[llvm] [RISCV] Handle .vx/.vi pseudos in hasAllNBitUsers (PR #67419)

[Philip Reames via llvm-commits]

================
@@ -2752,6 +2752,175 @@ bool RISCVDAGToDAGISel::selectSHXADD_UWOp(SDValue N, unsigned ShAmt,
   return false;
 }
 
+static bool vectorPseudoHasAllNBitUsers(SDNode *User, unsigned UserOpNo,
+                                        unsigned Bits,
+                                        const TargetInstrInfo *TII) {
+  const RISCVVPseudosTable::PseudoInfo *PseudoInfo =
+      RISCVVPseudosTable::getPseudoInfo(User->getMachineOpcode());
+
+  if (!PseudoInfo)
+    return false;
+
+  const MCInstrDesc &MCID = TII->get(User->getMachineOpcode());
+  const uint64_t TSFlags = MCID.TSFlags;
+  if (!RISCVII::hasSEWOp(TSFlags))
+    return false;
+  assert(RISCVII::hasVLOp(TSFlags));
+
+  bool HasGlueOp = User->getGluedNode() != nullptr;
+  unsigned ChainOpIdx = User->getNumOperands() - HasGlueOp - 1;
+  bool HasChainOp = User->getOperand(ChainOpIdx).getValueType() == MVT::Other;
+  bool HasVecPolicyOp = RISCVII::hasVecPolicyOp(TSFlags);
+  unsigned VLIdx =
+      User->getNumOperands() - HasVecPolicyOp - HasChainOp - HasGlueOp - 2;
+  const unsigned Log2SEW = User->getConstantOperandVal(VLIdx + 1);
+
+  // TODO: The Largest VL 65,536 occurs for LMUL=8 and SEW=8 with
+  // VLEN=65,536. We could check if Bits < 16 here.
+  if (UserOpNo == VLIdx)
----------------
preames wrote:

Isn't it though?  The largest AVL supported by the vsetvli will still be bounded, and we don't split instructions to support larger AVLs.  As such, don't we know that either AVL is bounded or we have UB?

https://github.com/llvm/llvm-project/pull/67419