[PATCH, i386, Pointer Bounds Checker 33/x] MPX ABI

[Ilya Enkovich]

2014-09-24 23:09 GMT+04:00 Jeff Law <law@redhat.com>:
> On 09/24/14 07:13, Ilya Enkovich wrote:
>>
>> I tried to generate PARALLEL with all regs set by call.  Here is a
>> memset call I got:
>>
>> (call_insn 23 22 24 2 (set (parallel [
>>                  (expr_list:REG_DEP_TRUE (reg:DI 0 ax)
>>                      (const_int 0 [0]))
>>                  (expr_list:REG_DEP_TRUE (reg:BND64 77 bnd0)
>>                      (const_int 0 [0]))
>>                  (expr_list:REG_DEP_TRUE (reg:BND64 78 bnd1)
>>                      (const_int 0 [0]))
>>              ])
>>          (call/j (mem:QI (symbol_ref:DI ("memset") [flags 0x41]
>
> [ snip ]
> Looks good.  This is the approved way to handle multiple results of a call.
>
>>
>> During register allocation LRA generated a weird move instruction:
>>
>> (insn 63 0 0 (set (reg/f:DI 100)
>>          (parallel [
>>                  (expr_list:REG_DEP_TRUE (reg:DI 0 ax)
>>                      (const_int 0 [0]))
>>                  (expr_list:REG_DEP_TRUE (reg:BND64 77 bnd0)
>>                      (const_int 0 [0]))
>>                  (expr_list:REG_DEP_TRUE (reg:BND64 78 bnd1)
>>                      (const_int 0 [0]))
>>              ])) -1
>>       (nil))
>>
>> Which caused ICE later in LRA.  This move happens because of
>> REG_RETURNED (reg/f:DI 100) (see condition in inherit_in_ebb at
>> lra-constraints.c:5312).  Thus this code in LRA doesn't accept
>> PARALLEL dest for calls.
>
> This is a bug in LRA then.  Multiple return values aren't heavily used, so
> I'm not surprised that its handling was missed in LRA.
>
> The question now is how to bundle things together in such a way as to make
> it easy for Vlad to reproduce and fix this in LRA.
>
> Jeff

I suppose it should be easy to reproduce using the same test case I
use and some speudo patch which adds fake return values (e.g. xmm6 and
xmm7) to calls.  Will try to make some minimal patch and test Vlad
could work with.

Ilya