RFR 8191278: MappedByteBuffer bulk access memory failures are not handled gracefully

[Jamsheed]

Hi Dan,

updated webrev in place

added only assert

+  BasicType doing_unsafe_access_bt = T_BYTE;
+  assert((sizeof(bool) * CHAR_BIT) == 8, "not implemented");

Best regards,

Jamsheed

On 01/06/19 12:56 PM, Jamsheed wrote:
>
> Hi Dan,
>
> i understand it is incorrect to assume bool(cpp compiler) 
> implementation above byte level.
>
> in that case i will just put an assert.
>
> +  BasicType doing_unsafe_access_bt = T_BYTE;
>
> + assert(sizeof(bool) == 1, "not implemented");
>
> Best regards,
>
> Jamsheed
>
> On 31/05/19 10:34 PM, Jamsheed wrote:
>>> src/hotspot/share/opto/library_call.cpp
>>>     In src/hotspot/share/runtime/thread.hpp:
>>>     L1090:   volatile bool         _doing_unsafe_access;
>>>
>>>     L4220:   store_to_memory(control(), doing_unsafe_access_addr, 
>>> intcon(1), T_BYTE, Compile::AliasIdxRaw, MemNode::unordered);
>>>     L4230:   store_to_memory(control(), doing_unsafe_access_addr, 
>>> intcon(0), T_BYTE, Compile::AliasIdxRaw, MemNode::unordered);
>>>         Is T_BYTE a safe assumption (size wise) for writing to a C++ 
>>> bool?
>>
>> Thanks for pointing this.
>>
>> hope [1] will work ?
> [1]
> +  BasicType doing_unsafe_access_bt = T_BYTE;
> +  switch(sizeof(bool)) {
> +    case 1: doing_unsafe_access_bt = T_BYTE;  break;
> +    case 2: doing_unsafe_access_bt = T_SHORT; break;
> +    case 4: doing_unsafe_access_bt = T_INT;   break;
> +    case 8: doing_unsafe_access_bt = T_LONG;  break;
> +    default: ShouldNotReachHere();
> +  }
>
>    // update volatile field
> -  store_to_memory(control(), doing_unsafe_access_addr, intcon(1), 
> T_BYTE, Compile::AliasIdxRaw, MemNode::unordered);
> +  store_to_memory(control(), doing_unsafe_access_addr, intcon(1), 
> doing_unsafe_access_bt, Compile::AliasIdxRaw, MemNode::unordered);
>
>    // Call it.  Note that the length argument is not scaled.
>    make_runtime_call(RC_LEAF|RC_NO_FP,
>                      OptoRuntime::fast_arraycopy_Type(),
>                      StubRoutines::unsafe_arraycopy(),
>                      "unsafe_arraycopy",
>                      TypeRawPtr::BOTTOM,
>                      src, dst, size XTOP);
>
> -  store_to_memory(control(), doing_unsafe_access_addr, intcon(0), 
> T_BYTE, Compile::AliasIdxRaw, MemNode::unordered);
> +  store_to_memory(control(), doing_unsafe_access_addr, intcon(0), 
> doing_unsafe_access_bt, Compile::AliasIdxRaw, MemNode::unordered);