[PATCH] D80890: GlobalISel: Add helper for constructing load from offset

[Matt Arsenault via Phabricator via llvm-commits]

arsenm created this revision.
arsenm added reviewers: aemerson, aditya_nandakumar, dsanders, paquette.
Herald added subscribers: hiraditya, rovka, wdng.
Herald added a project: LLVM.

https://reviews.llvm.org/D80890

Files:
  llvm/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
  llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp


Index: llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
===================================================================
--- llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
+++ llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
@@ -376,6 +376,23 @@
   return MIB;
 }
 
+MachineInstrBuilder MachineIRBuilder::buildLoadFromOffset(
+  const DstOp &Dst, const SrcOp &BasePtr,
+  MachineMemOperand &BaseMMO, int64_t Offset) {
+  LLT LoadTy = Dst.getLLTTy(*getMRI());
+  MachineMemOperand *OffsetMMO =
+    getMF().getMachineMemOperand(&BaseMMO, Offset, LoadTy.getSizeInBytes());
+
+  if (Offset == 0) // This may be a size or type changing load.
+    return buildLoad(Dst, BasePtr, *OffsetMMO);
+
+  LLT PtrTy = BasePtr.getLLTTy(*getMRI());
+  LLT OffsetTy = LLT::scalar(PtrTy.getSizeInBits());
+  auto ConstOffset = buildConstant(OffsetTy, Offset);
+  auto Ptr = buildPtrAdd(PtrTy, BasePtr, ConstOffset);
+  return buildLoad(Dst, Ptr, *OffsetMMO);
+}
+
 MachineInstrBuilder MachineIRBuilder::buildStore(const SrcOp &Val,
                                                  const SrcOp &Addr,
                                                  MachineMemOperand &MMO) {
Index: llvm/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
===================================================================
--- llvm/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
+++ llvm/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
@@ -804,6 +804,14 @@
   MachineInstrBuilder buildLoadInstr(unsigned Opcode, const DstOp &Res,
                                      const SrcOp &Addr, MachineMemOperand &MMO);
 
+  // Helper to create a load from a constant offset given a base address. Load
+  // the type of \p Dst from \p Offset from the given base address and memory
+  // operand.
+  MachineInstrBuilder buildLoadFromOffset(const DstOp &Dst,
+                                          const SrcOp &BasePtr,
+                                          MachineMemOperand &BaseMMO,
+                                          int64_t Offset);
+
   /// Build and insert `G_STORE Val, Addr, MMO`.
   ///
   /// Stores the value \p Val to \p Addr.


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