[AArch64][SVE][InstCombine] Fold redundant zip(unzip) operations

[mnadeem]

Summary

zip1(uzp1(A, B), uzp2(A, B)) --> A
zip2(uzp1(A, B), uzp2(A, B)) --> B

[david-arm]

LGTM. Nice folds!

[paulwalker-arm]

llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp

799

I think the function will be more readable if the names in the code matched the comment, i.e. can these just be A and B? Don't let this hold up the patch, if you agree it's just something to consider before pushing the change.

[mnadeem]

llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp

799

Updated in the final commit.

llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp

static Optional<Instruction *> instCombineSVETBL(InstCombiner &IC,
   auto *Extract = Builder.CreateExtractElement(OpVal, SplatValue);
   auto *VectorSplat =
       Builder.CreateVectorSplat(VTy->getElementCount(), Extract);
 
   VectorSplat->takeName(&II);
   return IC.replaceInstUsesWith(II, VectorSplat);
 }
 
+static Optional<Instruction *> instCombineSVEZip(InstCombiner &IC,
+                                                 IntrinsicInst &II) {
+  // zip1(uzp1(A, B), uzp2(A, B)) --> A
+  // zip2(uzp1(A, B), uzp2(A, B)) --> B
+  Value *A, *B;
+  if (match(II.getArgOperand(0),
+            m_Intrinsic<Intrinsic::aarch64_sve_uzp1>(m_Value(A), m_Value(B))) &&
+      match(II.getArgOperand(1), m_Intrinsic<Intrinsic::aarch64_sve_uzp2>(
+                                     m_Specific(A), m_Specific(B))))
+    return IC.replaceInstUsesWith(
+        II, (II.getIntrinsicID() == Intrinsic::aarch64_sve_zip1 ? A : B));
+
+  return None;
+}
+
 Optional<Instruction *>
 AArch64TTIImpl::instCombineIntrinsic(InstCombiner &IC,
                                      IntrinsicInst &II) const {
   Intrinsic::ID IID = II.getIntrinsicID();
   switch (IID) {
   default:
     break;
   case Intrinsic::aarch64_sve_convert_from_svbool:
case Intrinsic::aarch64_sve_fmul:
     return instCombineSVEVectorMul(IC, II);
   case Intrinsic::aarch64_sve_tbl:
     return instCombineSVETBL(IC, II);
   case Intrinsic::aarch64_sve_uunpkhi:
   case Intrinsic::aarch64_sve_uunpklo:
   case Intrinsic::aarch64_sve_sunpkhi:
   case Intrinsic::aarch64_sve_sunpklo:
     return instCombineSVEUnpack(IC, II);
+  case Intrinsic::aarch64_sve_zip1:
+  case Intrinsic::aarch64_sve_zip2:
+    return instCombineSVEZip(IC, II);
   }
 
   return None;
 }
 
 bool AArch64TTIImpl::isWideningInstruction(Type *DstTy, unsigned Opcode,
                                            ArrayRef<const Value *> Args) {
 

llvm/test/Transforms/InstCombine/AArch64/sve-intrinsic-opts-zip.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -instcombine < %s | FileCheck %s
+
+target triple = "aarch64-unknown-linux-gnu"
+
+define <vscale x 4 x i32> @redundant_zip_unzip(<vscale x 4 x i32> %a, <vscale x 4 x i32> %b) #0 {
+; CHECK-LABEL: @redundant_zip_unzip(
+; CHECK-NEXT:    [[RET:%.*]] = add <vscale x 4 x i32> [[A:%.*]], [[B:%.*]]
+; CHECK-NEXT:    ret <vscale x 4 x i32> [[RET]]
+;
+  %uzp1 = call <vscale x 4 x i32> @llvm.aarch64.sve.uzp1.nxv4i32(<vscale x 4 x i32> %a, <vscale x 4 x i32> %b)
+  %uzp2 = call <vscale x 4 x i32> @llvm.aarch64.sve.uzp2.nxv4i32(<vscale x 4 x i32> %a, <vscale x 4 x i32> %b)
+  %zip1 = call <vscale x 4 x i32> @llvm.aarch64.sve.zip1.nxv4i32(<vscale x 4 x i32> %uzp1, <vscale x 4 x i32> %uzp2)
+  %zip2 = call <vscale x 4 x i32> @llvm.aarch64.sve.zip2.nxv4i32(<vscale x 4 x i32> %uzp1, <vscale x 4 x i32> %uzp2)
+  %ret = add <vscale x 4 x i32> %zip1, %zip2
+  ret <vscale x 4 x i32> %ret
+}
+
+declare <vscale x 4 x i32> @llvm.aarch64.sve.uzp1.nxv4i32(<vscale x 4 x i32>, <vscale x 4 x i32>)
+declare <vscale x 4 x i32> @llvm.aarch64.sve.uzp2.nxv4i32(<vscale x 4 x i32>, <vscale x 4 x i32>)
+declare <vscale x 4 x i32> @llvm.aarch64.sve.zip1.nxv4i32(<vscale x 4 x i32>, <vscale x 4 x i32>)
+declare <vscale x 4 x i32> @llvm.aarch64.sve.zip2.nxv4i32(<vscale x 4 x i32>, <vscale x 4 x i32>)
+
+attributes #0 = { "target-features"="+sve" }