SILGen: revise emission of UnreachableExpr #84779
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The prior emission strategy produced some scary SIL where we have a copy of uninitialized memory: ``` ignored_use %14 %16 = alloc_stack $T unreachable bb1: copy_addr [take] %16 to [init] %0 dealloc_stack %16 ``` I assume this was done to dodge the SILVerifier, which will catch a take of an uninitialized address, had the alloc_stack been in any reachable predecessor. We already have a representation for an undefined value in SIL, so I'd rather use that than try to sneak one past the verifier. This adjusted emission also is opaque values friendly, as it doesn't assume the result value is an address. resolves rdar://162239557
kavon force-pushed the opaque-values/unreachable-expr-rdar162239557 branch from 1cbeb9f to 1e28b0a Compare | @swift-ci smoke test |
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The prior emission strategy produced some scary SIL where we have a copy of uninitialized memory:
I assume this was done to dodge the SILVerifier, which will catch a take of an uninitialized address, had the alloc_stack been in any reachable predecessor.
We already have a representation for an undefined value in SIL, so I'd rather use that than try to sneak one past the verifier.
This adjusted emission also is opaque values friendly, as it doesn't assume the result value is an address.
resolves rdar://162239557