MemcpyOpt doesn't strip TBAA correctly

[gbaraldi]

While debugging JuliaLang/julia#57959. It got minimized to what looks to be a bug in MemCpyOpt, where it strips the noalias attribute of a memcpy

llvm-project/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp

Lines 1682 to 1688 in 3c7a0e6

	// As this transformation can cause memory accesses that didn't previously
	// alias to begin to alias one another, we remove !noalias metadata from any
	// uses of either alloca. This is conservative, but more precision doesn't
	// seem worthwhile right now.
	for (Instruction *I : NoAliasInstrs)
	I->setMetadata(LLVMContext::MD_noalias, nullptr);

but not the other aliasing metadatas (tbaa,tbaa.struct). Probably using combineMetadata as used elsewhere in the pass
@khei4 was the one that originally added this optimization

[gbaraldi]

https://godbolt.org/z/qv1Mqo7eP For a small reproducer

[nikic]

There is a related PR here: #129537

[nikic]

/cherry-pick 716b02d

[llvmbot]

Failed to cherry-pick: 716b02d

https://github.com/llvm/llvm-project/actions/runs/14404185715

Please manually backport the fix and push it to your github fork. Once this is done, please create a pull request

[tstellar]

@nikic Were you able to manually backport this one?