SILBuilder by default does not apply loc overrides for debug values, as

in the absence of a debug variable source loc, the instruction's loc
gets applied as the debug variable's loc which is incorrect. This patch
appropriately serializes the debug variable loc when possible and
reverts to the default behavior otherwise.

Also adds a test for debug_value serialization/deserialization

Author: usama54321

include/swift/SIL/SILBuilder.h

@@ -1065,7 +1065,7 @@ class SILBuilder {
       SILLocation Loc, SILValue src, SILDebugVariable Var,
       PoisonRefs_t poisonRefs = DontPoisonRefs,
       UsesMoveableValueDebugInfo_t wasMoved = DoesNotUseMoveableValueDebugInfo,
-      bool trace = false);
+      bool trace = false, bool overrideLoc = true);
   DebugValueInst *createDebugValueAddr(
       SILLocation Loc, SILValue src, SILDebugVariable Var,
       UsesMoveableValueDebugInfo_t wasMoved = DoesNotUseMoveableValueDebugInfo,

lib/SIL/IR/SILBuilder.cpp

@@ -638,17 +638,24 @@ DebugValueInst *SILBuilder::createDebugValue(SILLocation Loc, SILValue src,
                                              SILDebugVariable Var,
                                              PoisonRefs_t poisonRefs,
                                              UsesMoveableValueDebugInfo_t moved,
-                                             bool trace) {
+                                             bool trace, bool overrideLoc) {
   if (shouldDropVariable(Var, Loc))
     return nullptr;
 
   llvm::SmallString<4> Name;
 
-  // Debug location overrides cannot apply to debug value instructions.
-  DebugLocOverrideRAII LocOverride{*this, std::nullopt};
-  return insert(DebugValueInst::create(
-      getSILDebugLocation(Loc, true), src, getModule(),
-      *substituteAnonymousArgs(Name, Var, Loc), poisonRefs, moved, trace));
+  SILDebugLocation DebugLoc;
+  if (overrideLoc) {
+    // Debug location overrides cannot apply to debug value instructions.
+    DebugLocOverrideRAII LocOverride{*this, std::nullopt};
+    DebugLoc = getSILDebugLocation(Loc, true);
+  } else {
+    DebugLoc = getSILDebugLocation(Loc, true);
+  }
+
+  return insert(DebugValueInst::create(DebugLoc, src, getModule(),
+                                       *substituteAnonymousArgs(Name, Var, Loc),
+                                       poisonRefs, moved, trace));
 }
 
 DebugValueInst *SILBuilder::createDebugValueAddr(

lib/Serialization/DeserializeSIL.cpp

@@ -1628,6 +1628,7 @@ bool SILDeserializer::readSILInstruction(SILFunction *Fn,
     auto HasTrace = (Attr >> 2) & 0x1;
 
     bool HaveDebugVar = (Attr >> 3) & 0x1;
+    bool HasLoc = false;
 
     SILDebugVariable DebugVar;
     if (HaveDebugVar) {
@@ -1636,7 +1637,7 @@ bool SILDeserializer::readSILInstruction(SILFunction *Fn,
       unsigned IsDenseMapSingleton = (Attr >> 5) & 0x3;
       bool HasType = (Attr >> 7) & 0x1;
       bool HasScope = (Attr >> 8) & 0x1;
-      bool HasLoc = (Attr >> 9) & 0x1;
+      HasLoc = (Attr >> 9) & 0x1;
 
       auto VarName = MF->getIdentifierText(ListOfValues[2]);
       auto ArgNo = ListOfValues[3];
@@ -1703,8 +1704,9 @@ bool SILDeserializer::readSILInstruction(SILFunction *Fn,
       DebugVar.isDenseMapSingleton = IsDenseMapSingleton;
     }
 
-    ResultInst = Builder.createDebugValue(Loc, Value, DebugVar, PoisonRefs,
-                                          UsesMoveableValDebugInfo, HasTrace);
+    ResultInst =
+        Builder.createDebugValue(Loc, Value, DebugVar, PoisonRefs,
+                                 UsesMoveableValDebugInfo, HasTrace, !HasLoc);
 
     break;
   }

lib/Serialization/SerializeSIL.cpp

@@ -1030,6 +1030,14 @@ void SILSerializer::writeSILInstruction(const SILInstruction &SI) {
           ListOfValues.push_back(LC.first);
           ListOfValues.push_back(LC.second);
           ListOfValues.push_back(FNameID);
+        } else if (RawLoc.isFilenameAndLocation()) {
+          // TODO: this is a workaround until rdar://problem/25225083 is
+          // implemented.
+          attrs |= 1 << 9;
+          auto FNameLoc = RawLoc.getFilenameAndLocation();
+          ListOfValues.push_back(FNameLoc->line);
+          ListOfValues.push_back(FNameLoc->column);
+          ListOfValues.push_back(S.addUniquedStringRef(FNameLoc->filename));
         }
       }
 

test/Serialization/debug-value.swift

@@ -0,0 +1,33 @@
+// RUN: %empty-directory(%t)
+// RUN: %{python} %utils/split_file.py -o %t %s
+
+// RUN: %target-swift-frontend -g -experimental-serialize-debug-info -emit-module -o %t/MyModule.swiftmodule %t/MyModule.swift -O
+// RUN: %target-swift-frontend -g  -I %t %t/Main.swift -experimental-serialize-debug-info -O -emit-sil -o - | %FileCheck %s
+
+// BEGIN MyModule.swift
+@_alwaysEmitIntoClient @inline(never)
+public func bar(_ x: [Int64], sum: Int64) -> Int64 {
+    var temp = sum
+    for i in x {
+        temp += i
+    }
+    return temp
+}
+
+// BEGIN Main.swift
+import MyModule
+
+func test() {
+    let _ = bar([10], sum: 0)
+}
+// CHECK: sil {{.*}} @$s8MyModule3bar_3sums5Int64VSayAEG_AEtF : $@convention(thin) (@guaranteed Array<Int64>, Int64) -> Int64 {
+
+// CHECK: debug_value %0 : $Array<Int64>, let, name "x", argno 1, loc "{{.*}}MyModule.swift":2:19, scope
+// CHECK: debug_value %1 : $Int64, let, name "sum", argno 2, loc "{{.*}}MyModule.swift":2:31, scope
+// CHECK: [[OPERAND_ONE:%[0-9]+]] = struct_extract %1 : $Int64, #Int64._value, loc "{{.*}}MyModule.swift":3:16,
+// CHECK: debug_value [[OPERAND_ONE]] : $Builtin.Int64, var, (name "temp", loc "{{.*}}MyModule.swift":3:9, scope {{.*}}), type $Int64, expr op_fragment:#Int64._value, loc "{{.*}}MyModule.swift":3:16, scope
+// CHECK: debug_value %0 : $Array<Int64>, var, (name "$i$generator", loc "{{.*}}MyModule.swift":4:14), type $IndexingIterator<Array<Int64>>, expr op_fragment:#IndexingIterator._elements, loc "{{.*}}MyModule.swift":4:14, scope
+// CHECK: debug_value {{.*}} : $Builtin.Int64, var, (name "$i$generator", loc "{{.*}}MyModule.swift":4:14), type $IndexingIterator<Array<Int64>>, expr op_fragment:#IndexingIterator._position:op_fragment:#Int._value, loc "{{.*}}MyModule.swift":4:14, scope
+// CHECK: debug_value {{.*}} : $Builtin.Int64, var, (name "temp", loc "{{.*}}MyModule.swift":3:9, scope {{.*}}), type $Int64, expr op_fragment:#Int64._value, loc "{{.*}}MyModule.swift":5:14, scope
+
+test()