Use human-readable scopes for adjoint buffer names

Author: asl

lib/SILOptimizer/Differentiation/PullbackCloner.cpp

@@ -564,10 +564,15 @@ class PullbackCloner::Implementation final
         bufType, loc, /*zeroInitialize*/ true,
         debugInfo.transform(
           [&](AdjointValue::DebugInfo di) {
+            llvm::raw_svector_ostream adjNameStream(adjName);
             SILDebugVariable &dv = di.second;
             dv.ArgNo = 0;
-            llvm::raw_svector_ostream(adjName) << "adjoint of '" << dv.Name
-                                               << "' in bb" << origBB->getDebugID();
+            adjNameStream << "derivative of '" << dv.Name << "'";
+            if (SILDebugLocation origBBLoc = origBB->front().getDebugLocation()) {
+              adjNameStream << " in scope at ";
+              origBBLoc.getLocation().print(adjNameStream, getASTContext().SourceMgr);
+            }
+            adjNameStream << " (scope #" << origBB->getDebugID() << ")";
             dv.Name = adjName;
             return dv;
           }));

test/AutoDiff/compiler_crashers_fixed/58660-conflicting-debug-info-inlining.swift

@@ -44,7 +44,7 @@ struct MyModel: Differentiable {
 // CHECK-LABEL: // pullback of MyModel.member4()
 // CHECK-NOT: debug_value %{{.*}} : $MyModel.TangentVector, var, name %{{.*}}, argno 1, implicit, scope
 // CHECK: bb1(%{{.*}} : $_AD__$s4main7MyModelV7member4yyF_bb1__PB__src_0_wrt_0):
-// CHECK: debug_value %{{.*}} : $MyModel.TangentVector, var, name "adjoint of 'self' in bb1", implicit, scope
+// CHECK: debug_value %{{.*}} : $MyModel.TangentVector, var, name "derivative of 'self' in scope at {{.*}} (scope #1)", implicit, scope
     // Must be a differentiable type.
     var localVar: Float = 0
 

test/AutoDiff/compiler_crashers_fixed/issue-62608-conflicting-debug-info.swift

@@ -37,8 +37,8 @@ public func pullback<T>(
 }
 
 // CHECK-LABEL: sil private @$s4main19testUpdateByCallingyyKF8fOfArrayL_5arraySdSaySdG_tFySdzcfU_TJpSUpSr :
-// CHECK: alloc_stack $Double, var, name "adjoint of 'element' in bb3"
-// CHECK: debug_value %{{.*}} : $Builtin.FPIEEE64, var, (name "adjoint of 'element' in bb1"
+// CHECK: alloc_stack $Double, var, name "derivative of 'element' in scope at {{.*}} (scope #3)"
+// CHECK: debug_value %{{.*}} : $Builtin.FPIEEE64, var, (name "derivative of 'element' in scope at {{.*}} (scope #1)"
 
 public extension Array where Element: Differentiable {
     @inlinable