Add float/double return value handling to SysV-arm ABI

[tberghammer]

Summary

Add float/double return value handling to SysV-arm ABI

This is necessary for evaluating expressions with float/double return
value and for displaying float/double return values in case of a thread
step out.

[labath]

LGTM, assuming this fixes an existing test. If not, please write a regression test.

source/Plugins/ABI/SysV-arm/ABISysV_arm.cpp

491

Please use reinterpret_cast here. Or use a union.

499

same here.

source/Plugins/ABI/SysV-arm/ABISysV_arm.cpp

ABISysV_arm::GetReturnValueObjectImpl (Thread &thread,
     //value.SetContext (Value::eContextTypeClangType, clang_type.GetOpaqueQualType());
     value.SetClangType (clang_type);
             
     RegisterContext *reg_ctx = thread.GetRegisterContext().get();
     if (!reg_ctx)
         return return_valobj_sp;
         
     bool is_signed;
+    bool is_complex;
+    uint32_t float_count;
     
     // Get the pointer to the first stack argument so we have a place to start 
     // when reading data
     
     const RegisterInfo *r0_reg_info = reg_ctx->GetRegisterInfo(eRegisterKindGeneric, LLDB_REGNUM_GENERIC_ARG1);
     if (clang_type.IsIntegerType (is_signed))
     {
         size_t bit_width = clang_type.GetBitSize(&thread);
if (clang_type.IsIntegerType (is_signed))
                 break;
         }
     }
     else if (clang_type.IsPointerType ())
     {
         uint32_t ptr = thread.GetRegisterContext()->ReadRegisterAsUnsigned(r0_reg_info, 0) & UINT32_MAX;
         value.GetScalar() = ptr;
     }
+    else if (clang_type.IsFloatingPointType(float_count, is_complex))
+    {
+        if (float_count == 1 && !is_complex)
+        {
+            size_t bit_width = clang_type.GetBitSize(&thread);
+            switch (bit_width)
+            {
+                default:
+                    return return_valobj_sp;
+                case 64:
+                {
+                    static_assert(sizeof(double) == sizeof(uint64_t), "");
+                    const RegisterInfo *r1_reg_info = reg_ctx->GetRegisterInfo(eRegisterKindGeneric, LLDB_REGNUM_GENERIC_ARG2);
+                    uint64_t raw_value;
+                    raw_value = reg_ctx->ReadRegisterAsUnsigned(r0_reg_info, 0) & UINT32_MAX;
+                    raw_value |= ((uint64_t)(reg_ctx->ReadRegisterAsUnsigned(r1_reg_info, 0) & UINT32_MAX)) << 32;
+                    value.GetScalar() = *(double*)&raw_value;
+                    break;
+                }
+                case 16: // Half precision returned after a conversion to single precision
+                case 32:
+                {
+                    static_assert(sizeof(float) == sizeof(uint32_t), "");
+                    uint32_t raw_value = reg_ctx->ReadRegisterAsUnsigned(r0_reg_info, 0) & UINT32_MAX;
+                    value.GetScalar() = *(float*)&raw_value;
+                    break;
+                }
+            }
+        }
+        else
+        {
+            // not handled yet
+            return return_valobj_sp;
+        }
+    }
     else
     {
         // not handled yet
         return return_valobj_sp;
     }
     
     // If we get here, we have a valid Value, so make our ValueObject out of it: