveDebugValues::transferDebugValue(const MachineInstr &MI,
   } else if (MI.hasOneMemOperand()) {
     llvm_unreachable("DBG_VALUE with mem operand encountered after regalloc?");
   } else {
-    // This must be an undefined location. We should leave OpenRanges closed.
+    // This must be an undefined location. If it has an open range, erase it.
     assert(MI.getOperand(0).isReg() && MI.getOperand(0).getReg() == 0 &&
            "Unexpected non-undef DBG_VALUE encountered");
+    VarLoc VL(MI, LS);
+    OpenRanges.erase(VL);
   }
 }