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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233324 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index 77a8a7c51b31fa8dd1f7fb78f3d3a86408a8e710..3b1b8dd1b8ee4d0b6b49930c39197760cdba132d 100644 (file)
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/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());

diff --git a/test/CodeGen/ARM/struct_byval.ll b/test/CodeGen/ARM/struct_byval.ll
index 8a04e4d82b2f3ca04e8c7bc68e5cd9b5b3c98d2b..d7b9b477ec1efb9ed01f5420b25c1e337ca57a0f 100644 (file)
--- a/test/CodeGen/ARM/struct_byval.ll
+++ b/test/CodeGen/ARM/struct_byval.ll
@@ -1,5 +1,9 @@
 ; RUN: llc < %s -mtriple=armv7-apple-ios6.0 | FileCheck %s
 ; RUN: llc < %s -mtriple=thumbv7-apple-ios6.0 | FileCheck %s -check-prefix=THUMB
+; RUN: llc < %s -mtriple=armv7-unknown-nacl-gnueabi | FileCheck %s -check-prefix=NACL
+; RUN: llc < %s -mtriple=armv5-none-linux-gnueabi | FileCheck %s -check-prefix=NOMOVT
+
+; NOMOVT-NOT: movt
 
 ; rdar://9877866
 %struct.SmallStruct = type { i32, [8 x i32], [37 x i8] }
@@ -33,6 +37,14 @@ entry:
 ; THUMB: sub
 ; THUMB: str
 ; THUMB: bne
+; NACL-LABEL: g:
+; Ensure that use movw instead of constpool for the loop trip count. But don't
+; match the __stack_chk_guard movw
+; NACL: movw r{{[1-9]}}, #
+; NACL: ldr
+; NACL: sub
+; NACL: str
+; NACL: bne
   %st = alloca %struct.LargeStruct, align 4
   %call = call i32 @e2(%struct.LargeStruct* byval %st)
   ret i32 0
@@ -51,6 +63,11 @@ entry:
 ; THUMB: sub
 ; THUMB: vst1
 ; THUMB: bne
+; NACL: movw r{{[1-9]}}, #
+; NACL: vld1
+; NACL: sub
+; NACL: vst1
+; NACL: bne
   %st = alloca %struct.LargeStruct, align 16
   %call = call i32 @e3(%struct.LargeStruct* byval align 16 %st)
   ret i32 0