Fix IRGen debug info for swift_task_alloc'ed variables.

The old code attempted to load the variable despite not knowing its size. Fixed
by describing the variable's address on the task heap.

Author: adrian-prantl

lib/IRGen/IRGenSIL.cpp

@@ -5390,8 +5390,11 @@ void IRGenSILFunction::emitDebugInfoForAllocStack(AllocStackInst *i,
   assert(isa<llvm::AllocaInst>(addr) || isa<llvm::UndefValue>(addr) ||
          isa<llvm::IntrinsicInst>(addr) || isCallToSwiftTaskAlloc(addr));
 
-  auto Indirection =
-      InCoroContext(*CurSILFn, *i) ? CoroDirectValue : DirectValue;
+  auto Indirection = DirectValue;
+  if (InCoroContext(*CurSILFn, *i))
+    Indirection =
+        isCallToSwiftTaskAlloc(addr) ? CoroIndirectValue : CoroDirectValue;
+
   if (!IGM.IRGen.Opts.DisableDebuggerShadowCopies &&
       !IGM.IRGen.Opts.shouldOptimize())
     if (auto *Alloca = dyn_cast<llvm::AllocaInst>(addr))
@@ -5435,25 +5438,6 @@ void IRGenSILFunction::emitDebugInfoForAllocStack(AllocStackInst *i,
   } else
     return;
 
-  // Async functions use the value of the artificial address.
-  auto shadow = addr;
-  if (CurSILFn->isAsync() && emitLifetimeExtendingUse(shadow) &&
-      !isa<llvm::UndefValue>(shadow)) {
-    if (ValueVariables.insert(shadow).second)
-      ValueDomPoints.push_back({shadow, getActiveDominancePoint()});
-    auto shadowInst = cast<llvm::Instruction>(shadow);
-    llvm::IRBuilder<> builder(shadowInst->getNextNode());
-    llvm::Type *shadowTy = IGM.IntPtrTy;
-    if (auto *alloca = dyn_cast<llvm::AllocaInst>(shadow)) {
-      shadowTy = alloca->getAllocatedType();
-    } else if (isCallToSwiftTaskAlloc(shadow)) {
-      shadowTy = IGM.Int8Ty;
-    }
-    assert(!IGM.getLLVMContext().supportsTypedPointers() ||
-           shadowTy == shadow->getType()->getNonOpaquePointerElementType());
-    addr = builder.CreateLoad(shadowTy, shadow);
-  }
-
   bindArchetypes(DbgTy.getType());
   if (IGM.DebugInfo) {
     emitDebugVariableDeclaration(addr, DbgTy, SILTy, DS, i->getLoc(), *VarInfo,

test/DebugInfo/async-lifetime-extension.swift

@@ -8,8 +8,8 @@
 
 // CHECK-LABEL: define {{.*}} void @"$s1a4fiboyS2iYaFTY0_"
 // CHECK-NEXT: entryresume.0:
-// CHECK-NEXT: call void @llvm.dbg.declare(metadata {{.*}}%0, metadata ![[R:[0-9]+]], {{.*}}!DIExpression(DW_OP
 // CHECK-NEXT: call void @llvm.dbg.declare(metadata {{.*}}%0, metadata ![[N:[0-9]+]], {{.*}}!DIExpression(DW_OP
+// CHECK-NEXT: call void @llvm.dbg.declare(metadata {{.*}}%0, metadata ![[R:[0-9]+]], {{.*}}!DIExpression(DW_OP
 // CHECK-NEXT: call void @llvm.dbg.declare(metadata {{.*}}%0, metadata ![[LHS:[0-9]+]], {{.*}}!DIExpression(DW_OP
 // CHECK-NEXT: call void @llvm.dbg.declare(metadata {{.*}}%0, metadata ![[RHS:[0-9]+]], {{.*}}!DIExpression(DW_OP
 // CHECK-NOT: {{ ret }}

test/DebugInfo/async-task-alloc.swift

@@ -0,0 +1,20 @@
+// RUN: %target-swift-frontend %s -emit-ir -g -o - \
+// RUN:    -module-name a  -disable-availability-checking \
+// RUN:    | %FileCheck %s --check-prefix=CHECK
+// REQUIRES: concurrency
+
+// Test dynamically allocated local variables in async functions.
+
+// CHECK-LABEL: define {{.*}} void @"$s1a1fyxxYalF"
+// CHECK: swift_task_alloc
+// CHECK-LABEL: define {{.*}} void @"$s1a1fyxxYalFTY0_"
+// CHECK-NEXT: entryresume.0:
+// CHECK-NEXT: call void @llvm.dbg.declare(metadata {{.*}}%0, metadata ![[T:[0-9]+]], {{.*}}!DIExpression({{.*}}DW_OP_deref
+// CHECK-NEXT: call void @llvm.dbg.declare(metadata {{.*}}%0, metadata ![[DYNA:[0-9]+]], {{.*}}!DIExpression({{.*}}DW_OP_deref
+
+// CHECK: ![[DYNA]] = !DILocalVariable(name: "dyna"
+// CHECK: ![[T]] = !DILocalVariable(name: "t"
+public func f<T>(_ t: T) async -> T {
+  let dyna = t
+  return dyna
+}