[aarch64-port-dev ] RFR: 8148783: aarch64: SEGV running SpecJBB2013

[Andrew Haley]

On 02/04/2016 04:46 PM, Edward Nevill wrote:
> 
> The webrev ensures this by using bits 32..47 from the PC and bits
> 0..31 from the destination address. The fact that we use the XXXX
> bits from the PC ensures the requirement that the address is
> reachable and using only the bottom 32 bits of the dest ensures we
> only get the bits we actually want the adrp instruction to construct
> and not any extraneous bits in bits 48 etc.
> 
> The code that does this is
> 
>    unsigned long adrp_target = (target & 0xffffffffUL) | (source & 0xffff00000000UL);
> 
> and this is also reflected in pd_patch_instruction to calculate the adrp target there.

Much better, but this still is confusing.  Surely you can do

    unsigned long target = (unsigned long)dest.target();
    unsigned long adrp_target
      = (target & 0xffffffffUL) | ((unsigned long)pc() & 0xffff00000000UL);

    _adrp(reg1, (address)adrp_target);
    movk(reg1, target >> 32, 32);
  }

"source" doesn't really mean anything here.

OK with that change.

Andrew.