metal-cpp: Objective-C vs C++

README.md

Summary

Shows differences in how code is generated when using metal-cpp (C++) vs Metal (Objective-C)

test.cpp

#include <Metal/Metal.hpp>

struct Foo {
    MTL::Texture *tex;

    ~Foo() {
        tex->release();
    }
};

/* Type your code here, or load an example. */
MTL::Texture *newTexture(Foo *p_foo, MTL::Device *p_dev, MTL::TextureDescriptor *p_desc) {
    MTL::Texture *tex = p_dev->newTexture(p_desc);

    p_foo->tex = tex->retain();

    return tex;
}

void foo_del(Foo *p_foo) {
    delete p_foo;
}

test.cpp.asm

; compiled with -std=c++17 -O3

newTexture(Foo*, MTL::Device*, MTL::TextureDescriptor*):
        stp     x20, x19, [sp, #-32]!
        stp     x29, x30, [sp, #16]
        add     x29, sp, #16
        mov     x8, x1
        mov     x19, x0
        adrp    x9, __ZN3MTL7Private8Selector28s_knewTextureWithDescriptor_E@GOTPAGE
        ldr     x9, [x9, __ZN3MTL7Private8Selector28s_knewTextureWithDescriptor_E@GOTPAGEOFF]
        ldr     x1, [x9]
        mov     x0, x8
        bl      _objc_msgSend
        mov     x20, x0
        adrp    x8, __ZN2NS7Private8Selector9s_kretainE@GOTPAGE
        ldr     x8, [x8, __ZN2NS7Private8Selector9s_kretainE@GOTPAGEOFF]
        ldr     x1, [x8]
        bl      _objc_msgSend
        str     x0, [x19]
        mov     x0, x20
        ldp     x29, x30, [sp, #16]
        ldp     x20, x19, [sp], #32
        ret

foo_del(Foo*):
        stp     x20, x19, [sp, #-32]!
        stp     x29, x30, [sp, #16]
        add     x29, sp, #16
        cbz     x0, LBB1_3
        mov     x19, x0
        ldr     x0, [x0]
        adrp    x8, __ZN2NS7Private8Selector10s_kreleaseE@GOTPAGE
        ldr     x8, [x8, __ZN2NS7Private8Selector10s_kreleaseE@GOTPAGEOFF]
        ldr     x1, [x8]
        bl      _objc_msgSend
        mov     x0, x19
        ldp     x29, x30, [sp, #16]
        ldp     x20, x19, [sp], #32
        b       operator delete(void*)
LBB1_3:
        ldp     x29, x30, [sp, #16]
        ldp     x20, x19, [sp], #32
        ret
        bl      ___clang_call_terminate

___clang_call_terminate:
        stp     x29, x30, [sp, #-16]!
        mov     x29, sp
        bl      ___cxa_begin_catch
        bl      std::terminate()

test.mm

#import <Metal/Metal.h>

struct Foo {
    id<MTLTexture> tex;
};

/* Type your code here, or load an example. */
id<MTLTexture> newTexture(Foo *p_foo, id<MTLDevice> p_dev, MTLTextureDescriptor *p_desc) {
    id<MTLTexture> tex = [p_dev newTextureWithDescriptor:p_desc];

    p_foo->tex = tex;

    return tex;
}

void foo_del(Foo *p_foo) {
    delete p_foo;
}

test.mm.asm

; compiled with -O3 -fobjc-arc

newTexture(Foo*, id<MTLDevice>, MTLTextureDescriptor*):
        stp     x22, x21, [sp, #-48]!
        stp     x20, x19, [sp, #16]
        stp     x29, x30, [sp, #32]
        add     x29, sp, #32
        mov     x21, x2
        mov     x20, x0
        mov     x0, x1
        bl      _objc_retain
        mov     x19, x0
        mov     x0, x21
        bl      _objc_retain
        mov     x21, x0
        mov     x0, x19
        mov     x2, x21
        bl      "_objc_msgSend$newTextureWithDescriptor:"
        mov     x22, x0
        mov     x0, x20
        mov     x1, x22
        bl      _objc_storeStrong
        mov     x0, x21
        bl      _objc_release
        mov     x0, x19
        bl      _objc_release
        mov     x0, x22
        ldp     x29, x30, [sp, #32]
        ldp     x20, x19, [sp, #16]
        ldp     x22, x21, [sp], #48
        b       _objc_autoreleaseReturnValue
        mov     x20, x0
        mov     x0, x21
        bl      _objc_release
        mov     x0, x19
        bl      _objc_release
        mov     x0, x20
        bl      __Unwind_Resume

foo_del(Foo*):
        cbz     x0, LBB1_2
        stp     x20, x19, [sp, #-32]!
        stp     x29, x30, [sp, #16]
        add     x29, sp, #16
        ldr     x8, [x0]
        mov     x19, x0
        mov     x0, x8
        bl      _objc_release
        mov     x0, x19
        ldp     x29, x30, [sp, #16]
        ldp     x20, x19, [sp], #32
        b       operator delete(void*)
LBB1_2:
        ret