armv8 NEON 如果条件 [英] armv8 NEON if condition

问题描述

我想在 armv8 NEON 内联汇编代码中实现 if 条件.在 armv7 中，这可以通过像这样检查溢出位来实现:

I would like to realize if condition in armv8 NEON inline assembly code. In armv7 this was possible through checking overflow bit like this:

  VMRS r4, FPSCR            
  BIC r4, r4, #(1<<27)      
  VMSR FPSCR, r4     

  vtst.16  d30, d30, d30    
  vqadd.u16  d30, d30, d30 

  vmrs r4, FPSCR            
  tst  r4, #(1<<27)         
  bne label1

但我无法在 armv8 等效代码中实现这一点.似乎 SQADD 不会影响 FPSR 中的溢出位，或者我无法像这样检查它.是否有可能或有更好的方法来跳过长代码部分?

But I am not able to achieve this in armv8 equivalent code. It seems that SQADD doesnt affect overflow bit in FPSR or I cannot check it like this. Is it possible or is there better approach how to skip long part of code?

谢谢

推荐答案

Aarch64 中提供了相同的信息.你只需要替换:

The same information is available in Aarch64. You just need to replace:

<代码>VMSR r4，FPSCRVMRS FPSCR, r4

作者:

<代码>MRS w4, FPSRMSR FPSR，w4

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