[FastISel][ARM] Use MOVT/MOVW if the subtarget requests it.

This change is also in preparation for a future change to make sure that
the constant materialization uses MOVT/MOVW when available and not a load
from the constant pool.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215584 91177308-0d34-0410-b5e6-96231b3b80d8

Author: ributzka

lib/Target/ARM/ARMFastISel.cpp

@@ -546,6 +546,9 @@ unsigned ARMFastISel::ARMMaterializeInt(const Constant *C, MVT VT) {
     }
   }
 
+  if (Subtarget->useMovt(*FuncInfo.MF))
+    return FastEmit_i(VT, VT, ISD::Constant, CI->getZExtValue());
+
   // Load from constant pool.  For now 32-bit only.
   if (VT != MVT::i32)
     return false;

test/CodeGen/ARM/fast-isel-mvn.ll

@@ -1,5 +1,5 @@
-; RUN: llc < %s -O0 -verify-machineinstrs -fast-isel-abort -relocation-model=dynamic-no-pic -mtriple=armv7-apple-ios | FileCheck %s --check-prefix=ARM
-; RUN: llc < %s -O0 -verify-machineinstrs -fast-isel-abort -relocation-model=dynamic-no-pic -mtriple=armv7-linux-gnueabi | FileCheck %s --check-prefix=ARM
+; RUN: llc -O0 -verify-machineinstrs -fast-isel-abort -relocation-model=dynamic-no-pic -arm-use-movt=false -mtriple=armv7-apple-ios     < %s | FileCheck %s --check-prefix=CHECK --check-prefix=ARM
+; RUN: llc -O0 -verify-machineinstrs -fast-isel-abort -relocation-model=dynamic-no-pic -arm-use-movt=false -mtriple=armv7-linux-gnueabi < %s | FileCheck %s --check-prefix=CHECK --check-prefix=ARM
 ; RUN: llc < %s -O0 -verify-machineinstrs -fast-isel-abort -relocation-model=dynamic-no-pic -mtriple=thumbv7-apple-ios | FileCheck %s --check-prefix=THUMB
 ; rdar://10412592