[llvm] 0ae989a - Pass DebugLoc::appendInlinedAt DebugLoc arg by const reference not value.

[Robinson, Paul via llvm-commits]

> -----Original Message-----
> From: llvm-commits <llvm-commits-bounces at lists.llvm.org> On Behalf Of
> Simon Pilgrim via llvm-commits
> Sent: Wednesday, July 1, 2020 11:39 AM
> To: llvm-commits at lists.llvm.org
> Subject: [llvm] 0ae989a - Pass DebugLoc::appendInlinedAt DebugLoc arg by
> const reference not value.
> 
> 
> Author: Simon Pilgrim
> Date: 2020-07-01T16:38:51+01:00
> New Revision: 0ae989a1fede0e512e2bfd57b328aad6c1920329
> 
> URL: https://github.com/llvm/llvm-
> project/commit/0ae989a1fede0e512e2bfd57b328aad6c1920329
> DIFF: https://github.com/llvm/llvm-
> project/commit/0ae989a1fede0e512e2bfd57b328aad6c1920329.diff
> 
> LOG: Pass DebugLoc::appendInlinedAt DebugLoc arg by const reference not
> value.
> 
> Noticed by clang-tidy performance-unnecessary-value-param warning.

Is it really a performance thing?  Somehow I had it in my head that
DebugLoc was deliberately lightweight to make it easy to pass by value;
perhaps I'm thinking of something else, as I don't see a comment to 
that effect in DebugLoc.h, but still it doesn't look that heavy.
--paulr

> 
> Added:
> 
> 
> Modified:
>     llvm/include/llvm/IR/DebugLoc.h
>     llvm/lib/IR/DebugLoc.cpp
> 
> Removed:
> 
> 
> 
> ##########################################################################
> ######
> diff  --git a/llvm/include/llvm/IR/DebugLoc.h
> b/llvm/include/llvm/IR/DebugLoc.h
> index 780d17a33661..4914d733fe0d 100644
> --- a/llvm/include/llvm/IR/DebugLoc.h
> +++ b/llvm/include/llvm/IR/DebugLoc.h
> @@ -85,7 +85,7 @@ namespace llvm {
>      /// the chain now is inlined-at the new call site.
>      /// \param   InlinedAt    The new outermost inlined-at in the chain.
>      /// \param   ReplaceLast  Replace the last location in the inlined-at
> chain.
> -    static DebugLoc appendInlinedAt(DebugLoc DL, DILocation *InlinedAt,
> +    static DebugLoc appendInlinedAt(const DebugLoc &DL, DILocation
> *InlinedAt,
>                                      LLVMContext &Ctx,
>                                      DenseMap<const MDNode *, MDNode *>
> &Cache,
>                                      bool ReplaceLast = false);
> 
> diff  --git a/llvm/lib/IR/DebugLoc.cpp b/llvm/lib/IR/DebugLoc.cpp
> index 14d1396f1543..e945cbcba782 100644
> --- a/llvm/lib/IR/DebugLoc.cpp
> +++ b/llvm/lib/IR/DebugLoc.cpp
> @@ -79,7 +79,7 @@ DebugLoc DebugLoc::get(unsigned Line, unsigned Col,
> const MDNode *Scope,
>                           const_cast<MDNode *>(InlinedAt), ImplicitCode);
>  }
> 
> -DebugLoc DebugLoc::appendInlinedAt(DebugLoc DL, DILocation *InlinedAt,
> +DebugLoc DebugLoc::appendInlinedAt(const DebugLoc &DL, DILocation
> *InlinedAt,
>                                     LLVMContext &Ctx,
>                                     DenseMap<const MDNode *, MDNode *>
> &Cache,
>                                     bool ReplaceLast) {
> 
> 
> 
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