[SYCL][ESIMD] Fix leak of the demangler output buffer

[uditagarwal97]

Problem

SYCLLowerESIMDPass::prepareForAlwaysInliner() demangles each function name to decide whether it belongs to the ESIMD namespaces:

id::OutputBuffer NameBuf;
NameNode->print(NameBuf);
StringRef Name(NameBuf.getBuffer(), NameBuf.getCurrentPosition());

return Name.starts_with("sycl::_V1::ext::intel::esimd::") ||
       Name.starts_with("sycl::_V1::ext::intel::experimental::esimd::");

llvm::itanium_demangle::OutputBuffer grows its storage with realloc and has a defaulted destructor — it does not own that storage, and the caller is required to std::free(getBuffer()). This lambda is invoked once per function in the module and leaks the buffer every time.

LeakSanitizer report (ASan+UBSan build, leak reached through clang++ -fsycl on an ESIMD test):

Direct leak of 998 byte(s) in 1 object(s) allocated from:
    #0 ... in realloc
    #1 ... in llvm::itanium_demangle::OutputBuffer::grow(unsigned long)
    #2 ... in SYCLLowerESIMDPass::prepareForAlwaysInliner(llvm::Module&)
    llvm/lib/SYCLLowerIR/ESIMD/LowerESIMD.cpp:1985

Observed 998 B to ~14 KB per compilation depending on how many ESIMD functions the module contains.

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Co-Authored-By: Claude Opus 5 (1M context) noreply@anthropic.com

[Copilot]

🟢 Approval recommended

The cleanup follows OutputBuffer’s ownership contract without changing pass behavior.

Pull request overview

Fixes a per-function demangling buffer leak in ESIMD lowering.

Changes:

• Adds <cstdlib> for std::free.
• Frees the demangled-name buffer after namespace checks.

File summaries

File	Description
llvm/lib/SYCLLowerIR/ESIMD/LowerESIMD.cpp	Releases OutputBuffer storage before returning.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 0
• Review effort level: Balanced

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