Fold accesses through null-pointer views - #2976
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An optional buffer a kernel receives as null sits behind a runtime flag, so its accesses can only execute as undefined behavior: fold loads to a zero of the element type and drop stores. The views and the captured null then die, instead of blocking the kernel on an operand that mixed view types make untypable. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_016zErYp7upmqr4NHfhod9UD
getZeroAttr has no answer for pointer types, so folding a ptr-typed load produced an arith.constant with no value attribute that crashed downstream canonicalization. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_016zErYp7upmqr4NHfhod9UD
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Nine MFEM TUs (restriction, the lininteg family, bilinearform_ext, hybridization_ext, ...) fail to raise under
xla-gpubecause a kernel captures a null pointer for an optional buffer (markers, boundary arrays) whose uses sit behind a runtime flag. The null is viewed throughpointer2memrefat several element types, so the wrapper-operand path can neither type it nor legalize it.Since an access through null can only execute as undefined behavior, the accesses are dynamically dead: fold loads through a null-rooted view to a zero of the element type and drop stores. The views and the captured null then fold away entirely — in the lit test the guarded body reduces to storing the folded zero.
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https://claude.ai/code/session_016zErYp7upmqr4NHfhod9UD