I'm running into a crash caused by mishandling of address calculation of an
array element address when that array is near the bottom of kseg0
(0xffffffff80000000).
The code essentially does this
foo = v[i - 2].elem;
where i is current zero.
Assume for now the negative array offset is valid -- data structure elements in
question exist to both sides of the label "v".
The generated code looks like this:
/* i is in v0 */
addiu v0, -2
sll v0, 3
lui v1, 0x8000
addu v0, v1
lbu a1, 7110(v0)
What's going on here is that &v[0].elem is 0xfffffffff80007110. The reference
is valid -- array elements are 8 bytes so element -2 is still in kseg0.
However, the addu produces value 0000000007ffffff0 in v0 -- the result of
adding -16 to the 32 bit value 0x800000000.
Given that I have an ABI with 64 bit registers -- even though it has 32 bit
pointers -- I would say the address adjustment should have been done with
daddu; if that had been done I would have gotten the correct address.
GCC is 4.5.1, NetBSD target.
paul
