[repro] flash_attn_generic: concise causal-mask loop trips dynamic-if…#763
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[repro] flash_attn_generic: concise causal-mask loop trips dynamic-if…#763xudoyuan wants to merge 1 commit into
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… list-carry
Collapses the 112-line hand-unrolled causal mask (s_raw_lo_0..15 /
s_raw_hi_0..15) into a range_constexpr(16) loop. This is the intended
concise form but it currently FAILS at compile time:
TypeError: state variable 's_raw_lo' is list, not an MLIR Value;
stateful dynamic if requires MLIR-backed values.
Suspected FlyDSL compile-time defect: `tile_needs_mask` is a runtime
value, so `if tile_needs_mask:` lowers to a dynamic scf.if. The
if-rewriter can carry a reassigned *named scalar* MLIR value out of the
branch, but not a reassigned *list* local. The original 112-line unroll
existed solely to work around this (carry 16+16 named scalars).
Committed intentionally as a minimal repro so the rewriter can be fixed
to carry list-typed locals (flatten to per-element scf.if yields). Once
fixed, this is the desired form. Does NOT build as-is.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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… list-carry
Collapses the 112-line hand-unrolled causal mask (s_raw_lo_0..15 / s_raw_hi_0..15) into a range_constexpr(16) loop. This is the intended concise form but it currently FAILS at compile time:
TypeError: state variable 's_raw_lo' is list, not an MLIR Value;
stateful dynamic if requires MLIR-backed values.
Suspected FlyDSL compile-time defect:
tile_needs_maskis a runtime value, soif tile_needs_mask:lowers to a dynamic scf.if. The if-rewriter can carry a reassigned named scalar MLIR value out of the branch, but not a reassigned list local. The original 112-line unroll existed solely to work around this (carry 16+16 named scalars).Committed intentionally as a minimal repro so the rewriter can be fixed to carry list-typed locals (flatten to per-element scf.if yields). Once fixed, this is the desired form. Does NOT build as-is.
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