[llvm] [RISCV] Fold `addi` into load / store even if they are in different BBs. (PR #67024)

[Michael Maitland via llvm-commits]

================
@@ -2278,6 +2279,81 @@ bool RISCVTargetLowering::isLegalElementTypeForRVV(EVT ScalarTy) const {
   }
 }
 
+static bool tryToFoldInstIntoUse(MachineInstr &UseMI, MachineInstr &MI) {
+
+  if (MI.getOpcode() != RISCV::ADDI)
+    return false;
+  if (!(MI.getOperand(0).isReg() && MI.getOperand(1).isReg()))
+    return false;
+
+  switch (UseMI.getOpcode()) {
+  default:
+    return false;
+  case RISCV::LB:
+  case RISCV::LH:
+  case RISCV::LW:
+  case RISCV::LD:
+  case RISCV::LBU:
+  case RISCV::LHU:
+  case RISCV::SB:
+  case RISCV::SH:
+  case RISCV::SW:
+  case RISCV::SD:
+    break;
+  }
+  MachineOperand &OriginalBaseMO = UseMI.getOperand(1);
+  if (!OriginalBaseMO.isReg())
+    return false;
+  if (OriginalBaseMO.getReg() != MI.getOperand(0).getReg())
+    return false;
+
+  MachineOperand &OriginalOffsetMO = UseMI.getOperand(2);
+  MachineOperand &ADDIOffsetMO = MI.getOperand(2);
+  if (!(OriginalOffsetMO.isImm() && ADDIOffsetMO.isImm()))
----------------
michaelmaitland wrote:

Should this be an assert since we know this instruction is an ADDI?

https://github.com/llvm/llvm-project/pull/67024