Juneyoung Lee c70101b156 Allow nonnull/align attribute to accept poison ... Currently LLVM is relying on ValueTracking's `isKnownNonZero` to attach `nonnull`, which can return true when the value is poison. To make the semantics of `nonnull` consistent with the behavior of `isKnownNonZero`, this makes the semantics of `nonnull` to accept poison, and return poison if the input pointer isn't null. This makes many transformations like below legal: ``` %p = gep inbounds %x, 1 ; % p is non-null pointer or poison call void @f(%p) ; instcombine converts this to call void @f(nonnull %p) ``` Instead, this semantics makes propagation of `nonnull` to caller illegal. The reason is that, passing poison to `nonnull` does not immediately raise UB anymore, so such program is still well defined, if the callee does not use the argument. Having `noundef` attribute there re-allows this. ``` define void @f(i8* %p) { ; functionattr cannot mark %p nonnull here anymore call void @g(i8* nonnull %p) ; .. because @g never raises UB if it never uses %p. ret void } ``` Another attribute that needs to be updated is `align`. This patch updates the semantics of align to accept poison as well. Reviewed By: jdoerfert Differential Revision: https://reviews.llvm.org/D90529		2021-01-20 11:31:23 +09:00
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llvm	Allow nonnull/align attribute to accept poison	2021-01-20 11:31:23 +09:00
llvm-c	[X86] Add x86_amx type for intel AMX.	2020-12-30 13:52:13 +08:00