Re: [U-Boot] [PATCH 1/3] memcpy: use 32-bit copies if possible

Dear Joakim Tjernlund,

In message OF26FEA2CB.36E102EE-ONC1257649.0031301D-C1257649.0031EDAF@transmode.se you wrote:

...

How about:

  cl = 0;
  for (i=0; i<sizeof(long); ++i) {
     cl <<= 8;
     cl |= c & 0xff;
  }

GCC optimization will do the rest...

If you want gcc to optimise well, make it easy to do so. Changing the for loop into: for (i=sizeof(long); i; --i) makes it easier for gcc and more likely to result in optimal code.

Did you actually _check_ the code? (I did).

It does not matter. The generated code is identical.

What matters might be compiler options - "-Os" generates a small loop, and "-O3" and higher will unroll the loop, which is way more code.

Best regards,

Wolfgang Denk