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[AArch64][SVE] Remove chains of unnecessary SVE reinterpret intrinsics
This commit extends SVEIntrinsicOpts::optimizeConvertFromSVBool to
identify and remove longer chains of redundant SVE reintepret
intrinsics. For example, the following chain of redundant SVE
reinterprets is now recognised as redundant:
%a = <vscale x 2 x i1>
%1 = <vscale x 16 x i1> @llvm.aarch64.sve.convert.to.svbool(<vscale x 2 x i1> %a)
%2 = <vscale x 4 x i1> @llvm.aarch64.sve.convert.from.svbool(<vscale x 16 x i1> %1)
%3 = <vscale x 16 x i1> @llvm.aarch64.sve.convert.to.svbool(<vscale x 4 x i1> %2)
%4 = <vscale x 4 x i1> @llvm.aarch64.sve.convert.from.svbool(<vscale x 16 x i1> %3)
%5 = <vscale x 16 x i1> @llvm.aarch64.sve.convert.to.svbool(<vscale x 4 x i1> %4)
%6 = <vscale x 2 x i1> @llvm.aarch64.sve.convert.from.svbool(<vscale x 16 x i1> %5)
ret <vscale x 2 x i1> %6
and will be replaced with:
ret <vscale x 2 x i1> %a
Eliminating these can sometimes mean emitting fewer unnecessary
loads/stores when lowering to assembly.
Differential Revision: https://reviews.llvm.org/D94074
This commit is contained in:
Joe Ellis
parent
1d15e5fce3
commit
7f6a519103
@ -177,22 +177,50 @@ bool SVEIntrinsicOpts::optimizeConvertFromSVBool(IntrinsicInst *I) {
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if (isa<PHINode>(I->getArgOperand(0)))
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return processPhiNode(I);
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// If we have a reinterpret intrinsic I of type A which is converting from
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// another reinterpret Y of type B, and the source type of Y is A, then we can
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// elide away both reinterprets if there are no other users of Y.
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auto *Y = isReinterpretToSVBool(I->getArgOperand(0));
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if (!Y)
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SmallVector<Instruction *, 32> CandidatesForRemoval;
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Value *Cursor = I->getOperand(0), *EarliestReplacement = nullptr;
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const auto *IVTy = cast<VectorType>(I->getType());
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// Walk the chain of conversions.
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while (Cursor) {
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// If the type of the cursor has fewer lanes than the final result, zeroing
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// must take place, which breaks the equivalence chain.
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const auto *CursorVTy = cast<VectorType>(Cursor->getType());
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if (CursorVTy->getElementCount().getKnownMinValue() <
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IVTy->getElementCount().getKnownMinValue())
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break;
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// If the cursor has the same type as I, it is a viable replacement.
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if (Cursor->getType() == IVTy)
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EarliestReplacement = Cursor;
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auto *IntrinsicCursor = dyn_cast<IntrinsicInst>(Cursor);
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// If this is not an SVE conversion intrinsic, this is the end of the chain.
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if (!IntrinsicCursor || !(IntrinsicCursor->getIntrinsicID() ==
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Intrinsic::aarch64_sve_convert_to_svbool ||
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IntrinsicCursor->getIntrinsicID() ==
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Intrinsic::aarch64_sve_convert_from_svbool))
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break;
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CandidatesForRemoval.insert(CandidatesForRemoval.begin(), IntrinsicCursor);
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Cursor = IntrinsicCursor->getOperand(0);
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}
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// If no viable replacement in the conversion chain was found, there is
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// nothing to do.
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if (!EarliestReplacement)
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return false;
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Value *SourceVal = Y->getArgOperand(0);
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if (I->getType() != SourceVal->getType())
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return false;
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I->replaceAllUsesWith(SourceVal);
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I->replaceAllUsesWith(EarliestReplacement);
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I->eraseFromParent();
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if (Y->use_empty())
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Y->eraseFromParent();
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while (!CandidatesForRemoval.empty()) {
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Instruction *Candidate = CandidatesForRemoval.pop_back_val();
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if (Candidate->use_empty())
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Candidate->eraseFromParent();
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}
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return true;
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}
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@ -67,6 +67,62 @@ define <vscale x 16 x i1> @reinterpret_test_d_rev(<vscale x 16 x i1> %a) {
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ret <vscale x 16 x i1> %2
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}
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define <vscale x 2 x i1> @reinterpret_test_full_chain(<vscale x 2 x i1> %a) {
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; OPT-LABEL: @reinterpret_test_full_chain(
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; OPT: ret <vscale x 2 x i1> %a
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%1 = tail call <vscale x 16 x i1> @llvm.aarch64.sve.convert.to.svbool.nxv2i1(<vscale x 2 x i1> %a)
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%2 = tail call <vscale x 4 x i1> @llvm.aarch64.sve.convert.from.svbool.nxv4i1(<vscale x 16 x i1> %1)
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%3 = tail call <vscale x 16 x i1> @llvm.aarch64.sve.convert.to.svbool.nxv4i1(<vscale x 4 x i1> %2)
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%4 = tail call <vscale x 4 x i1> @llvm.aarch64.sve.convert.from.svbool.nxv4i1(<vscale x 16 x i1> %3)
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%5 = tail call <vscale x 16 x i1> @llvm.aarch64.sve.convert.to.svbool.nxv4i1(<vscale x 4 x i1> %4)
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%6 = tail call <vscale x 2 x i1> @llvm.aarch64.sve.convert.from.svbool.nxv2i1(<vscale x 16 x i1> %5)
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ret <vscale x 2 x i1> %6
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}
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; The last two reinterprets are not necessary, since they are doing the same
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; work as the first two.
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define <vscale x 4 x i1> @reinterpret_test_partial_chain(<vscale x 2 x i1> %a) {
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; OPT-LABEL: @reinterpret_test_partial_chain(
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; OPT: %1 = tail call <vscale x 16 x i1> @llvm.aarch64.sve.convert.to.svbool.nxv2i1(<vscale x 2 x i1> %a)
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; OPT-NEXT: %2 = tail call <vscale x 4 x i1> @llvm.aarch64.sve.convert.from.svbool.nxv4i1(<vscale x 16 x i1> %1)
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; OPT-NEXT: ret <vscale x 4 x i1> %2
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%1 = tail call <vscale x 16 x i1> @llvm.aarch64.sve.convert.to.svbool.nxv2i1(<vscale x 2 x i1> %a)
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%2 = tail call <vscale x 4 x i1> @llvm.aarch64.sve.convert.from.svbool.nxv4i1(<vscale x 16 x i1> %1)
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%3 = tail call <vscale x 16 x i1> @llvm.aarch64.sve.convert.to.svbool.nxv4i1(<vscale x 4 x i1> %2)
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%4 = tail call <vscale x 4 x i1> @llvm.aarch64.sve.convert.from.svbool.nxv4i1(<vscale x 16 x i1> %3)
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ret <vscale x 4 x i1> %4
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}
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; The chain cannot be reduced because of the second reinterpret, which causes
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; zeroing.
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define <vscale x 8 x i1> @reinterpret_test_irreducible_chain(<vscale x 8 x i1> %a) {
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; OPT-LABEL: @reinterpret_test_irreducible_chain(
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; OPT: %1 = tail call <vscale x 16 x i1> @llvm.aarch64.sve.convert.to.svbool.nxv8i1(<vscale x 8 x i1> %a)
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; OPT-NEXT: %2 = tail call <vscale x 4 x i1> @llvm.aarch64.sve.convert.from.svbool.nxv4i1(<vscale x 16 x i1> %1)
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; OPT-NEXT: %3 = tail call <vscale x 16 x i1> @llvm.aarch64.sve.convert.to.svbool.nxv4i1(<vscale x 4 x i1> %2)
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; OPT-NEXT: %4 = tail call <vscale x 8 x i1> @llvm.aarch64.sve.convert.from.svbool.nxv8i1(<vscale x 16 x i1> %3)
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; OPT-NEXT: ret <vscale x 8 x i1> %4
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%1 = tail call <vscale x 16 x i1> @llvm.aarch64.sve.convert.to.svbool.nxv8i1(<vscale x 8 x i1> %a)
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%2 = tail call <vscale x 4 x i1> @llvm.aarch64.sve.convert.from.svbool.nxv4i1(<vscale x 16 x i1> %1)
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%3 = tail call <vscale x 16 x i1> @llvm.aarch64.sve.convert.to.svbool.nxv4i1(<vscale x 4 x i1> %2)
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%4 = tail call <vscale x 8 x i1> @llvm.aarch64.sve.convert.from.svbool.nxv8i1(<vscale x 16 x i1> %3)
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ret <vscale x 8 x i1> %4
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}
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; Here, the candidate list is larger than the number of instructions that we
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; end up removing.
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define <vscale x 4 x i1> @reinterpret_test_keep_some_candidates(<vscale x 8 x i1> %a) {
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; OPT-LABEL: @reinterpret_test_keep_some_candidates(
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; OPT: %1 = tail call <vscale x 16 x i1> @llvm.aarch64.sve.convert.to.svbool.nxv8i1(<vscale x 8 x i1> %a)
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; OPT-NEXT: %2 = tail call <vscale x 4 x i1> @llvm.aarch64.sve.convert.from.svbool.nxv4i1(<vscale x 16 x i1> %1)
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; OPT-NEXT: ret <vscale x 4 x i1> %2
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%1 = tail call <vscale x 16 x i1> @llvm.aarch64.sve.convert.to.svbool.nxv8i1(<vscale x 8 x i1> %a)
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%2 = tail call <vscale x 4 x i1> @llvm.aarch64.sve.convert.from.svbool.nxv4i1(<vscale x 16 x i1> %1)
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%3 = tail call <vscale x 16 x i1> @llvm.aarch64.sve.convert.to.svbool.nxv4i1(<vscale x 4 x i1> %2)
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%4 = tail call <vscale x 4 x i1> @llvm.aarch64.sve.convert.from.svbool.nxv4i1(<vscale x 16 x i1> %3)
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ret <vscale x 4 x i1> %4
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}
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define <vscale x 2 x i1> @reinterpret_reductions(i32 %cond, <vscale x 2 x i1> %a, <vscale x 2 x i1> %b, <vscale x 2 x i1> %c) {
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; OPT-LABEL: reinterpret_reductions
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; OPT-NOT: convert
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