forked from OSchip/llvm-project
eb46641c28
Arguments to function calls marked "nocapture" can be marked as non-escaping. However, nocapture is defined in terms of the lifetime of the callee, and if the callee can directly or indirectly recurse to the caller, the semantics of nocapture are invalid. Therefore, we eagerly discover which SCC each function belongs to, and later can check if callee and caller of a callsite belong to the same SCC, in which case there could be recursion. This means that we can't be so optimistic in getModRefInfo(ImmutableCallsite) - previously we assumed all call arguments never aliased with an escaping global. Now we need to check, because a global could now be passed as an argument but still not escape. This also solves a related conformance problem: MemCpyOptimizer can turn non-escaping stores of globals into calls to intrinsics like llvm.memcpy/llvm/memset. This confuses GlobalsAA, which knows the global can't escape and so returns NoModRef when queried, when obviously a memcpy/memset call does indeed reference and modify its arguments. This fixes PR24800, PR24801, and PR24802. llvm-svn: 248576 |
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