[InlineCost] Use a const reference (NFC)

[kazutakahirata]

The use of a const reference here saves 0.18% of heap allocations
during the compilation of a large preprocessed file, namely
X86ISelLowering.cpp, for the X86 target.

Note that GetTLI returns a const reference, so we don't have to worry
about a dangling reference.

[llvmbot]

@llvm/pr-subscribers-llvm-analysis

Author: Kazu Hirata (kazutakahirata)

Changes

The use of a const reference here saves 0.18% of heap allocations
during the compilation of a large preprocessed file, namely
X86ISelLowering.cpp, for the X86 target.

Note that GetTLI returns a const reference, so we don't have to worry
about a dangling reference.

---

Full diff: https://github.com/llvm/llvm-project/pull/95687.diff

1 Files Affected:

• (modified) llvm/lib/Analysis/InlineCost.cpp (+1-1)

diff --git a/llvm/lib/Analysis/InlineCost.cpp b/llvm/lib/Analysis/InlineCost.cpp
index f5b17dca49735..c3aeac7492804 100644
--- a/llvm/lib/Analysis/InlineCost.cpp
+++ b/llvm/lib/Analysis/InlineCost.cpp
@@ -2887,7 +2887,7 @@ static bool functionsHaveCompatibleAttributes(
   // caches the most recently created TLI in the TargetLibraryInfoWrapperPass
   // object, and always returns the same object (which is overwritten on each
   // GetTLI call). Therefore we copy the first result.
-  auto CalleeTLI = GetTLI(*Callee);
+  const auto &CalleeTLI = GetTLI(*Callee);
   return (IgnoreTTIInlineCompatible ||
           TTI.areInlineCompatible(Caller, Callee)) &&
          GetTLI(*Caller).areInlineCompatible(CalleeTLI,

[nikic]

See the comment directly above. The copy here is needed for the legacy pass manager. It looks like we still support AlwaysInliner for the legacy PM.

[kazutakahirata]

See the comment directly above. The copy here is needed for the legacy pass manager. It looks like we still support AlwaysInliner for the legacy PM.

Ah, thank you for pointing this out!