https://bugs.llvm.org/show_bug.cgi?id=44602
Bug ID: 44602
Summary: [Attributor] Failure to propagate alignment through
PHI when may have null incoming value
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Global Analyses
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
https://godbolt.org/z/jryz4D
define void @square(i1 %c, i32* align 32 %dst) #0 {
br i1 %c, label %truebb, label %falsebb
truebb:
br label %end
falsebb:
br label %end
end:
%ptr = phi i32* [ %dst, %truebb ], [ null, %falsebb ]
store i32 0, i32* %ptr
ret void
}
attributes #0 = { "null-pointer-is-valid"="true" }
Regardless of whether or not null is legal address,
we should annotate that store with `align 32`,
because `%ptr` can either take the value of `i32* align 32 %dst`,
or `null`. Because `null` is *always* aligned - no bits are set.
I might take a stab at this..
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