[5.10] Fix MemoryLifetimeVerifier to ignore thin functions. #70224
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SILGen optimizes creation of closure down a thin function when it has no captures: %1 = thin_to_thick_function %0 : $@convention(thin) () -> () to $@callee_guaranteed () -> () ValueOwnership.cpp has a sketchy optimization that treat the result like a trivial type, even though it is not: > CONSTANT_OWNERSHIP_INST(None, ThinToThickFunction) commit 8c5737d Date: Fri Oct 23 15:12:18 2020 -0700 [ownership] Change thin_to_thick function to always produce a none value. This creates a mismatch between the SILType and the SILValue ownership. This is not a coherent design--we have a similar problem with enums which is endlessly buggy--but reverting the decision will be hard. Instead, I'll hack the memory verifier to silence this case. Fixes rdar://115735132 (Lifetime verifier error with opaque return type and closure) (cherry picked from commit 23ddaaf)
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Dec 5, 2023
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SILGen optimizes creation of closure down a thin function when it has no captures:
ValueOwnership.cpp has a sketchy optimization that treat the result like a trivial type, even though it is not:
This creates a mismatch between the SILType and the SILValue ownership. This is not a coherent design--we have a similar problem with enums which is endlessly buggy--but reverting the decision will be hard. Instead, I'll hack the memory verifier to silence this case.
Fixes rdar://115735132 (Lifetime verifier error with opaque return type and closure)
(cherry picked from commit 047be39)
main PR: #70223
--- CCC ---
Explanation: SILGen optimizes closures with no captures to direct calls. OSSA optimizes direct calls to have owenrship "none". This creates a mismatch between the SILType and the SILValue ownership. This causes the memory verifier to diagnose an error when the memory is not deinitialized.
Scope: This only affects the non-production (asserts) compiler. The issue was introduced three years ago.
commit 8c5737d
Date: Fri Oct 23 15:12:18 2020 -0700
[ownership] Change thin_to_thick function to always produce a none value.
Issue: rdar://115735132 (Lifetime verifier error with opaque return type and closure)
Risk: Very low. Adds a single, very specific condition which used to trigger diagnostics by the memory verifier to now be ignored.
PR to main: #70223
Testing: Added regression test to the test suite.
Reviewer: @eeckstein