Windows ARM support

[basharast]

Hi,
I just want to know if it's possible to compile flycast libretro core for ARM32 (specifically for UWP)
Interpreter worked fine (partially because some games has textures issue) but it's almost stable
Dynarec was not possible because the arm32 code is for linux only if FEAT_SHREC = DYNAREC_JIT,
the only way I was able to compile is to activate the below options FEAT_SHREC = DYNAREC_CPP:

#if defined(TARGET_NO_JIT)
#define FEAT_SHREC DYNAREC_CPP
#define FEAT_AREC DYNAREC_NONE
#define FEAT_DSPREC DYNAREC_NONE
#endif

but I got black screen only (no crash happening)
I just need to know if there is any possible chance to get the dynarec working on UWP ARM32

Many thanks for your support.

[flyinghead]

I haven't looked at arm32 or arm64 on UWP at all so I don't know the extent of changes required to support them. I would think it's more complex than just setting some #define and certainly requires some additional code.

[Wunkolo]

Been trying to get a build going to get some scope for what it takes to do this.
There are some OS-specific things that have to be done around oslib.h and unwind_info.cpp and other such things now that there is a Windows-ARM platform to anticipate.

#ifdef _WIN64
#ifdef __MINGW64__
struct _RUNTIME_FUNCTION;
typedef struct _RUNTIME_FUNCTION RUNTIME_FUNCTION;
#else
+ #ifdef _M_ARM64 
+ struct _IMAGE_ARM64_RUNTIME_FUNCTION_ENTRY;
+ typedef struct _IMAGE_ARM64_RUNTIME_FUNCTION_ENTRY RUNTIME_FUNCTION;
+ #else
struct _IMAGE_RUNTIME_FUNCTION_ENTRY;
typedef struct _IMAGE_RUNTIME_FUNCTION_ENTRY RUNTIME_FUNCTION;
#endif
#endif
+ #endif

Because RUNTIME_FUNCTION is different on ARM64:

typedef struct _IMAGE_ARM64_RUNTIME_FUNCTION_ENTRY {
    DWORD BeginAddress;
    union {
        DWORD UnwindData;
        struct {
            DWORD Flag : 2;
            DWORD FunctionLength : 11;
            DWORD RegF : 3;
            DWORD RegI : 4;
            DWORD H : 1;
            DWORD CR : 2;
            DWORD FrameSize : 9;
        } DUMMYSTRUCTNAME;
    } DUMMYUNIONNAME;
} IMAGE_ARM64_RUNTIME_FUNCTION_ENTRY, * PIMAGE_ARM64_RUNTIME_FUNCTION_ENTRY;

some functions like UnwindInfo::end will have to be adjusted to some of these changes like the lack of EndAddress.

flycast/core/windows/unwind_info.cpp

Lines 67 to 88 in 85188bf

	size_t UnwindInfo::end(u32 offset, ptrdiff_t rwRxOffset)
	{
	u8 *endAddr = startAddr + offset;
	if ((uintptr_t)endAddr & 3)
	offset += 4 - ((uintptr_t)endAddr & 3);
	u8 *unwindInfo = startAddr + offset;
	memcpy(unwindInfo, &codes[0], codes.size() * sizeof(u16));
	RUNTIME_FUNCTION *table = (RUNTIME_FUNCTION *)(unwindInfo + codes.size() * sizeof(u16));
	table[0].BeginAddress = 0;
	table[0].EndAddress = (DWORD)(endAddr - startAddr);
	#ifndef __MINGW64__
	table[0].UnwindInfoAddress = (DWORD)(unwindInfo - startAddr);
	#else
	table[0].UnwindData = (DWORD)(unwindInfo - startAddr);
	#endif
	bool result = RtlAddFunctionTable(table, 1, (DWORD64)startAddr);
	tables.push_back(table);
	DEBUG_LOG(DYNAREC, "RtlAddFunctionTable %p sz %d rc %d tables: %d", startAddr, table[0].EndAddress, result, (u32)tables.size());
	return (unwindInfo + codes.size() * sizeof(u16) + sizeof(RUNTIME_FUNCTION)) - endAddr;
	}

[flyinghead]

Dynamic unwind information isn't absolutely needed to get a first build working. This is just needed to be able to throw exceptions through dynarec blocks. (There's no unwind info on arm32 for example.)

The main reason there's no build yet is that I don't have a hardware platform to test with.