I found the issue and fixed it.
The return value wasn't being put into the Rax register in
src/arch/x86/isa/decoder/two_byte_opcodes.isa
0x4: BasicOperate::gem5Op({{
uint64_t ret;
bool recognized = PseudoInst::pseudoInst<X86PseudoInstABI>(
xc->tcBase(), IMMEDIATE, ret);
if (!recognized)
fault = std::make_shared<InvalidOpcode>();
Rax = ret;
//<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<Added This
}}, IsNonSpeculative);
This code was simplified with the new abi stuff and the Rax = ret; must
have been lost in the shuffle.
I could push the fix to develop, or should I just make an issue on Jira?
Best,
Dan
On Mon, Nov 9, 2020 at 2:50 PM Daniel Gerzhoy <daniel.gerz...@gmail.com>
wrote:
> Let me further say that I know that the magic instructions are being
> called. I am just getting bogus return values.
>
> On Mon, Nov 9, 2020 at 2:18 PM Daniel Gerzhoy <daniel.gerz...@gmail.com>
> wrote:
>
>> Hi Matt,
>>
>> Thanks for this, it's very helpful. However after following the
>> instructions (I had to extrapolate a little because of the directory
>> structure changes you mentioned) I get the same result: Nill returns from
>> the magic instructions.
>> Actually It isn't nill, but a constant no matter what. If I compile my
>> program with -O0 its nill, if with -O2 its: 4198192, which is suspicious.
>>
>> To clarify, are these updated instructions specifically meant to fix
>> this issue I am running into? Or just general instructions to build m5op.o
>>
>> Here are the specific changes I made according to the link you provided,
>> the supplemental instructions, and extrapolating based on the directory
>> structure change.
>>
>> 1. In SConsopts I commented both:
>>
>> --- a/util/m5/src/abi/x86/SConsopts
>> +++ b/util/m5/src/abi/x86/SConsopts
>> @@ -27,8 +27,8 @@ Import('*')
>>
>> env['ABI'] = 'x86'
>> get_abi_opt('CROSS_COMPILE', '')
>> -env.Append(CXXFLAGS='-DM5OP_ADDR=0xFFFF0000')
>> -env.Append(CCFLAGS='-DM5OP_ADDR=0xFFFF0000')
>> +#env.Append(CXXFLAGS='-DM5OP_ADDR=0xFFFF0000')
>> +#env.Append(CCFLAGS='-DM5OP_ADDR=0xFFFF0000')
>>
>> env['CALL_TYPE']['inst'].impl('m5op.S', 'verify_inst.cc')
>> env['CALL_TYPE']['addr'].impl('m5op_addr.S', default=True)
>>
>> 2. In SConstruct I added:
>>
>> --- a/util/m5/SConstruct
>> +++ b/util/m5/SConstruct
>> @@ -44,7 +44,9 @@ def abspath(d):
>>
>> # Universal settings.
>> main.Append(CXXFLAGS=[ '-O2' ])
>> +main.Append(CXXFLAGS=[ '-std=c++11' ])
>> main.Append(CCFLAGS=[ '-O2' ])
>> main.Append(CPPPATH=[ common_include ])
>>
>> The compilation process compiles m5op.S with gcc though, so c++11 doesn't
>> have any effect on it. Not sure if that matters.
>>
>> 3. Finally I linked both m5_mmap.o and m5op.o as per the instructions but
>> I am a little wary of m5_mmap
>>
>> What does m5_mmap actually do if I don't have M5OP_ADDR defined. It looks
>> like nothing? Do I need to link it?
>>
>> *Is there something inside the program I need to do before calling magic
>> instructions that has to do with m5_mmap?*
>>
>> Thanks for your help,
>>
>> Dan
>>
>> On Mon, Nov 9, 2020 at 12:12 PM Matt Sinclair <mattdsincl...@gmail.com>
>> wrote:
>>
>>> Hi Dan,
>>>
>>> In recent weeks, Gabe (if I recall correctly) updated how the m5ops are
>>> created. I had created a homework assignment for my course about it:
>>> https://pages.cs.wisc.edu/~sinclair/courses/cs752/fall2020/handouts/hw3.html
>>> (see #2), but this is now already out of date as the location of some files
>>> changed. The updated instructions are:
>>>
>>> 1. Update $GEM5_ROOT/util/m5/SConstruct, add a new line between the
>>> current lines 46 and 47:
>>>
>>> main.Append(CXXFLAGS=[ '-O2' ])
>>> *+main.Append(CXXFLAGS=[ '-std=c++11' ])*
>>>
>>> main.Append(CCFLAGS=[ '-O2' ])
>>>
>>> 2. Now run the same command you ran in step 2 of the above link:
>>>
>>> scons build/x86/out/m5
>>>
>>> 3. This will create the same two .o files in step 2 of the above link,
>>> in the same places (although the location of m5op.o may have changed to
>>> include/gem5 util/m5/build/x86/abi/x86/ according to some of the
>>> students in my course).
>>> Matt
>>>
>>> On Mon, Nov 9, 2020 at 9:25 AM Daniel Gerzhoy via gem5-users <
>>> gem5-users@gem5.org> wrote:
>>>
>>>> Hey all,
>>>>
>>>> I've recently updated to using the dev branch for my GCN3 simulations.
>>>> I've noticed that I am now getting return values of 0 for every magic
>>>> instruction (m5_rpns for instance).
>>>>
>>>> Is there a special way I need to be compiling/linking m5ops.S to get
>>>> the return values to show up correctly? Or might this be a bug?
>>>>
>>>> Thanks,
>>>>
>>>> Dan
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>>>
>>>
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