I tested with a shader that generates an ARL instruction and found
inst->dst is:
{file = PROGRAM_ADDRESS, index = 0, writemask = 1, cond_mask = 8, type
= 2, reladdr = 0x0}
in the code in question. I don't think there's any way that the dest
register's writemask could be set to zero.
Other instructions that don't use the dst register (like
OPCODE_BGNLOOP, OPCODE_IF, etc) use undef_dst to initialize the
instructions dst register.
BTW, the initialization of undef_dst seems incorrect:
static st_dst_reg undef_dst = st_dst_reg(PROGRAM_UNDEFINED,
SWIZZLE_NOOP, GLSL_TYPE_ERROR);
I think SWIZZLE_NOOP should be WRITEMASK_XYZW since the parameter is a
writemask, not a swizzle.
-Brian
On 10/09/2011 01:22 PM, Marek Olšák wrote:
Correct.
The thing was: even though we have an addressing register in TGSI
(e.g. tgsi_full_dst|src_register::Indirect), everybody except nv50 and
partially svga doesn't use it now. They expect the indirect register
file is always TGSI_FILE_ADDRESS and the index is 0, making the
destination of ARL irrelevant. This is probably a bug in those drivers
and that's what made me think that ARL doesn't need a destination
register. Sorry for the noise.
Marek
On Sun, Oct 9, 2011 at 8:51 PM, Bryan Cain<bryanca...@gmail.com> wrote:
What does it do if there's no destination register? In any case, I
don't think glsl_to_tgsi emits any ARLs of that form, so it shouldn't be
a problem.
Bryan
On 10/07/2011 01:06 PM, Marek Olšák wrote:
I think ARL is allowed to have no destination register, right? In that
case, there should be a special case not to eliminate ARLs.
Marek
On Fri, Oct 7, 2011 at 5:40 PM, Brian Paul<brian.e.p...@gmail.com> wrote:
From: Brian Paul<bri...@vmware.com>
This fixes a bug where we'd wind up emitting an invalid instruction like
MOVE R[0]., R[1]; - note the empty/zero writemask. If we don't write to
any dest register channels, cull the instruction.
---
src/mesa/state_tracker/st_glsl_to_tgsi.cpp | 8 +++++++-
1 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
index d8ef8a3..44b1149 100644
--- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
@@ -3776,8 +3776,14 @@ glsl_to_tgsi_visitor::eliminate_dead_code_advanced(void)
iter.remove();
delete inst;
removed++;
- } else
+ } else {
inst->dst.writemask&= ~(inst->dead_mask);
+ if (inst->dst.writemask == 0) {
+ iter.remove();
+ delete inst;
+ removed++;
+ }
+ }
}
ralloc_free(write_level);
--
1.7.3.4
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