[move-function-value] Make sure that we propagate the debug scope from our original debug value into new undef debug values.

Otherwise if the move is in a different scope, the backend will think that we
have two different variables and emit the corresponding dwarf.

After I have this commit in and my alloc stack hoising commit (via a different
PR), I am going to be able to commit a full end <-> end test in lldb that values
are printed out appropriately as their lifetimes begin/end.

Author: gottesmm

lib/SILOptimizer/Mandatory/MoveKillsCopyableValuesChecker.cpp

@@ -400,8 +400,8 @@ bool MoveKillsCopyableValuesChecker::check() {
     // Then look at all of our found consuming uses. See if any of these are
     // _move that are within the boundary.
     bool foundMove = false;
-    auto dbgVarInfo = DebugVarCarryingInst::getFromValue(lexicalValue);
-    StringRef varName = DebugVarCarryingInst::getName(dbgVarInfo);
+    auto dbgVarInst = DebugVarCarryingInst::getFromValue(lexicalValue);
+    StringRef varName = DebugVarCarryingInst::getName(dbgVarInst);
     for (auto *use : livenessInfo.consumingUse) {
       if (auto *mvi = dyn_cast<MoveValueInst>(use->getUser())) {
         // Only emit diagnostics if our move value allows us to.
@@ -420,14 +420,16 @@ bool MoveKillsCopyableValuesChecker::check() {
           emittedDiagnostic = true;
         } else {
           LLVM_DEBUG(llvm::dbgs() << "    WithinBoundary: No!\n");
-          if (auto varInfo = dbgVarInfo.getVarInfo()) {
-            successMovesDbgInfoCarryingInsts.push_back(*dbgVarInfo);
+          if (auto varInfo = dbgVarInst.getVarInfo()) {
+            successMovesDbgInfoCarryingInsts.push_back(*dbgVarInst);
             auto *next = mvi->getNextInstruction();
             SILBuilderWithScope builder(next);
-            // Use an autogenerated location to ensure that if we are next to a
-            // terminator, we don't assert.
+            // We need to make sure any undefs we put in are the same loc/debug
+            // scope as our original so that the backend treats them as
+            // referring to the same "debug entity".
+            builder.setCurrentDebugScope(dbgVarInst->getDebugScope());
             builder.createDebugValue(
-                dbgVarInfo.inst->getLoc(),
+                dbgVarInst->getLoc(),
                 SILUndef::get(mvi->getOperand()->getType(), mod), *varInfo,
                 false /*poison*/, true /*moved*/);
           }
@@ -439,7 +441,7 @@ bool MoveKillsCopyableValuesChecker::check() {
     // If we found a move, mark our debug var inst as having a moved value. This
     // ensures we emit llvm.dbg.addr instead of llvm.dbg.declare in IRGen.
     if (foundMove) {
-      dbgVarInfo.markAsMoved();
+      dbgVarInst.markAsMoved();
     }
   }
 

test/DebugInfo/move_function_dbginfo.swift

@@ -240,6 +240,24 @@ public func addressOnlyVarTest<T : P>(_ x: T) {
 // Conditional Tests //
 ///////////////////////
 
+// CHECK-LABEL: define swiftcc void @"$s21move_function_dbginfo23copyableValueCCFlowTestyyF"(
+// CHECK: call void @llvm.dbg.addr(metadata %T21move_function_dbginfo5KlassC** %k.debug, metadata ![[K_COPYABLE_LET_CCFLOW_METADATA:[0-9]+]], metadata !DIExpression()), !dbg ![[ADDR_LOC:[0-9]+]]
+// CHECK-NEXT: br label %[[NEXT_BB:[0-9]+]],
+//
+// CHECK: [[NEXT_BB]]:
+// CHECK:    br i1 {{%[0-9]+}}, label %[[LHS:[0-9]+]], label %[[RHS:[0-9]+]],
+//
+// CHECK: [[LHS]]:
+// CHECK:    call void @llvm.dbg.value(metadata %T21move_function_dbginfo5KlassC* undef, metadata ![[K_COPYABLE_LET_CCFLOW_METADATA]], metadata !DIExpression()), !dbg ![[ADDR_LOC]]
+public func copyableValueCCFlowTest() {
+    let k = Klass()
+    k.doSomething()
+    if trueValue {
+        let m = _move(k)
+        m.doSomething()
+    }
+}
+
 // CHECK-LABEL: define swiftcc void @"$s21move_function_dbginfo037copyableVarTestCCFlowReinitOutOfBlockF0yyF"(
 // CHECK: call void @llvm.dbg.declare(metadata %T21move_function_dbginfo5KlassC** %m.debug,
 // CHECK: call void @llvm.dbg.addr(metadata %T21move_function_dbginfo5KlassC** %k, metadata ![[K_COPYABLE_VAR_CCFLOW_REINIT_OUT_BLOCK_METADATA:[0-9]+]], metadata !DIExpression()), !dbg ![[ADDR_LOC:[0-9]*]]
@@ -385,3 +403,4 @@ public func addressOnlyVarTestCCFlowReinitInBlockTest<T : P>(_ x: T.Type) {
 // CHECK-DAG: ![[K_COPYABLE_VAR_CCFLOW_REINIT_IN_BLOCK_METADATA]] = !DILocalVariable(name: "k",
 // CHECK-DAG: ![[K_ADDRESSONLY_VAR_CCFLOW_REINIT_OUT_BLOCK_METADATA]] = !DILocalVariable(name: "k",
 // CHECK-DAG: ![[K_ADDRESSONLY_VAR_CCFLOW_REINIT_IN_BLOCK_METADATA]] = !DILocalVariable(name: "k",
+// CHECK-DAG: ![[K_COPYABLE_LET_CCFLOW_METADATA]] = !DILocalVariable(name: "k",