ARM-Darwin: keep the frame register reserved even if not updated.

Darwin platforms need the frame register to always point at a valid record even
if it's not updated in a leaf function. Backtraces are more important than one
extra GPR.

llvm-svn: 373738

llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp

@@ -191,7 +191,7 @@ getReservedRegs(const MachineFunction &MF) const {
   markSuperRegs(Reserved, ARM::PC);
   markSuperRegs(Reserved, ARM::FPSCR);
   markSuperRegs(Reserved, ARM::APSR_NZCV);
-  if (TFI->hasFP(MF))
+  if (TFI->hasFP(MF) || STI.isTargetDarwin())
     markSuperRegs(Reserved, getFramePointerReg(STI));
   if (hasBasePointer(MF))
     markSuperRegs(Reserved, BasePtr);

llvm/test/CodeGen/ARM/r7-fixed-darwin.ll

@@ -0,0 +1,15 @@
+; RUN: llc -mtriple=thumbv7k-apple-watchos %s -o - | FileCheck %s
+
+; r7 is FP on Darwin, and should be preserved even if we don't create a new
+; frame record for this leaf function. So make huge register pressure to try &
+; tempt LLVM to use it.
+define void @foo([16 x i32]* %ptr) {
+; CHECK-LABEL: foo:
+; CHECK: push.w
+; CHECK: .cfi_offset r7
+; CHECK-NOT: r7
+; CHECK: pop.w
+  %val = load volatile [16 x i32], [16 x i32]* %ptr
+  store volatile [16 x i32] %val, [16 x i32]* %ptr
+  ret void
+}

llvm/test/CodeGen/Thumb/long.ll

@@ -234,7 +234,7 @@ if.end:
   %c = add i64 %y, 47
   call void @f13(i64 %c)
 ; CHECK: adds
-; CHECK-NEXT: adcs
+; CHECK: adcs
 ; CHECK: bl
   ret void
 }

llvm/test/CodeGen/Thumb2/2010-03-15-AsmCCClobber.ll

@@ -17,7 +17,7 @@ target datalayout = "e-p:32:32:32-i1:8:32-i8:8:32-i16:16:32-i32:32:32-i64:32:32-
 ; CHECK: bl _f2
 ; CHECK: clz {{r[0-9]+}}
 ; CHECK-DAG: lsrs    {{r[0-9]+}}
-; CHECK-DAG: lsls    {{r[0-9]+}}
+; CHECK-DAG: lsl.w    {{r[0-9]+}}
 ; CHECK-NEXT: orr.w   {{r[0-9]+}}
 ; CHECK-NEXT: InlineAsm Start
 define void @test(%s1* %this, i32 %format, i32 %w, i32 %h, i32 %levels, i32* %s, i8* %data, i32* nocapture %rowbytes, void (i8*, i8*)* %release, i8* %info) nounwind {