Use MemoryMarshal.Cast<byte, _> on 64-bit Android #1606

AlanLiu90 · 2023-04-18T14:06:11Z

The original issue that SafeBitConverter tries to solve only happens on ARMv7 devices. But in current code, both 32-bit and 64-bit Android devices execute the non-efficient path.

This PR makes 64-bit Android can execute the efficent path. Due to the optimization of c++ compiler, if (sizeof(int*) == 4) and the unreachable branch will be eliminated, so they won't be in the compiled code.

AlanLiu90 · 2023-04-18T15:58:35Z

According to the documentation, Android is always little-endian, there is no need to check the endianness.

AlanLiu90 · 2023-04-19T21:37:52Z

Here is the comparison between ARMv7 and ARM64 code of the new implementation for SafeBitConverter.ToInt64 (Unity 2021.3.23f1 + IL2CPP with Release configuration):

ARMv7:

00743858 <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F>:
  743858:	e92d4ff0 	push	{r4, r5, r6, r7, r8, r9, sl, fp, lr}
  74385c:	e24dd004 	sub	sp, sp, #4
  743860:	e59f611c 	ldr	r6, [pc, #284]	; 743984 <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0x12c>
  743864:	e1a04000 	mov	r4, r0
  743868:	e1a05001 	mov	r5, r1
  74386c:	e08f6006 	add	r6, pc, r6
  743870:	e5d60000 	ldrb	r0, [r6]
  743874:	e3500000 	cmp	r0, #0
  743878:	1a000004 	bne	743890 <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0x38>
  74387c:	e59f0104 	ldr	r0, [pc, #260]	; 743988 <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0x130>
  743880:	e79f0000 	ldr	r0, [pc, r0]
  743884:	ebeb1109 	bl	207cb0 <_Z42il2cpp_codegen_initialize_runtime_metadataPj>
  743888:	e3a00001 	mov	r0, #1
  74388c:	e5c60000 	strb	r0, [r6]
  743890:	e3550000 	cmp	r5, #0
  743894:	0a000004 	beq	7438ac <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0x54>
  743898:	e5d40000 	ldrb	r0, [r4]
  74389c:	e3550001 	cmp	r5, #1
  7438a0:	1a000019 	bne	74390c <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0xb4>
  7438a4:	e1a05000 	mov	r5, r0
  7438a8:	ea000001 	b	7438b4 <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0x5c>
  7438ac:	ebeb1144 	bl	207dc4 <_Z49il2cpp_codegen_raise_index_out_of_range_exceptionv>
  7438b0:	e5d45000 	ldrb	r5, [r4]
  7438b4:	ebeb1142 	bl	207dc4 <_Z49il2cpp_codegen_raise_index_out_of_range_exceptionv>
  7438b8:	e5d49001 	ldrb	r9, [r4, #1]
  7438bc:	ebeb1140 	bl	207dc4 <_Z49il2cpp_codegen_raise_index_out_of_range_exceptionv>
  7438c0:	e5d4a002 	ldrb	sl, [r4, #2]
  7438c4:	ebeb113e 	bl	207dc4 <_Z49il2cpp_codegen_raise_index_out_of_range_exceptionv>
  7438c8:	e5d4b003 	ldrb	fp, [r4, #3]
  7438cc:	ebeb113c 	bl	207dc4 <_Z49il2cpp_codegen_raise_index_out_of_range_exceptionv>
  7438d0:	e5d46004 	ldrb	r6, [r4, #4]
  7438d4:	ebeb113a 	bl	207dc4 <_Z49il2cpp_codegen_raise_index_out_of_range_exceptionv>
  7438d8:	e5d47005 	ldrb	r7, [r4, #5]
  7438dc:	ebeb1138 	bl	207dc4 <_Z49il2cpp_codegen_raise_index_out_of_range_exceptionv>
  7438e0:	e5d48006 	ldrb	r8, [r4, #6]
  7438e4:	ebeb1136 	bl	207dc4 <_Z49il2cpp_codegen_raise_index_out_of_range_exceptionv>
  7438e8:	e5d41007 	ldrb	r1, [r4, #7]
  7438ec:	e1850409 	orr	r0, r5, r9, lsl #8
  7438f0:	e1862407 	orr	r2, r6, r7, lsl #8
  7438f4:	e180080a 	orr	r0, r0, sl, lsl #16
  7438f8:	e1822808 	orr	r2, r2, r8, lsl #16
  7438fc:	e1800c0b 	orr	r0, r0, fp, lsl #24
  743900:	e1821c01 	orr	r1, r2, r1, lsl #24
  743904:	e28dd004 	add	sp, sp, #4
  743908:	e8bd8ff0 	pop	{r4, r5, r6, r7, r8, r9, sl, fp, pc}
  74390c:	e5d49001 	ldrb	r9, [r4, #1]
  743910:	e3550002 	cmp	r5, #2
  743914:	9a000004 	bls	74392c <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0xd4>
  743918:	e5d4a002 	ldrb	sl, [r4, #2]
  74391c:	e3550003 	cmp	r5, #3
  743920:	1a000003 	bne	743934 <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0xdc>
  743924:	e1a05000 	mov	r5, r0
  743928:	eaffffe5 	b	7438c4 <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0x6c>
  74392c:	e1a05000 	mov	r5, r0
  743930:	eaffffe1 	b	7438bc <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0x64>
  743934:	e5d4b003 	ldrb	fp, [r4, #3]
  743938:	e3550004 	cmp	r5, #4
  74393c:	9a000004 	bls	743954 <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0xfc>
  743940:	e5d46004 	ldrb	r6, [r4, #4]
  743944:	e3550005 	cmp	r5, #5
  743948:	1a000003 	bne	74395c <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0x104>
  74394c:	e1a05000 	mov	r5, r0
  743950:	eaffffdf 	b	7438d4 <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0x7c>
  743954:	e1a05000 	mov	r5, r0
  743958:	eaffffdb 	b	7438cc <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0x74>
  74395c:	e5d47005 	ldrb	r7, [r4, #5]
  743960:	e3550006 	cmp	r5, #6
  743964:	9a000004 	bls	74397c <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0x124>
  743968:	e5d48006 	ldrb	r8, [r4, #6]
  74396c:	e3550007 	cmp	r5, #7
  743970:	e1a05000 	mov	r5, r0
  743974:	0affffda 	beq	7438e4 <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0x8c>
  743978:	eaffffda 	b	7438e8 <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0x90>
  74397c:	e1a05000 	mov	r5, r0
  743980:	eaffffd5 	b	7438dc <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0x84>
  743984:	00631d08 	.word	0x00631d08
  743988:	005e5650 	.word	0x005e5650

ARM64:

00000000007ece64 <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F>:
  7ece64:	f81d0ff6 	str	x22, [sp,#-48]!
  7ece68:	a90153f5 	stp	x21, x20, [sp,#16]
  7ece6c:	a9027bf3 	stp	x19, x30, [sp,#32]
  7ece70:	90003ad6 	adrp	x22, f44000 <GC_obj_kinds+0x40>
  7ece74:	f0003615 	adrp	x21, eaf000 <_GLOBAL_OFFSET_TABLE_+0x29d0>
  7ece78:	397d32c8 	ldrb	w8, [x22,#3916]
  7ece7c:	f941e2b5 	ldr	x21, [x21,#960]
  7ece80:	aa0103f3 	mov	x19, x1
  7ece84:	aa0003f4 	mov	x20, x0
  7ece88:	370000c8 	tbnz	w8, #0, 7ecea0 <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0x3c>
  7ece8c:	f0003600 	adrp	x0, eaf000 <_GLOBAL_OFFSET_TABLE_+0x29d0>
  7ece90:	f941e000 	ldr	x0, [x0,#960]
  7ece94:	97ed5f90 	bl	344cd4 <_Z42il2cpp_codegen_initialize_runtime_metadataPm>
  7ece98:	52800028 	mov	w8, #0x1                   	// #1
  7ece9c:	393d32c8 	strb	w8, [x22,#3916]
  7ecea0:	90003ad6 	adrp	x22, f44000 <GC_obj_kinds+0x40>
  7ecea4:	397d9ac8 	ldrb	w8, [x22,#3942]
  7ecea8:	f94002b5 	ldr	x21, [x21]
  7eceac:	35000128 	cbnz	w8, 7eced0 <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0x6c>
  7eceb0:	f0003600 	adrp	x0, eaf000 <_GLOBAL_OFFSET_TABLE_+0x29d0>
  7eceb4:	f941e000 	ldr	x0, [x0,#960]
  7eceb8:	97ed5f87 	bl	344cd4 <_Z42il2cpp_codegen_initialize_runtime_metadataPm>
  7ecebc:	b0003600 	adrp	x0, ead000 <_GLOBAL_OFFSET_TABLE_+0x9d0>
  7ecec0:	f944b800 	ldr	x0, [x0,#2416]
  7ecec4:	97ed5f84 	bl	344cd4 <_Z42il2cpp_codegen_initialize_runtime_metadataPm>
  7ecec8:	52800028 	mov	w8, #0x1                   	// #1
  7ececc:	393d9ac8 	strb	w8, [x22,#3942]
  7eced0:	f9401ea8 	ldr	x8, [x21,#56]
  7eced4:	aa1403e0 	mov	x0, x20
  7eced8:	aa1303e1 	mov	x1, x19
  7ecedc:	f9400d02 	ldr	x2, [x8,#24]
  7ecee0:	f9400448 	ldr	x8, [x2,#8]
  7ecee4:	d63f0100 	blr	x8
  7ecee8:	f27d727f 	tst	x19, #0xfffffff8
  7eceec:	540000c0 	b.eq	7ecf04 <SafeBitConverter_ToInt64_m9DE2E54118B3A6638F95C1F99E6B3DD3C64E375F+0xa0>
  7ecef0:	f9400000 	ldr	x0, [x0]
  7ecef4:	a9427bf3 	ldp	x19, x30, [sp,#32]
  7ecef8:	a94153f5 	ldp	x21, x20, [sp,#16]
  7ecefc:	f84307f6 	ldr	x22, [sp],#48
  7ecf00:	d65f03c0 	ret
  7ecf04:	97ed5fbb 	bl	344df0 <_Z49il2cpp_codegen_raise_index_out_of_range_exceptionv>

pCYSl5EDgo · 2024-01-30T15:23:55Z

@AlanLiu90 There is UNITY_64 scripting define symbols for 64 bit build.

#if UNITY_ANDROID && !UNITY_EDITOR && !UNITY_64

Isn't the above enough?

By the way, this PR will not to be merged because of #1734, I think.

AlanLiu90 · 2024-01-31T01:35:28Z

There is UNITY_64 scripting define symbols for 64 bit build.
#if UNITY_ANDROID && !UNITY_EDITOR && !UNITY_64
Isn't the above enough?

UNITY_64 doesn't work as expected on Android.

For the following code (Tested in Unity 2021.3.34 and with IL2CPP):

unsafe void Start()
{
#if UNITY_64
    Debug.Log($"sizeof(int*) is {sizeof(int*)} on 64-bit platform ({Application.platform})");
#else
    Debug.Log($"sizeof(int*) is {sizeof(int*)} on 32-bit platform ({Application.platform})");
#endif
}

On a 32-bit device, the Android player outputted: sizeof(int*) is 4 on 32-bit platform (Android)
On a 64-bit device, the Android player outputted: sizeof(int*) is 8 on 32-bit platform (Android)

AlanLiu90 added 2 commits April 18, 2023 21:58

Use MemoryMarshal.Cast<byte, _> on 64-bit Android

fb4a0c1

Remove the endianness check

010b236

Avoid executing the inefficient path in the Unity editor

fef02c0

AArnott requested a review from neuecc April 19, 2023 05:50

AArnott added the unity label Apr 19, 2023

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Use MemoryMarshal.Cast<byte, _> on 64-bit Android #1606

Use MemoryMarshal.Cast<byte, _> on 64-bit Android #1606

AlanLiu90 commented Apr 18, 2023 •

edited

AlanLiu90 commented Apr 18, 2023 •

edited

AlanLiu90 commented Apr 19, 2023 •

edited

pCYSl5EDgo commented Jan 30, 2024

AlanLiu90 commented Jan 31, 2024

Use MemoryMarshal.Cast<byte, _> on 64-bit Android #1606

Are you sure you want to change the base?

Use MemoryMarshal.Cast<byte, _> on 64-bit Android #1606

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AlanLiu90 commented Apr 18, 2023 • edited

AlanLiu90 commented Apr 18, 2023 • edited

AlanLiu90 commented Apr 19, 2023 • edited

pCYSl5EDgo commented Jan 30, 2024

AlanLiu90 commented Jan 31, 2024

AlanLiu90 commented Apr 18, 2023 •

edited

AlanLiu90 commented Apr 18, 2023 •

edited

AlanLiu90 commented Apr 19, 2023 •

edited