On 3 November 2015 at 18:20, Matt Turner <matts...@gmail.com> wrote:
> On Tue, Nov 3, 2015 at 8:09 AM, Emil Velikov <emil.l.veli...@gmail.com> wrote:
>> On 3 November 2015 at 00:29, Matt Turner <matts...@gmail.com> wrote:
>>
>>> @@ -387,7 +342,9 @@ vec4_visitor::opt_vector_float()
>>>
>>> remaining_channels &= ~inst->dst.writemask;
>>> if (remaining_channels == 0) {
>>> - vec4_instruction *mov = MOV(inst->dst, imm);
>>> + unsigned vf;
>>> + memcpy(&vf, imm, sizeof(vf));
>>> + vec4_instruction *mov = MOV(inst->dst, brw_imm_vf(vf));
>> You can drop the temp variable + memcpy call and use brw_imm_vf4(imm[x],....)
>
> Ah, yes, I can. And it even generates identical code.
>
> Unfortunately, gcc isn't smart enough to understand that imm[] is not
> uninitialized. Wonder if it just doesn't warn about src arguments to
> memcpy()?
>
Actually it seems like a genuine warning.
if (inst->opcode != BRW_OPCODE_MOV ||
inst->dst.writemask == WRITEMASK_XYZW ||
inst->src[0].file != IMM)
continue;
int vf = brw_float_to_vf(inst->src[0].fixed_hw_reg.dw1.f);
if (vf == -1)
continue;
if ((inst->dst.writemask & WRITEMASK_X) != 0)
imm[0] = vf;
if ((inst->dst.writemask & WRITEMASK_Y) != 0)
imm[1] = vf;
if ((inst->dst.writemask & WRITEMASK_Z) != 0)
imm[2] = vf;
if ((inst->dst.writemask & WRITEMASK_W) != 0)
imm[3] = vf;
imm_inst[inst_count++] = inst;
remaining_channels &= ~inst->dst.writemask;
if (remaining_channels == 0) {
vec4_instruction *mov = MOV(inst->dst, imm);
mov->dst.type = BRW_REGISTER_TYPE_F;
mov->dst.writemask = WRITEMASK_XYZW;
From the above, if all the X Y Z and W writemasks are set, we just
jump to the next instruction. Thus, at least one of the imm values is
uninitialised. We might have found ourselves a bug :-)
-Emil
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