4 ms·

Not having to worry about language feature support across different compilers is a big win. See https://bugs.chromium.org/p/libyuv/issues/detail?id=685 https:/

by dxf 9y ago

Not having to worry about language feature support across different compilers is a big win. See https://bugs.chromium.org/p/libyuv/issues/detail?id=685 https://bugs.chromium.org/p/libyuv/issues/detail?id=685 for one specific example of why using Clang can have benefits over MSVC (TL;DR: 64-bit MSVC doesn't support inline assembly). Clang was already being used to compile this little part of Chrome on Win64. Switching to Clang also allows the use of Clang-based sanitizers and fuzzing, which improves the security of Chrome.

blinkingled 9y ago
> 64-bit MSVC doesn't support inline assembly Wow. That's a big omission on Microsoft's part! I wonder how they themselves are getting around it for Win64 performance sensitive code.
- dman 9y ago
  You can still write routines in assembly, you cant write it inline.
  - MaulingMonkey 9y ago
    You can also use intrinsics if you don't want to write your entire routine in assembly.
  - yuhong 9y ago
    You are supposed to use special MASM directives to generate function tables for SEH.
- raverbashing 9y ago
  There are few reasons to use assembly, and even fewer to use inline assembly Using CPUID is one, using very specific vector instructions another (but you can do most of this using intrinsics) and it's better if they get their own .s file
- CoolGuySteve 9y ago
  IIRC, Microsoft wants you to use intrinsics because it plays better with their register coloring and code reordering optimizations. Unless there's an instruction you need that doesn't have an intrinsic or you're writing something like a spin lock where instruction ordering is critical and a compiler barrier for some reason is not sufficient, there's no reason to ever write assembly. Your code won't be appreciably faster than if you tuned it in the compiler, and after a few years the compiler will integrate new instructions while your assembly just gets stale.
  - xorblurb 9y ago
    > Unless there's an instruction you need that doesn't have an intrinsic or you're writing something like a spin lock where instruction ordering is critical and a compiler barrier for some reason is not sufficient, there's no reason to ever write assembly. So there are reasons to write code in assembly language.
    - CoolGuySteve 9y ago
      OK, there's no reason for YOU to write code in assembly.
      - xorblurb 9y ago
        For me, personally? I occasionally can write that kind of stuff.
- imron 9y ago
  inline assembly e.g. intermixed with C/C++ code is not supported. You can still have separate files that are ASM only. It's more hassle, but still possible to use.

by dxf 9y ago

blinkingled 9y ago

> 64-bit MSVC doesn't support inline assembly Wow. That's a big omission on Microsoft's part! I wonder how they themselves are getting around it for Win64 performance sensitive code.

dman 9y ago
You can still write routines in assembly, you cant write it inline.
- MaulingMonkey 9y ago
  You can also use intrinsics if you don't want to write your entire routine in assembly.
- yuhong 9y ago
  You are supposed to use special MASM directives to generate function tables for SEH.
raverbashing 9y ago
There are few reasons to use assembly, and even fewer to use inline assembly Using CPUID is one, using very specific vector instructions another (but you can do most of this using intrinsics) and it's better if they get their own .s file
CoolGuySteve 9y ago
IIRC, Microsoft wants you to use intrinsics because it plays better with their register coloring and code reordering optimizations. Unless there's an instruction you need that doesn't have an intrinsic or you're writing something like a spin lock where instruction ordering is critical and a compiler barrier for some reason is not sufficient, there's no reason to ever write assembly. Your code won't be appreciably faster than if you tuned it in the compiler, and after a few years the compiler will integrate new instructions while your assembly just gets stale.
- xorblurb 9y ago
  > Unless there's an instruction you need that doesn't have an intrinsic or you're writing something like a spin lock where instruction ordering is critical and a compiler barrier for some reason is not sufficient, there's no reason to ever write assembly. So there are reasons to write code in assembly language.
  - CoolGuySteve 9y ago
    OK, there's no reason for YOU to write code in assembly.
    - xorblurb 9y ago
      For me, personally? I occasionally can write that kind of stuff.
imron 9y ago
inline assembly e.g. intermixed with C/C++ code is not supported. You can still have separate files that are ASM only. It's more hassle, but still possible to use.