Use movw/movt instead of constant pool loads to lower byval parameter copies

Summary:
The ARM backend can use a loop to implement copying byval parameters before
a call. In non-thumb2 mode it uses a constant pool load to materialize the
trip count. For targets that need movt instead (e.g. Native Client), use
the same code as in thumb2 mode to materialize the trip count.

Reviewers: jfb, t.p.northover

Differential Revision: http://reviews.llvm.org/D8442

llvm-svn: 233324

1 files changed, 9 insertions, 5 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 77a8a7c51b3..3b1b8dd1b8e 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -7105,16 +7105,20 @@ ARMTargetLowering::EmitStructByval(MachineInstr *MI,
 
   // Load an immediate to varEnd.
   unsigned varEnd = MRI.createVirtualRegister(TRC);
-  if (IsThumb2) {
+  if (Subtarget->useMovt(*MF)) {
     unsigned Vtmp = varEnd;
     if ((LoopSize & 0xFFFF0000) != 0)
       Vtmp = MRI.createVirtualRegister(TRC);
-    AddDefaultPred(BuildMI(BB, dl, TII->get(ARM::t2MOVi16), Vtmp)
-                       .addImm(LoopSize & 0xFFFF));
+    AddDefaultPred(BuildMI(BB, dl,
+                           TII->get(IsThumb2 ? ARM::t2MOVi16 : ARM::MOVi16),
+                           Vtmp).addImm(LoopSize & 0xFFFF));
 
     if ((LoopSize & 0xFFFF0000) != 0)
-      AddDefaultPred(BuildMI(BB, dl, TII->get(ARM::t2MOVTi16), varEnd)
-                         .addReg(Vtmp).addImm(LoopSize >> 16));
+      AddDefaultPred(BuildMI(BB, dl,
+                             TII->get(IsThumb2 ? ARM::t2MOVTi16 : ARM::MOVTi16),
+                             varEnd)
+                         .addReg(Vtmp)
+                         .addImm(LoopSize >> 16));
   } else {
     MachineConstantPool *ConstantPool = MF->getConstantPool();
     Type *Int32Ty = Type::getInt32Ty(MF->getFunction()->getContext());