[DebugInfo] Fix LoadableByAddress losing debug info

LoadableByAddress was losing debug info, including at -Onone.
When converting a load-store pair to a copy_addr, the debug info
attached to the load was not salvaged.
Additionally, the wrong scope was being attached to other debug
values.

(cherry picked from commit 644509e)

Author: Snowy1803

lib/IRGen/LoadableByAddress.cpp

@@ -33,6 +33,7 @@
 #include "swift/SILOptimizer/Analysis/DeadEndBlocksAnalysis.h"
 #include "swift/SILOptimizer/PassManager/Transforms.h"
 #include "swift/SILOptimizer/Utils/BasicBlockOptUtils.h"
+#include "swift/SILOptimizer/Utils/DebugOptUtils.h"
 #include "swift/SILOptimizer/Utils/InstOptUtils.h"
 #include "swift/SILOptimizer/Utils/StackNesting.h"
 #include "llvm/ADT/MapVector.h"
@@ -1777,7 +1778,7 @@ static void rewriteUsesOfSscalar(StructLoweringState &pass,
       createOutlinedCopyCall(copyBuilder, address, dest, pass);
       storeUser->eraseFromParent();
     } else if (auto *dbgInst = dyn_cast<DebugValueInst>(user)) {
-      SILBuilderWithScope dbgBuilder(dbgInst);
+      SILBuilder dbgBuilder(dbgInst, dbgInst->getDebugScope());
       // Rewrite the debug_value to point to the variable in the alloca.
       dbgBuilder.createDebugValueAddr(dbgInst->getLoc(), address,
                                       *dbgInst->getVarInfo());
@@ -2150,9 +2151,8 @@ static void rewriteFunction(StructLoweringState &pass,
       } else {
         assert(currOperand->getType().isAddress() &&
                "Expected an address type");
-        SILBuilderWithScope debugBuilder(instr);
         // SILBuilderWithScope skips over metainstructions.
-        debugBuilder.setCurrentDebugScope(instr->getDebugScope());
+        SILBuilder debugBuilder(instr, instr->getDebugScope());
         debugBuilder.createDebugValueAddr(instr->getLoc(), currOperand,
                                           *instr->getVarInfo());
         instr->getParent()->erase(instr);
@@ -3637,6 +3637,7 @@ class AssignAddressToDef : SILInstructionVisitor<AssignAddressToDef> {
 
     builder.createCopyAddr(load->getLoc(), load->getOperand(), addr, IsTake,
                            IsInitialization);
+    swift::salvageLoadDebugInfo(load);
     assignment.markForDeletion(load);
   }
 

test/DebugInfo/LoadableByAddress.sil

@@ -0,0 +1,49 @@
+// RUN: %target-sil-opt -loadable-address %s | %FileCheck %s
+
+sil_stage canonical
+
+import Builtin
+import Swift
+
+struct X {
+  var x1 : Int
+  var x2 : Int
+  var x3 : Int
+  var x4: Int
+  var x5: Int
+  var x6: Int
+  var x7: Int
+  var x8: Int
+  var x9: Int
+  var x10: Int
+  var x11: Int
+  var x12: Int
+  var x13: Int
+  var x14: Int
+  var x15: Int
+  var x16: Int
+}
+
+
+// CHECK: sil @test1 : $@convention(thin) () -> () {
+// CHECK: bb0:
+// CHECK:   %0 = alloc_stack $Optional<X>
+// CHECK:   %1 = alloc_stack $X
+// CHECK:   %2 = alloc_stack $X
+// CHECK:   %3 = alloc_stack $Optional<X>
+// CHECK:   debug_value %{{[0-9]+}} : $*X, let, name "temp"
+// CHECK: } // end sil function 'test1'
+
+sil @test1 : $@convention(thin) () -> () {
+bb0:
+  %0 = alloc_stack $X
+  %1 = alloc_stack $Optional<X>
+  %2 = load %0 : $*X
+  debug_value %2 : $X, let, name "temp"
+  %3 = enum $Optional<X>, #Optional.some!enumelt, %2 : $X
+  store %3 to %1 : $*Optional<X>
+  dealloc_stack %1 : $*Optional<X>
+  dealloc_stack %0 : $*X
+  %t = tuple ()
+  return %t : $()
+}