From 733d7cf9649968c05f41480747ed91c7b0c3a82f Mon Sep 17 00:00:00 2001
From: Chuanqi Xu <yedeng.yd@linux.alibaba.com>
Date: Tue, 24 May 2022 14:09:18 +0800
Subject: [PATCH] [Debug] [Coroutines] Add deref operator for non complex
 expression

Background:

When we construct coroutine frame, we would insert a dbg.declare
intrinsic for it:
```
%hdl = call void @llvm.coro.begin() ; would return coroutine handle
call void @llvm.dbg.declare(metadata ptr %hdl, metadata
![[DEBUG_VARIABLE: __coro_frame]], metadata !DIExpression())
```

And in the splitted coroutine, it looks like:
```
define void @coro_func.resume(ptr *hdl) {
entry.resume:
    call void @llvm.dbg.declare(metadata ptr %hdl, metadata
![[DEBUG_VARIABLE: __coro_frame]], metadata !DIExpression())
}
```

And we would salvage the debug info by inserting a new alloca here:
```
define void @coro_func.resume(ptr %hdl) {
entry.resume:
    %frame.debug = alloca ptr
    call void @llvm.dbg.declare(metadata ptr %frame.debug, metadata
![[DEBUG_VARIABLE: __coro_frame]], metadata !DIExpression())
    store ptr %hdl, %frame.debug
}
```

But now, the problem comes since the `dbg.declare` refers to the address
of that alloca instead of actual coroutine handle. I saw there are codes
to solve the problem but it only applies to complex expression only. I
feel if it is OK to relax the condition to make it work for
`__coro_frame`.

Reviewed By: jmorse

Differential Revision: https://reviews.llvm.org/D126277
---
 llvm/lib/Transforms/Coroutines/CoroFrame.cpp             | 4 ++--
 llvm/test/Transforms/Coroutines/coro-debug-coro-frame.ll | 3 ++-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/llvm/lib/Transforms/Coroutines/CoroFrame.cpp b/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
index f1caa5e98a3d..dea190901aa9 100644
--- a/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
+++ b/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
@@ -2564,6 +2564,7 @@ void coro::salvageDebugInfo(
   bool SkipOutermostLoad = !isa<DbgValueInst>(DVI);
   Value *Storage = DVI->getVariableLocationOp(0);
   Value *OriginalStorage = Storage;
+
   while (auto *Inst = dyn_cast_or_null<Instruction>(Storage)) {
     if (auto *LdInst = dyn_cast<LoadInst>(Inst)) {
       Storage = LdInst->getOperand(0);
@@ -2619,8 +2620,7 @@ void coro::salvageDebugInfo(
       // expression, we need to add a DW_OP_deref at the *start* of the
       // expression to first load the contents of the alloca before
       // adjusting it with the expression.
-      if (Expr && Expr->isComplex())
-        Expr = DIExpression::prepend(Expr, DIExpression::DerefBefore);
+      Expr = DIExpression::prepend(Expr, DIExpression::DerefBefore);
     }
 
   DVI->replaceVariableLocationOp(OriginalStorage, Storage);
diff --git a/llvm/test/Transforms/Coroutines/coro-debug-coro-frame.ll b/llvm/test/Transforms/Coroutines/coro-debug-coro-frame.ll
index 8e262c657508..f275e50cfb28 100644
--- a/llvm/test/Transforms/Coroutines/coro-debug-coro-frame.ll
+++ b/llvm/test/Transforms/Coroutines/coro-debug-coro-frame.ll
@@ -10,7 +10,8 @@
 ;
 ; CHECK:       define internal fastcc void @f.resume(
 ; CHECK:       entry.resume:
-; CHECK:            call void @llvm.dbg.declare(metadata %f.Frame** %[[FramePtr_RESUME:.*]], metadata ![[CORO_FRAME_IN_RESUME:[0-9]+]], metadata !DIExpression()
+; CHECK:            %[[FramePtr_RESUME:.*]] = alloca %f.Frame*
+; CHECK:            call void @llvm.dbg.declare(metadata %f.Frame** %[[FramePtr_RESUME]], metadata ![[CORO_FRAME_IN_RESUME:[0-9]+]], metadata !DIExpression(DW_OP_deref)
 ;
 ; CHECK-DAG: ![[FILE:[0-9]+]] = !DIFile(filename: "coro-debug.cpp"
 ; CHECK-DAG: ![[RAMP:[0-9]+]] = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov",