From 36cb7477d1d43de1d97a4c2b4ba0eb5ae29cbafd Mon Sep 17 00:00:00 2001
From: Alok Kumar Sharma <AlokKumar.Sharma@amd.com>
Date: Wed, 24 Nov 2021 10:38:19 +0530
Subject: [PATCH] [clang][OpenMP][DebugInfo] Debug support for private
 variables inside an OpenMP task construct

Currently variables appearing inside private/firstprivate/lastprivate
clause of openmp task construct are not visible inside lldb debugger.
This is because compiler does not generate debug info for it.

Please consider the testcase debug_private.c attached with patch.

```
   28   #pragma omp task shared(res) private(priv1, priv2) firstprivate(fpriv)
   29       {
   30         priv1 = n;
   31         priv2 = n + 2;
   32         printf("Task n=%d,priv1=%d,priv2=%d,fpriv=%d\n",n,priv1,priv2,fpriv);
   33
-> 34         res = priv1 + priv2 + fpriv + foo(n - 1);
   35       }
   36   #pragma omp taskwait
   37       return res;
(lldb) p priv1
error: <user expression 0>:1:1: use of undeclared identifier 'priv1'
priv1
^
(lldb) p priv2
error: <user expression 1>:1:1: use of undeclared identifier 'priv2'
priv2
^
(lldb) p fpriv
error: <user expression 2>:1:1: use of undeclared identifier 'fpriv'
fpriv
^
```

After the current patch, lldb is able to show the variables

```
(lldb) p priv1
(int) $0 = 10
(lldb) p priv2
(int) $1 = 12
(lldb) p fpriv
(int) $2 = 14
```

Reviewed By: djtodoro

Differential Revision: https://reviews.llvm.org/D114504
---
 clang/lib/CodeGen/CGStmtOpenMP.cpp |  3 ++
 clang/test/OpenMP/debug_private.c  | 45 ++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)
 create mode 100644 clang/test/OpenMP/debug_private.c

diff --git a/clang/lib/CodeGen/CGStmtOpenMP.cpp b/clang/lib/CodeGen/CGStmtOpenMP.cpp
index 4f14459e4d28..f6853a22cd36 100644
--- a/clang/lib/CodeGen/CGStmtOpenMP.cpp
+++ b/clang/lib/CodeGen/CGStmtOpenMP.cpp
@@ -4510,6 +4510,9 @@ void CodeGenFunction::EmitOMPTaskBasedDirective(
         Address Replacement(CGF.Builder.CreateLoad(Pair.second),
                             CGF.getContext().getDeclAlign(Pair.first));
         Scope.addPrivate(Pair.first, [Replacement]() { return Replacement; });
+        if (auto *DI = CGF.getDebugInfo())
+          DI->EmitDeclareOfAutoVariable(Pair.first, Pair.second.getPointer(),
+                                        CGF.Builder, /*UsePointerValue*/ true);
       }
       // Adjust mapping for internal locals by mapping actual memory instead of
       // a pointer to this memory.
diff --git a/clang/test/OpenMP/debug_private.c b/clang/test/OpenMP/debug_private.c
new file mode 100644
index 000000000000..a68e1d1be752
--- /dev/null
+++ b/clang/test/OpenMP/debug_private.c
@@ -0,0 +1,45 @@
+// This testcase checks emission of debug info for variables inside
+// private/firstprivate/lastprivate.
+
+// REQUIRES: x86_64-linux
+
+// RUN: %clang_cc1 -debug-info-kind=constructor -x c -verify -triple x86_64-pc-linux-gnu -fopenmp -emit-llvm %s -o - | FileCheck %s
+// expected-no-diagnostics
+
+// CHECK: define internal i32 @.omp_task_entry.
+
+// CHECK:  call void @llvm.dbg.declare(metadata i32** %.priv.ptr.addr.i, metadata [[PRIV1:![0-9]+]], metadata !DIExpression(DW_OP_deref))
+// CHECK:  call void @llvm.dbg.declare(metadata i32** %.priv.ptr.addr1.i, metadata [[PRIV2:![0-9]+]], metadata !DIExpression(DW_OP_deref))
+// CHECK:  call void @llvm.dbg.declare(metadata i32** %.firstpriv.ptr.addr.i, metadata [[FPRIV:![0-9]+]], metadata !DIExpression(DW_OP_deref))
+
+// CHECK: [[PRIV1]] = !DILocalVariable(name: "priv1"
+// CHECK: [[PRIV2]] = !DILocalVariable(name: "priv2"
+// CHECK: [[FPRIV]] = !DILocalVariable(name: "fpriv"
+
+extern int printf(const char *, ...);
+
+int foo(int n) {
+  int res, priv1, priv2, fpriv;
+  fpriv = n + 4;
+
+  if (n < 2)
+    return n;
+  else {
+#pragma omp task shared(res) private(priv1, priv2) firstprivate(fpriv)
+    {
+      priv1 = n;
+      priv2 = n + 2;
+      printf("Task n=%d,priv1=%d,priv2=%d,fpriv=%d\n", n, priv1, priv2, fpriv);
+
+      res = priv1 + priv2 + fpriv + foo(n - 1);
+    }
+#pragma omp taskwait
+    return res;
+  }
+}
+
+int main() {
+  int n = 10;
+  printf("foo(%d) = %d\n", n, foo(n));
+  return 0;
+}