Futhark.Optimise.CSE

This module implements common-subexpression elimination. This module does not actually remove the duplicate, but only replaces one with a diference to the other. E.g:

  let a = x + y
  let b = x + y

becomes:

  let a = x + y
  let b = a

After which copy propagation in the simplifier will actually remove the definition of b.

Our CSE is still rather stupid. No normalisation is performed, so the expressions x+y and y+x will be considered distinct. Furthermore, no expression with its own binding will be considered equal to any other, since the variable names will be distinct. This affects SOACs in particular.

Documentation

performCSE :: (AliasableRep rep, CSEInOp (Op (Aliases rep))) => Bool -> Pass rep rep

Perform CSE on every function in a program.

If the boolean argument is false, the pass will not perform CSE on expressions producing arrays. This should be disabled when the rep has memory information, since at that point arrays have identity beyond their value.

performCSEOnFunDef :: (AliasableRep rep, CSEInOp (Op (Aliases rep))) => Bool -> FunDef rep -> FunDef rep

Perform CSE on a single function.

If the boolean argument is false, the pass will not perform CSE on expressions producing arrays. This should be disabled when the rep has memory information, since at that point arrays have identity beyond their value.

performCSEOnStms :: (AliasableRep rep, CSEInOp (Op (Aliases rep))) => Bool -> Stms rep -> Stms rep

Perform CSE on some statements.

If the boolean argument is false, the pass will not perform CSE on expressions producing arrays. This should be disabled when the rep has memory information, since at that point arrays have identity beyond their value.

class CSEInOp op

The operations that permit CSE.

Minimal complete definition

cseInOp

Instances

(AliasableRep rep, CSEInOp (Op (Aliases rep))) => CSEInOp (SOAC (Aliases rep))

Defined in Futhark.Optimise.CSE

Methods

cseInOp :: SOAC (Aliases rep) -> CSEM rep0 (SOAC (Aliases rep))

(Aliased rep, CSEInOp (Op rep), CSEInOp (op rep)) => CSEInOp (HostOp op rep)

Defined in Futhark.Optimise.CSE

Methods

cseInOp :: HostOp op rep -> CSEM rep0 (HostOp op rep)

(Aliased rep, CSEInOp (Op rep), CSEInOp (op rep)) => CSEInOp (MCOp op rep)

Defined in Futhark.Optimise.CSE

Methods

cseInOp :: MCOp op rep -> CSEM rep0 (MCOp op rep)

CSEInOp (op rep) => CSEInOp (MemOp op rep)

Defined in Futhark.Optimise.CSE

Methods

cseInOp :: MemOp op rep -> CSEM rep0 (MemOp op rep)

CSEInOp (NoOp rep)

Defined in Futhark.Optimise.CSE

Methods

cseInOp :: NoOp rep -> CSEM rep0 (NoOp rep)

(Aliased rep, CSEInOp (Op rep)) => CSEInOp (SegOp lvl rep)

Defined in Futhark.Optimise.CSE

Methods

cseInOp :: SegOp lvl rep -> CSEM rep0 (SegOp lvl rep)