Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
21 years ago

Unnecessary instructions

Hello, it's my first post. I have question about GCC generated code. We can find several unnecessary instructions. --- sample code --- unsigned short uh; uh = IORD_16DIRECT(base,ofst)...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
21 years ago

Don't use the IORD_16DIRECT ... it's a macro that expands to

the builtin function __builtin_ldhuio (see io.h). It's the builtin

that (apparently) adds the extra instruction.

If the extra instruction bothers you, you can always try something

like: 

#define CACHE_BYPASS(addr)       ((addr)|0x80000000)# define ADDR                                 0x09000024
...
  unsigned short uh = *(volatile unsigned short*)CACHE_BYPASS(ADDR);
  printf ("%04x\n",uh);

Regards,

--Scott