[llvm-branch-commits] [llvm] [AArch64] Split large loop dependence masks (PR #153187)

[Sam Tebbs via llvm-branch-commits]

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@@ -5247,50 +5247,85 @@ SDValue
 AArch64TargetLowering::LowerLOOP_DEPENDENCE_MASK(SDValue Op,
                                                  SelectionDAG &DAG) const {
   SDLoc DL(Op);
-  uint64_t EltSize = Op.getConstantOperandVal(2);
-  EVT VT = Op.getValueType();
-  switch (EltSize) {
-  case 1:
-    if (VT != MVT::v16i8 && VT != MVT::nxv16i1)
-      return SDValue();
-    break;
-  case 2:
-    if (VT != MVT::v8i8 && VT != MVT::nxv8i1)
-      return SDValue();
-    break;
-  case 4:
-    if (VT != MVT::v4i16 && VT != MVT::nxv4i1)
-      return SDValue();
-    break;
-  case 8:
-    if (VT != MVT::v2i32 && VT != MVT::nxv2i1)
-      return SDValue();
-    break;
-  default:
-    // Other element sizes are incompatible with whilewr/rw, so expand instead
-    return SDValue();
-  }
+  assert((Subtarget->hasSVE2() ||
+          (Subtarget->hasSME() && Subtarget->isStreaming())) &&
+         "Lowering loop_dependence_raw_mask or loop_dependence_war_mask "
+         "requires SVE or SME");
+
+  uint64_t EltSizeInBytes = Op.getConstantOperandVal(2);
+  // Other element sizes are incompatible with whilewr/rw, so expand instead
+  if (!is_contained({1u, 2u, 4u, 8u}, EltSizeInBytes))
+    return SDValue();
+
+  EVT FullVT = Op.getValueType();
+  EVT ExtractVT = FullVT;
+  EVT EltVT = MVT::getIntegerVT(EltSizeInBytes * 8);
+  unsigned NumElements = FullVT.getVectorMinNumElements();
+  unsigned PredElements = getPackedSVEVectorVT(EltVT).getVectorMinNumElements();
+  bool Split = NumElements > PredElements;
+
+  if (EltSizeInBytes * NumElements < 16)
+    // The element size and vector length combination must at least form a
+    // 128-bit vector. Shorter vector lengths can be widened then extracted
+    FullVT = FullVT.getDoubleNumVectorElementsVT(*DAG.getContext());
+
+  auto LowerToWhile = [&](EVT VT, unsigned AddrScale) {
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SamTebbs33 wrote:

Done.

https://github.com/llvm/llvm-project/pull/153187