Module dead_store_elim 

Intra-block dead store elimination.

Walks each basic block backward to determine which stack positions are live (will be read by a later instruction or at the block exit). Instructions whose outputs are all dead and whose logic is safe to eliminate are marked InstFlags::NOOP.

DUP, SWAP, POP, DUPN, SWAPN, and EXCHANGE require custom liveness transfer functions because generic (inputs, outputs) arity doesn’t capture how they map stack slots:

• SWAP/SWAPN permute two positions without consuming or producing values.
• DUP/DUPN copy a single deep source to a new TOS.
• EXCHANGE swaps two arbitrary non-TOS positions.
• POP kills its input (makes the position dead) rather than reading it.

Enums

DecodedImm 🔒

Decoded immediate for liveness transfer of DUPN/SWAPN/EXCHANGE.

Functions

all_outputs_dead 🔒

Returns true if all positions actually written by the instruction are dead.

can_skip_when_dead 🔒

Returns true if the opcode’s logic is safe to skip when its outputs are dead.

generic_transfer 🔒

Generic liveness transfer: kill all outputs, then mark all inputs as live.

swap_all_dead 🔒

SWAP dead check: both TOS and the swapped position must be dead.

transfer_dup 🔒

DUP liveness: the new TOS is killed; if it was live, the source becomes live.

transfer_liveness 🔒

Backward liveness transfer for a single instruction.

transfer_swap 🔒

SWAP liveness: permute liveness of TOS and the swapped position.