diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.h b/llvm/lib/Target/RISCV/RISCVISelLowering.h
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.h
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.h
@@ -119,6 +119,8 @@
       return false;
     return true;
   }
+  bool isDesirableToCommuteWithShift(const SDNode *N,
+                                     CombineLevel Level) const override;
 
 private:
   void analyzeInputArgs(MachineFunction &MF, CCState &CCInfo,
diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -841,6 +841,22 @@
   return SDValue();
 }
 
+bool RISCVTargetLowering::isDesirableToCommuteWithShift(
+    const SDNode *N, CombineLevel Level) const {
+  // The following folds are only desirable if constant `c1` cannot fit into an
+  // immediate:
+  //   (shl (add x, c1), c2) -> (add (shl x, c2), c1 << c2)
+  //   (shl (or x, c1), c2) -> (or (shl x, c2), c1 << c2)
+  SDValue N0 = N->getOperand(0);
+  if (N0.getOpcode() == ISD::ADD || N0.getOpcode() == ISD::OR) {
+    SDValue C1 = N0->getOperand(1);
+    if (auto *Const = dyn_cast<ConstantSDNode>(C1)) {
+      return !isLegalAddImmediate(Const->getSExtValue());
+    }
+  }
+  return true;
+}
+
 unsigned RISCVTargetLowering::ComputeNumSignBitsForTargetNode(
     SDValue Op, const APInt &DemandedElts, const SelectionDAG &DAG,
     unsigned Depth) const {
diff --git a/llvm/test/CodeGen/RISCV/add-before-shl.ll b/llvm/test/CodeGen/RISCV/add-before-shl.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/add-before-shl.ll
@@ -0,0 +1,87 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=riscv32 -verify-machineinstrs < %s \
+; RUN:   | FileCheck -check-prefix=RV32I %s
+; RUN: llc -mtriple=riscv64 -verify-machineinstrs < %s \
+; RUN:   | FileCheck -check-prefix=RV64I %s
+
+; These test that constant adds are not moved after shifts by DAGCombine,
+; if the constant can fit into an immediate.
+;
+; Materialising the large (shifted) constant produced for the new add
+; uses an extra register, and takes several instructions. It is more
+; efficient to perform the add before the shift if the constant to be
+; added fits into an immediate.
+
+define signext i32 @add_small_const(i32 signext %a) nounwind {
+; RV32I-LABEL: add_small_const:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    addi a0, a0, 1
+; RV32I-NEXT:    slli a0, a0, 24
+; RV32I-NEXT:    srai a0, a0, 24
+; RV32I-NEXT:    ret
+;
+; RV64I-LABEL: add_small_const:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    addi a0, a0, 1
+; RV64I-NEXT:    slli a0, a0, 56
+; RV64I-NEXT:    srai a0, a0, 56
+; RV64I-NEXT:    ret
+  %1 = add i32 %a, 1
+  %2 = shl i32 %1, 24
+  %3 = ashr i32 %2, 24
+  ret i32 %3
+}
+
+; NOTE: This add constant does not fit into an add immediate, so we allow the
+; the transformation to fire. However, this introduces a second left shift,
+; which we wouldn't need if we did the add before the shl.
+define signext i32 @add_large_const(i32 signext %a) nounwind {
+; RV32I-LABEL: add_large_const:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    slli a0, a0, 16
+; RV32I-NEXT:    lui a1, 65520
+; RV32I-NEXT:    add a0, a0, a1
+; RV32I-NEXT:    srai a0, a0, 16
+; RV32I-NEXT:    ret
+;
+; RV64I-LABEL: add_large_const:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    slli a0, a0, 48
+; RV64I-NEXT:    lui a1, 1
+; RV64I-NEXT:    addiw a1, a1, -1
+; RV64I-NEXT:    slli a1, a1, 48
+; RV64I-NEXT:    add a0, a0, a1
+; RV64I-NEXT:    srai a0, a0, 48
+; RV64I-NEXT:    ret
+  %1 = add i32 %a, 4095
+  %2 = shl i32 %1, 16
+  %3 = ashr i32 %2, 16
+  ret i32 %3
+}
+
+; NOTE: This add constant does not fit into an add immediate, so we allow the
+; the transformation to fire. However, this introduces a second left shift,
+; which we wouldn't need if we did the add before the shl.
+define signext i32 @add_huge_const(i32 signext %a) nounwind {
+; RV32I-LABEL: add_huge_const:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    slli a0, a0, 16
+; RV32I-NEXT:    lui a1, 524272
+; RV32I-NEXT:    add a0, a0, a1
+; RV32I-NEXT:    srai a0, a0, 16
+; RV32I-NEXT:    ret
+;
+; RV64I-LABEL: add_huge_const:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    slli a0, a0, 48
+; RV64I-NEXT:    lui a1, 8
+; RV64I-NEXT:    addiw a1, a1, -1
+; RV64I-NEXT:    slli a1, a1, 48
+; RV64I-NEXT:    add a0, a0, a1
+; RV64I-NEXT:    srai a0, a0, 48
+; RV64I-NEXT:    ret
+  %1 = add i32 %a, 32767
+  %2 = shl i32 %1, 16
+  %3 = ashr i32 %2, 16
+  ret i32 %3
+}