[Mlir-commits] [clang] [llvm] [mlir] [AArch64][SME] Remove immediate argument restriction for svldr and svstr (PR #68565)

[Sander de Smalen]

================
@@ -4850,6 +4852,93 @@ SDValue AArch64TargetLowering::getPStateSM(SelectionDAG &DAG, SDValue Chain,
                      Mask);
 }
 
+// Lower an SME LDR/STR ZA intrinsic to LDR_ZA_PSEUDO or STR_ZA.
+// Case 1: If the vector number (vecnum) is an immediate in range, it gets
+// folded into the instruction
+//    ldr(%tileslice, %ptr, 11) -> ldr [%tileslice, 11], [%ptr, 11]
+// Case 2: If the vecnum is not an immediate, then it is used to modify the base
+// and tile slice registers
+//    ldr(%tileslice, %ptr, %vecnum)
+//    ->
+//    %svl = rdsvl
+//    %ptr2 = %ptr + %svl * %vecnum
+//    %tileslice2 = %tileslice + %vecnum
+//    ldr [%tileslice2, 0], [%ptr2, 0]
+// Case 3: If the vecnum is an immediate out of range, then the same is done as
+// case 2, but the base and slice registers are modified by the greatest
+// multiple of 15 lower than the vecnum and the remainder is folded into the
+// instruction. This means that successive loads and stores that are offset from
+// each other can share the same base and slice register updates.
+//    ldr(%tileslice, %ptr, 22)
+//    ldr(%tileslice, %ptr, 23)
+//    ->
+//    %svl = rdsvl
+//    %ptr2 = %ptr + %svl * 15
+//    %tileslice2 = %tileslice + 15
+//    ldr [%tileslice2, 7], [%ptr2, 7]
+//    ldr [%tileslice2, 8], [%ptr2, 8]
+// Case 4: If the vecnum is an add of an immediate, then the non-immediate
+// operand and the immediate can be folded into the instruction, like case 2.
+//    ldr(%tileslice, %ptr, %vecnum + 7)
+//    ldr(%tileslice, %ptr, %vecnum + 8)
+//    ->
+//    %svl = rdsvl
+//    %ptr2 = %ptr + %svl * %vecnum
+//    %tileslice2 = %tileslice + %vecnum
+//    ldr [%tileslice2, 7], [%ptr2, 7]
+//    ldr [%tileslice2, 8], [%ptr2, 8]
+// Case 5: The vecnum being an add of an immediate out of range is also handled,
+// in which case the same remainder logic as case 3 is used.
+SDValue LowerSMELdrStr(SDValue N, SelectionDAG &DAG, bool IsLoad) {
+  SDLoc DL(N);
+
+  SDValue TileSlice = N->getOperand(2);
+  SDValue Base = N->getOperand(3);
+  SDValue VecNum = N->getOperand(4);
+  int32_t ConstAddend = 0;
+  SDValue VarAddend = VecNum;
+
+  // If the vnum is an add of an immediate, we can fold it into the instruction
+  if (VecNum.getOpcode() == ISD::ADD &&
+      isa<ConstantSDNode>(VecNum.getOperand(1))) {
+    ConstAddend = cast<ConstantSDNode>(VecNum.getOperand(1))->getSExtValue();
+    VarAddend = VecNum.getOperand(0);
+  } else if (auto ImmNode = dyn_cast<ConstantSDNode>(VecNum)) {
+    ConstAddend = ImmNode->getSExtValue();
+    VarAddend = SDValue();
+  }
+
+  int32_t ImmAddend = ConstAddend % 16;
+  if (int32_t C = (ConstAddend - ImmAddend)) {
+    SDValue CVal = DAG.getTargetConstant(C, DL, MVT::i32);
+    VarAddend = VarAddend
+                    ? DAG.getNode(ISD::ADD, DL, MVT::i32, {VarAddend, CVal})
+                    : CVal;
+  }
+
+  if (VarAddend) {
+    // Get the vector length that will be multiplied by vnum
+    auto SVL = DAG.getNode(AArch64ISD::RDSVL, DL, MVT::i64,
+                           DAG.getConstant(1, DL, MVT::i32));
+
+    // Multiply SVL and vnum then add it to the base
+    SDValue Mul = DAG.getNode(
+        ISD::MUL, DL, MVT::i64,
+        {SVL, DAG.getNode(ISD::SIGN_EXTEND, DL, MVT::i64, VarAddend)});
+    Base = DAG.getNode(ISD::ADD, DL, MVT::i64, {Base, Mul});
+    // Just add vnum to the tileslice
+    TileSlice = DAG.getNode(ISD::ADD, DL, MVT::i32, {TileSlice, VarAddend});
+  }
+
+  SmallVector<SDValue, 4> Ops = {
+      /*Chain=*/N.getOperand(0), TileSlice, Base,
+      DAG.getTargetConstant(ImmAddend, DL, MVT::i32)};
----------------
sdesmalen-arm wrote:

nit: you might as well inline Ops into the expression below.

https://github.com/llvm/llvm-project/pull/68565