[Win] Crash when enabling DFG JIT.

I'm getting some crashes when running with DFG enabled.

See bug 121001 for further details, the cause and type of fix are the same.

Created attachment 231070 [details]
Patch

[Geoffrey Garen]

Comment on attachment 231070 [details]
Patch

How does regT0, which is an enumerated constant, alias to void*?

I've tested the following code with MSVC which demonstrates the problem:

class A
{
public:
    A(int i) {}
};

void testfunc(void* p)
{
}

void testfunc(A a)
{
}

testfunc(0); // Invokes testfunc(void* p)
testfunc(1); // Invokes testfunc(A a)

When calling testfunc with 0, testfunc(void* p) is called.
When calling testfunc with 1, testfunc(A a) is called.

I'm not sure what the standard says here, it might be a compiler bug.
I assume GCC will call testfunc(A a) in both cases here.

[Geoffrey Garen]

Answering my own question, a RegisterID on x86 is an enumerated constant:

namespace X86Registers {
    typedef enum {
        eax,
        ecx,
        edx,
        ebx,
        esp,
        ebp,
        esi,
        edi,

#if CPU(X86_64)
        r8,
        r9,
        r10,
        r11,
        r12,
        r13,
        r14,
        r15,
#endif
    } RegisterID;

Can you test an enum? Do enumerated constants actually alias to void*?

Tried to replicate the actual code more accurately, and tested with an enum.

I got the same results, with argument regT0, testfunc(void* p) is called, and with argument regT1, testfunc(A a) is called.


namespace X86Registers {
    typedef enum {
        eax,
        ecx,
        edx,
        ebx,
        esp,
        ebp,
        esi,
        edi,
    } RegisterID;
}

typedef X86Registers::RegisterID GPRReg;

typedef X86Registers::RegisterID RegisterID;

static const GPRReg regT0 = X86Registers::eax;
static const GPRReg regT1 = X86Registers::edx;

class A
{
public:
    A(RegisterID i) {}
};

void testfunc(void* p)
{
}

void testfunc(A a)
{
}

testfunc(regT0); // Invokes testfunc(void* p)
testfunc(regT1); // Invokes testfunc(A a)

[Geoffrey Garen]

Comment on attachment 231070 [details]
Patch

r=me

It's kind of a shame that an enum aliases to void* -- that's pretty easy to get wrong.

Perhaps you can fix this in a follow-up patch by changing the void* inputs to ImmPtr inputs, or similar.

I think you should pursue a follow-up patch that changes void* input to

(In reply to comment #6)
> (From update of attachment 231070 [details])
> r=me
> 

Thanks!

> It's kind of a shame that an enum aliases to void* -- that's pretty easy to get wrong.
> 
> Perhaps you can fix this in a follow-up patch by changing the void* inputs to ImmPtr inputs, or similar.
> 
> I think you should pursue a follow-up patch that changes void* input to

Sounds good, I will look into that.

[WebKit Commit Bot]

Comment on attachment 231070 [details]
Patch

Clearing flags on attachment: 231070

Committed r168535: <http://trac.webkit.org/changeset/168535>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.