[arm][darwin] Don't generate libcalls for wide shifts on Darwin

Similar to ceb8016.

Darwin doesn't always use compiler-rt, and so we can't assume that these
functions are available on arm.

Author: hyp

llvm/lib/Target/ARM/ARMISelLowering.cpp

@@ -17958,7 +17958,8 @@ bool ARMTargetLowering::isCheapToSpeculateCtlz() const {
 }
 
 bool ARMTargetLowering::shouldExpandShift(SelectionDAG &DAG, SDNode *N) const {
-  return !Subtarget->hasMinSize() || Subtarget->isTargetWindows();
+  return !Subtarget->hasMinSize() || Subtarget->isTargetWindows() ||
+         Subtarget->isTargetDarwin();
 }
 
 Value *ARMTargetLowering::emitLoadLinked(IRBuilder<> &Builder, Value *Addr,

llvm/test/CodeGen/ARM/shift_minsize.ll

@@ -1,11 +1,16 @@
 ; RUN: llc -mtriple=arm-eabi        %s -o - | FileCheck %s
 ; RUN: llc -mtriple=thumbv7-windows %s -o - | FileCheck %s -check-prefix=CHECK-WIN
+; RUN: llc < %s -mtriple=aarch64-apple-darwin    | FileCheck %s -check-prefix=CHECK-DARWIN
 
 ; The Windows runtime doesn't have these.
 ; CHECK-WIN-NOT: __ashldi3
 ; CHECK-WIN-NOT: __ashrdi3
 ; CHECK-WIN-NOT: __lshrdi3
 
+; Darwin compiler-rt excludes these.
+; CHECK-DARWIN-NOT: __ashlti3
+; CHECK-DARWIN-NOT: __ashrti3
+
 define i64 @f0(i64 %val, i64 %amt) minsize optsize {
 ; CHECK-LABEL:   f0:
 ; CHECK:         bl  __aeabi_llsl