Index: llvm/lib/Target/AArch64/AArch64ISelLowering.h
===================================================================
--- llvm/lib/Target/AArch64/AArch64ISelLowering.h
+++ llvm/lib/Target/AArch64/AArch64ISelLowering.h
@@ -493,11 +493,7 @@
       unsigned OldShiftOpcode, unsigned NewShiftOpcode,
       SelectionDAG &DAG) const override;
 
-  bool shouldExpandShift(SelectionDAG &DAG, SDNode *N) const override {
-    if (DAG.getMachineFunction().getFunction().hasMinSize())
-      return false;
-    return true;
-  }
+  bool shouldExpandShift(SelectionDAG &DAG, SDNode *N) const override;
 
   bool shouldTransformSignedTruncationCheck(EVT XVT,
                                             unsigned KeptBits) const override {
Index: llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -12123,6 +12123,14 @@
   return X.getValueType().isScalarInteger() || NewShiftOpcode == ISD::SHL;
 }
 
+bool AArch64TargetLowering::shouldExpandShift(SelectionDAG &DAG,
+                                              SDNode *N) const {
+  if (DAG.getMachineFunction().getFunction().hasMinSize() &&
+      !Subtarget->isTargetWindows())
+    return false;
+  return true;
+}
+
 void AArch64TargetLowering::initializeSplitCSR(MachineBasicBlock *Entry) const {
   // Update IsSplitCSR in AArch64unctionInfo.
   AArch64FunctionInfo *AFI = Entry->getParent()->getInfo<AArch64FunctionInfo>();
Index: llvm/lib/Target/X86/X86ISelLowering.h
===================================================================
--- llvm/lib/Target/X86/X86ISelLowering.h
+++ llvm/lib/Target/X86/X86ISelLowering.h
@@ -873,11 +873,7 @@
       return VTIsOk(XVT) && VTIsOk(KeptBitsVT);
     }
 
-    bool shouldExpandShift(SelectionDAG &DAG, SDNode *N) const override {
-      if (DAG.getMachineFunction().getFunction().hasMinSize())
-        return false;
-      return true;
-    }
+    bool shouldExpandShift(SelectionDAG &DAG, SDNode *N) const override;
 
     bool shouldSplatInsEltVarIndex(EVT VT) const override;
 
Index: llvm/lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- llvm/lib/Target/X86/X86ISelLowering.cpp
+++ llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -5104,6 +5104,14 @@
   return true;
 }
 
+bool X86TargetLowering::shouldExpandShift(SelectionDAG &DAG,
+                                          SDNode *N) const {
+  if (DAG.getMachineFunction().getFunction().hasMinSize() &&
+      !Subtarget.isOSWindows())
+    return false;
+  return true;
+}
+
 bool X86TargetLowering::shouldSplatInsEltVarIndex(EVT VT) const {
   // Any legal vector type can be splatted more efficiently than
   // loading/spilling from memory.
Index: llvm/test/CodeGen/AArch64/shift_minsize.ll
===================================================================
--- llvm/test/CodeGen/AArch64/shift_minsize.ll
+++ llvm/test/CodeGen/AArch64/shift_minsize.ll
@@ -1,5 +1,10 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
 ; RUN: llc < %s -mtriple=aarch64-unknown-unknown | FileCheck %s
+; RUN: llc < %s -mtriple=aarch64-windows         | FileCheck %s -check-prefix=CHECK-WIN
+
+; The Windows runtime doesn't have these.
+; CHECK-WIN-NOT: __ashlti3
+; CHECK-WIN-NOT: __ashrti3
 
 define i64 @f0(i64 %val, i64 %amt) minsize optsize {
 ; CHECK-LABEL: f0:
@@ -53,6 +58,7 @@
 ; CHECK-NEXT:    bl __ashlti3
 ; CHECK-NEXT:    ldr x30, [sp], #16 // 8-byte Folded Reload
 ; CHECK-NEXT:    ret
+
 entry:
   %x.sroa.2.0.insert.ext = zext i64 %x.coerce1 to i128
   %x.sroa.2.0.insert.shift = shl nuw i128 %x.sroa.2.0.insert.ext, 64
Index: llvm/test/CodeGen/X86/shift_minsize.ll
===================================================================
--- llvm/test/CodeGen/X86/shift_minsize.ll
+++ llvm/test/CodeGen/X86/shift_minsize.ll
@@ -1,5 +1,11 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc < %s -mtriple=x86_64-unknown | FileCheck %s
+; RUN: llc < %s -mtriple=x86_64-unknown       | FileCheck %s
+; RUN: llc < %s -mtriple=x86_64--windows-msvc | FileCheck %s -check-prefix=CHECK-WIN
+
+; The Windows runtime doesn't have these.
+; CHECK-WIN-NOT: __ashlti3
+; CHECK-WIN-NOT: __ashrti3
+; CHECK-WIN-NOT: __lshrti3
 
 define i64 @f0(i64 %val, i64 %amt) minsize optsize {
 ; CHECK-LABEL: f0: