gcc generates bad code for volatile data

[Altera_Forum]

If you look at the generated code for reads of volatile char and short data, it seems that gcc assumes that the high bits of the register are undefined. 

 For instance: int fubar(volatile char *bar) { return *bar; }   Generates: ldbu r5, 0(r4) andi r3, r5, 255 xori r2, r3, 128 addi r2, r2, -128 ret   Without the volatile the expected 'ldb r2, 0(r4)' is generated.   I've tried buiding gcc with PROMOTE_MODE defined (to its typical value) - but that has no effect.   Any other thoughts??   David

[Altera_Forum]

Some further info: 

With 'volatile unsigned char *bar' both the 'ldbu' and 'andi rx,rx,0xff' instructions come from the 'zero_extendqisi2' pattern.   David