[all-commits] [llvm/llvm-project] 2e5a52: [flang][debug] Avoid redundant debug data generati...

[Abid Qadeer via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 2e5a5237daf82a657561c490845c406e13657311
      https://github.com/llvm/llvm-project/commit/2e5a5237daf82a657561c490845c406e13657311
  Author: Abid Qadeer <haqadeer at amd.com>
  Date:   2025-01-27 (Mon, 27 Jan 2025)

  Changed paths:
    M flang/lib/Optimizer/Transforms/DebugTypeGenerator.cpp
    M flang/lib/Optimizer/Transforms/DebugTypeGenerator.h
    M flang/test/Integration/debug-cyclic-derived-type-3.f90

  Log Message:
  -----------
  [flang][debug] Avoid redundant debug data generation for derived types. (#124473)

Since https://github.com/llvm/llvm-project/pull/122770, we have seen
that compile time have become extremely slow for cyclic derived types.
In #122770, we made the criteria to cache a derived type very strict. As
a result, some types which are safe to cache were also being
re-generated every type they were required. This increased the compile
time and also the size of the debug info.

Please see the description of PR# 122770. We decided that when
processing `t1`, the type generated for `t2` and `t3` were not safe to
cached. But our algorithm also denied caching to `t1` which as top level
type was safe.

```
type t1
  type(t2), pointer :: p1
end type
type t2
  type(t3), pointer :: p2
end type
type t3
  type(t1), pointer :: p3
end type
```

I have tinkered the check a bit so that top level type is always cached.
To detect a top level type, we use a depth counter that get incremented
before call to `convertRecordType` and decremented after it returns.

After this change, the following
[file](https://github.com/fujitsu/compiler-test-suite/blob/main/Fortran/0394/0394_0031.f90)
from Fujitsu get compiled around 40s which is same as it was before
#122770.


The smaller testcase present in issue #124049 takes less than half a
second. I also added check to make sure that duplicate entries of the
`DICompositeType` are not present in the IR.

Fixes #124049 and #123960.



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