unrecognized-shapeNo recognizer claimed this loop

Reported by --explain after a verdict.

mettle explain unrecognized-shape

The honest fallback. The compiler ruled out every disqualifier it can detect and still found no kernel for the loop, so it says that rather than guessing at a cause.

• What does vectorize, as a checklist: unit-stride accesses, a[i] and not a[i * k]

• int8, int32, float32 or float64 elements

• a straight-line body: no calls, no branches, no allocation

• one of the known shapes: a map (a[i] = expr), a + reduction (s = s + expr), a dot product, or a fill

A loop that meets all of that and still lands here is worth reporting.

Related

• call-in-bodyThe loop body calls a function
• extern-call-in-bodyThe loop body calls an external function
• indirect-callThe loop body calls through a function pointer
• alloc-in-bodyThe loop body allocates
• inline-asmThe loop body contains inline assembly
• control-flowThe loop body branches
• early-exitThe loop can leave before its trip count
• int16-elements16-bit integer elements have no kernel