[ARM][Thumb][FIX] Add unwinding information to t4

[dnsampaio]

Summary

Add missing part of patch D71361. Now that the stack-frame
can be operated using a addw/subw instruction, they should
appear in the unwinding list.

[dmgreen]

Sounds good. Can you add a test?

[dnsampaio]

Added test

[dmgreen]

Thanks. LGTM

llvm/lib/Target/ARM/ARMAsmPrinter.cpp

if (SrcReg == ARM::SP) {
         MI->print(errs());
         llvm_unreachable("Unsupported opcode for unwinding information");
       case ARM::MOVr:
       case ARM::tMOVr:
         Offset = 0;
         break;
       case ARM::ADDri:
       case ARM::t2ADDri:
+      case ARM::t2ADDri12:
         Offset = -MI->getOperand(2).getImm();
         break;
       case ARM::SUBri:
       case ARM::t2SUBri:
+      case ARM::t2SUBri12:
         Offset = MI->getOperand(2).getImm();
         break;
       case ARM::tSUBspi:
         Offset = MI->getOperand(2).getImm()*4;
         break;
       case ARM::tADDspi:
       case ARM::tADDrSPi:
         Offset = -MI->getOperand(2).getImm()*4;

llvm/test/CodeGen/Thumb2/emit-unwinding.ll

 ; RUN: llc -mtriple thumbv7em-apple-unknown-eabi-macho %s -o - -O0 | FileCheck %s
 
 ; CHECK: add r7, sp, #{{[1-9]+}}
 
 define void @foo1() {
   call void asm sideeffect "", "~{r4}"()
   call void @foo2()
   ret void
 }
 
 declare void @foo2()
+
+; CHECK: _bar:
+; CHECK-NEXT: .cfi_startproc
+; CHECK-NEXT: @ %bb.0:
+; CHECK-NEXT: subw    sp, sp, #3800
+; CHECK-NEXT: .cfi_def_cfa_offset 3800
+; CHECK-NEXT: addw    sp, sp, #3800
+; CHECK-NEXT: bx      lr
+; CHECK-NEXT: .cfi_endproc
+
+define void @bar() {
+  %a1 = alloca [3800 x i8], align 4
+  %p = getelementptr inbounds [3800 x i8], [3800 x i8]* %a1, i32 0, i32 0
+  ret void
+}