[llvm] [RISCV][GISel] Support select vector load intrinsics (PR #160720)

[Craig Topper via llvm-commits]

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@@ -675,6 +681,109 @@ static void getOperandsForBranch(Register CondReg, RISCVCC::CondCode &CC,
   CC = getRISCVCCFromICmp(Pred);
 }
 
+bool RISCVInstructionSelector::selectIntrinsicWithSideEffects(
+    MachineInstr &I, MachineIRBuilder &MIB) const {
+  // Find the intrinsic ID.
+  unsigned IntrinID = cast<GIntrinsic>(I).getIntrinsicID();
+  // Select the instruction.
+  switch (IntrinID) {
+  default:
+    return false;
+  case Intrinsic::riscv_vlm:
+  case Intrinsic::riscv_vle:
+  case Intrinsic::riscv_vle_mask:
+  case Intrinsic::riscv_vlse:
+  case Intrinsic::riscv_vlse_mask: {
+    bool IsMasked = IntrinID == Intrinsic::riscv_vle_mask ||
+                    IntrinID == Intrinsic::riscv_vlse_mask;
+    bool IsStrided = IntrinID == Intrinsic::riscv_vlse ||
+                     IntrinID == Intrinsic::riscv_vlse_mask;
+    LLT VT = MRI->getType(I.getOperand(0).getReg());
+    unsigned Log2SEW = Log2_32(VT.getScalarSizeInBits());
+
+    // Result vector
+    const Register DstReg = I.getOperand(0).getReg();
+    const TargetRegisterClass *DstRC = getRegClassForTypeOnBank(
+        MRI->getType(DstReg), *RBI.getRegBank(DstReg, *MRI, TRI));
+    if (IsMasked)
+      DstRC = TRI.getNoV0RegClass(DstRC);
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topperc wrote:

Shouldn't we be calling `constrainSelectedInstRegOperands` at the end of this to do this constraining?

https://github.com/llvm/llvm-project/pull/160720