Emit updated debug info when inout parameters are consumed and reinitialized.

Change SILGen to emit the `debug_value` instruction using the original inout
parameter address, instead of the `mark_must_check` inserted for move-only
parameters, because code in the MoveOnlyAddressChecker did not expect to
find the debug_value anywhere but on the original address. Update move-only
diagnostics so that they pick up the declaration name for a memory location
from any debug_value instruction if there are more than one. rdar://109740281

Author: jckarter

include/swift/SIL/DebugUtils.h

@@ -194,6 +194,16 @@ inline Operand *getSingleDebugUse(SILValue value) {
   return *ii;
 }
 
+/// If \p value has any debug user(s), return the operand associated with some
+/// use. Otherwise, returns nullptr.
+inline Operand *getAnyDebugUse(SILValue value) {
+  auto range = getDebugUses(value);
+  auto ii = range.begin(), ie = range.end();
+  if (ii == ie)
+    return nullptr;
+  return *ii;
+}
+
 /// Erases the instruction \p I from it's parent block and deletes it, including
 /// all debug instructions which use \p I.
 /// Precondition: The instruction may only have debug instructions as uses.

lib/SILGen/SILGenProlog.cpp

@@ -784,6 +784,7 @@ class ArgumentInitHelper {
       return;
     }
 
+    SILValue debugOperand = value;
     if (value->getType().isMoveOnly()) {
       switch (pd->getValueOwnership()) {
       case ValueOwnership::Default:
@@ -799,11 +800,14 @@ class ArgumentInitHelper {
                  "Should have inserted mark must check inst in EmitBBArgs");
         }
         break;
-      case ValueOwnership::InOut:
-        assert(isa<MarkMustCheckInst>(value) &&
-               "Expected mark must check inst with inout to be handled in "
-               "emitBBArgs earlier");
+      case ValueOwnership::InOut: {
+        assert(isa<MarkMustCheckInst>(value)
+               && "Expected mark must check inst with inout to be handled in "
+                  "emitBBArgs earlier");
+        auto mark = cast<MarkMustCheckInst>(value);
+        debugOperand = mark->getOperand();
         break;
+      }
       case ValueOwnership::Owned:
         value = SGF.B.createMarkMustCheckInst(
             loc, value, MarkMustCheckInst::CheckKind::ConsumableAndAssignable);
@@ -815,7 +819,17 @@ class ArgumentInitHelper {
       }
     }
 
-    SGF.B.createDebugValueAddr(loc, value, varinfo);
+    DebugValueInst *debugInst
+      = SGF.B.createDebugValueAddr(loc, debugOperand, varinfo);
+    
+    if (value != debugOperand) {
+      if (auto valueInst = dyn_cast<MarkMustCheckInst>(value)) {
+        // Move the debug instruction outside of any marker instruction that might
+        // have been applied to the value, so that analysis doesn't move the
+        // debug_value anywhere it shouldn't be.
+        debugInst->moveBefore(valueInst);
+      }
+    }
     SGF.VarLocs[pd] = SILGenFunction::VarLoc::get(value);
   }
 

lib/SILOptimizer/Mandatory/MoveOnlyAddressCheckerUtils.cpp

@@ -385,7 +385,7 @@ static bool isReinitToInitConvertibleInst(SILInstruction *memInst) {
 
 static void insertDebugValueBefore(SILInstruction *insertPt,
                                    DebugVarCarryingInst debugVar,
-                                   SILValue operand) {
+                                   llvm::function_ref<SILValue ()> operand) {
   if (!debugVar) {
     return;
   }
@@ -395,7 +395,7 @@ static void insertDebugValueBefore(SILInstruction *insertPt,
   }
   SILBuilderWithScope debugInfoBuilder(insertPt);
   debugInfoBuilder.setCurrentDebugScope(debugVar->getDebugScope());
-  debugInfoBuilder.createDebugValue(debugVar->getLoc(), operand,
+  debugInfoBuilder.createDebugValue(debugVar->getLoc(), operand(),
                                     *varInfo, false, true);
 }
 
@@ -423,7 +423,7 @@ static void convertMemoryReinitToInitForm(SILInstruction *memInst,
   // Insert a new debug_value instruction after the reinitialization, so that
   // the debugger knows that the variable is in a usable form again.
   insertDebugValueBefore(memInst->getNextInstruction(), debugVar,
-                         stripAccessMarkers(dest));
+                       [&]{ return debugVar.getOperandForDebugValueClone(); });
 }
 
 static bool memInstMustConsume(Operand *memOper) {
@@ -2333,12 +2333,10 @@ void MoveOnlyAddressCheckerPImpl::insertDestroysOnBoundary(
   // referring to the same debug variable as the original definition, we have to
   // use the same debug scope and location as the original debug var.
   auto insertUndefDebugValue = [&debugVar](SILInstruction *insertPt) {
-    if (!debugVar) {
-      return;
-    }
-    insertDebugValueBefore(insertPt, debugVar,
-      SILUndef::get(debugVar.getOperandForDebugValueClone()->getType(),
-                    insertPt->getModule()));
+    insertDebugValueBefore(insertPt, debugVar, [&]{
+      return SILUndef::get(debugVar.getOperandForDebugValueClone()->getType(),
+                           insertPt->getModule());
+    });
   };
 
   for (auto &pair : boundary.getLastUsers()) {

lib/SILOptimizer/Mandatory/MoveOnlyDiagnostics.cpp

@@ -77,7 +77,7 @@ static void getVariableNameForValue(SILValue value2,
                                     SmallString<64> &resultingString) {
   // Before we do anything, lets see if we have an exact debug_value on our
   // mmci. In such a case, we can end early and are done.
-  if (auto *use = getSingleDebugUse(value2)) {
+  if (auto *use = getAnyDebugUse(value2)) {
     if (auto debugVar = DebugVarCarryingInst(use->getUser())) {
       assert(debugVar.getKind() == DebugVarCarryingInst::Kind::DebugValue);
       resultingString += debugVar.getName();
@@ -112,7 +112,7 @@ static void getVariableNameForValue(SILValue value2,
 
     // If we do not do an exact match, see if we can find a debug_var inst. If
     // we do, we always break since we have a root value.
-    if (auto *use = getSingleDebugUse(searchValue)) {
+    if (auto *use = getAnyDebugUse(searchValue)) {
       if (auto debugVar = DebugVarCarryingInst(use->getUser())) {
         assert(debugVar.getKind() == DebugVarCarryingInst::Kind::DebugValue);
         variableNamePath.push_back(use->getUser());

test/SILOptimizer/moveonly_debug_info_reinit.swift

@@ -39,3 +39,27 @@ func bar(_ x: consuming Foo, y: consuming Foo, z: consuming Foo) {
     // CHECK: debug_value undef : $*Foo, var, name "x"
     use(&x)
 }
+
+// CHECK-LABEL: sil {{.*}} @${{.*}}10inoutParam
+func inoutParam(_ x: inout Foo, y: consuming Foo, z: consuming Foo) {
+    // CHECK: debug_value [[X:%[0-9]+]] : $*Foo, var, name "x"
+
+    // CHECK: [[USE:%.*]] = function_ref @use
+    // CHECK: apply [[USE]]
+    // CHECK: debug_value undef : $*Foo, var, name "x"
+    use(&x)
+    let _ = x
+
+    // CHECK: debug_value undef : $*Foo, var, name "y"
+    // CHECK: debug_value [[X]] : $*Foo, var, name "x"
+    x = y
+    // CHECK: [[USE:%.*]] = function_ref @use
+    // CHECK: apply [[USE]]
+    // CHECK: debug_value undef : $*Foo, var, name "x"
+    use(&x)
+    let _ = x
+
+    // CHECK: debug_value undef : $*Foo, var, name "z"
+    // CHECK: debug_value [[X]] : $*Foo, var, name "x"
+    x = z
+}