[ARM] Define a subtarget feature that is used to avoid using movt/movw

pairs for 32-bit immediates.

This change is needed to avoid emitting movt/movw pairs when doing LTO
and do so on a per-function basis.

Out-of-tree projects currently using cl::opt option -arm-use-movt=0 or
false to avoid emitting movt/movw pairs should make changes to add
subtarget feature "+no-movt" (see the changes made to clang in r242368).

rdar://problem/21529937

Differential Revision: http://reviews.llvm.org/D11026

llvm-svn: 242369

1 files changed, 4 insertions, 8 deletions

diff --git a/llvm/lib/Target/ARM/ARMSubtarget.cpp b/llvm/lib/Target/ARM/ARMSubtarget.cpp
index 002c3e9b629..31b65f2bfec 100644
--- a/llvm/lib/Target/ARM/ARMSubtarget.cpp
+++ b/llvm/lib/Target/ARM/ARMSubtarget.cpp
@@ -44,9 +44,6 @@ ReserveR9("arm-reserve-r9", cl::Hidden,
           cl::desc("Reserve R9, making it unavailable as GPR"));
 
 static cl::opt<bool>
-ArmUseMOVT("arm-use-movt", cl::init(true), cl::Hidden);
-
-static cl::opt<bool>
 UseFusedMulOps("arm-use-mulops",
                cl::init(true), cl::Hidden);
 
@@ -148,7 +145,7 @@ void ARMSubtarget::initializeEnvironment() {
   HasThumb2 = false;
   NoARM = false;
   IsR9Reserved = ReserveR9;
-  UseMovt = false;
+  NoMovt = false;
   SupportsTailCall = false;
   HasFP16 = false;
   HasD16 = false;
@@ -215,8 +212,6 @@ void ARMSubtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {
   if (isTargetNaCl())
     stackAlignment = 16;
 
-  UseMovt = hasV6T2Ops() && ArmUseMOVT;
-
   if (isTargetMachO()) {
     IsR9Reserved = ReserveR9 || !HasV6Ops;
     SupportsTailCall = !isTargetIOS() || !getTargetTriple().isOSVersionLT(5, 0);
@@ -337,8 +332,9 @@ bool ARMSubtarget::useMovt(const MachineFunction &MF) const {
   // NOTE Windows on ARM needs to use mov.w/mov.t pairs to materialise 32-bit
   // immediates as it is inherently position independent, and may be out of
   // range otherwise.
-  return UseMovt && (isTargetWindows() ||
-                     !MF.getFunction()->hasFnAttribute(Attribute::MinSize));
+  return !NoMovt && hasV6T2Ops() &&
+         (isTargetWindows() ||
+          !MF.getFunction()->hasFnAttribute(Attribute::MinSize));
 }
 
 bool ARMSubtarget::useFastISel() const {