[llvm] [AArch64][GlobalISel] Add support for post-indexed loads/stores. (PR #69532)

[via llvm-commits]

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@@ -945,42 +945,170 @@ void CombinerHelper::applySextInRegOfLoad(
   MI.eraseFromParent();
 }
 
+static Type *getTypeForLLT(LLT Ty, LLVMContext &C) {
+  if (Ty.isVector())
+    return FixedVectorType::get(IntegerType::get(C, Ty.getScalarSizeInBits()),
+                                Ty.getNumElements());
+  return IntegerType::get(C, Ty.getSizeInBits());
+}
+
+/// Return true if 'MI' is a load or a store that may be fold it's address
+/// operand into the load / store addressing mode.
+static bool canFoldInAddressingMode(GLoadStore *MI, const TargetLowering &TLI,
+                                    MachineRegisterInfo &MRI) {
+  TargetLowering::AddrMode AM;
+  auto *MF = MI->getMF();
+  auto *Addr = getOpcodeDef<GPtrAdd>(MI->getPointerReg(), MRI);
+  if (!Addr)
+    return false;
+
+  AM.HasBaseReg = true;
+  auto CstOff = getIConstantVRegVal(Addr->getOffsetReg(), MRI);
+  if (CstOff)
+    AM.BaseOffs = CstOff->getSExtValue(); // [reg +/- imm]
+  else
+    AM.Scale = 1; // [reg +/- reg]
+
+  return TLI.isLegalAddressingMode(
+      MF->getDataLayout(), AM,
+      getTypeForLLT(MI->getMMO().getMemoryType(),
+                    MF->getFunction().getContext()),
+      MI->getMMO().getAddrSpace());
+}
+
+namespace {
+unsigned getIndexedOpc(unsigned LdStOpc) {
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tschuett wrote:

nit: static please

https://github.com/llvm/llvm-project/pull/69532