[llvm] eaa8af9 - GlobalISel: Add helper for constructing load from offset

[Matt Arsenault via llvm-commits]

Author: Matt Arsenault
Date: 2020-06-05T15:06:03-04:00
New Revision: eaa8af93228c1e1bce078d66605db83b26eda8e5

URL: https://github.com/llvm/llvm-project/commit/eaa8af93228c1e1bce078d66605db83b26eda8e5
DIFF: https://github.com/llvm/llvm-project/commit/eaa8af93228c1e1bce078d66605db83b26eda8e5.diff

LOG: GlobalISel: Add helper for constructing load from offset

Added: 
    

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

Removed: 
    


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diff  --git a/llvm/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h b/llvm/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
index 0252a324de23..ae28d728a16d 100644
--- a/llvm/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
@@ -804,6 +804,14 @@ class MachineIRBuilder {
   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.

diff  --git a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
index 6e53ec2bb46e..4236fdd82084 100644
--- a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
@@ -376,6 +376,23 @@ MachineInstrBuilder MachineIRBuilder::buildLoadInstr(unsigned Opcode,
   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) {