[PATCH] D130248: [LoongArch] Offset folding for frameindex
Ray Wang via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Mon Jul 25 05:37:40 PDT 2022
wangleiat added a comment.
In D130248#3674149 <https://reviews.llvm.org/D130248#3674149>, @barannikov88 wrote:
> In D130248#3674127 <https://reviews.llvm.org/D130248#3674127>, @MaskRay wrote:
>
>> Do you know why csky/hexagon need `isOrEquivalentToAdd` while other targets can produce efficient code without `isOrEquivalentToAdd` ?
>
> Other targets just do that manually in *ISelDAGToDAG.cpp file. E.g. X86:
>
> case ISD::OR:
> // We want to look through a transform in InstCombine and DAGCombiner that
> // turns 'add' into 'or', so we can treat this 'or' exactly like an 'add'.
> // Example: (or (and x, 1), (shl y, 3)) --> (add (and x, 1), (shl y, 3))
> // An 'lea' can then be used to match the shift (multiply) and add:
> // and $1, %esi
> // lea (%rsi, %rdi, 8), %rax
> if (CurDAG->haveNoCommonBitsSet(N.getOperand(0), N.getOperand(1)) &&
> !matchAdd(N, AM, Depth))
> return false;
> break;
>
> ARM:
>
> // Determine whether an ISD::OR's operands are suitable to turn the operation
> // into an addition, which often has more compact encodings.
> bool ARMDAGToDAGISel::SelectAddLikeOr(SDNode *Parent, SDValue N, SDValue &Out) {
> assert(Parent->getOpcode() == ISD::OR && "unexpected parent");
> Out = N;
> return CurDAG->haveNoCommonBitsSet(N, Parent->getOperand(1));
> }
Agree, The `DAGCombiner` will almost certainly be generated `ISD::OR` operator for frameindex. (natural alignment attribute?)
================
Comment at: llvm/lib/Target/LoongArch/LoongArchInstrInfo.td:591
+/// Predicates
+def IsOrAdd: PatFrag<(ops node:$A, node:$B), (or node:$A, node:$B), [{
+ return isOrEquivalentToAdd(N);
----------------
barannikov88 wrote:
> You can check for both ADD and OR in one PatFrags, e.g.:
> ```
> def add_like : PatFrags<(ops node:$lhs, node:$rhs),
> [(add $lhs, $rhs), (or $lhs, $rhs)], [{
> return N->getOpcode() == ISD::ADD || isOrEquivalentToAdd(N);
> }]>;
> ```
> This will halve the number of patterns. Up to you, of course.
> You can check for both ADD and OR in one PatFrags, e.g.:
> ```
> def add_like : PatFrags<(ops node:$lhs, node:$rhs),
> [(add $lhs, $rhs), (or $lhs, $rhs)], [{
> return N->getOpcode() == ISD::ADD || isOrEquivalentToAdd(N);
> }]>;
> ```
> This will halve the number of patterns. Up to you, of course.
Thanks, I will do that.
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