[GlobalISel] Emit DBG_VALUE %noreg for non-int/fp constant values.

When a dbg_value has a constant operand that isn't representable in MI,
there isn't much we can do.  Use %noreg (0) for those situations.
This matches the SelectionDAG behavior.

llvm-svn: 297200

1 files changed, 6 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
index 3614333037c..8630ef842b4 100644
--- a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
@@ -137,8 +137,13 @@ MachineInstrBuilder MachineIRBuilder::buildConstDbgValue(const Constant &C,
       MIB.addCImm(CI);
     else
       MIB.addImm(CI->getZExtValue());
-  } else
+  } else if (auto *CFP = dyn_cast<ConstantFP>(&C)) {
+    assert(isa<ConstantFP>(C) && "Unexpected constant dbg value");
     MIB.addFPImm(&cast<ConstantFP>(C));
+  } else {
+    // Insert %noreg if we didn't find a usable constant and had to drop it.
+    MIB.addReg(0U);
+  }
 
   return MIB.addImm(Offset).addMetadata(Variable).addMetadata(Expr);
 }