This was probably disabled due to a combination of several bugs in the
generator code (fixed earlier in this series) and a misunderstanding
of the hardware spec. The documentation for most control flow
instructions mentions among other restrictions:
"Instruction compression is not allowed."
This however doesn't have any implications on 16 wide not being
supported, because none of the control flow instructions have
multi-register operands (control flow instructions are not compressed
on more recent hardware either, except maybe SNB's IF with inline
compare). In fact Gen4-5 had 16-wide control flow masks and stacks,
and the spec mentions in several places that control flow instructions
push and pop 16 channels worth of data -- Otherwise there doesn't seem
to be any indication that it shouldn't work.
Causes no piglit regressions, and gives the following shader-db
results on ILK:
total instructions in shared programs: 4711384 -> 4711384 (0.00%)
instructions in affected programs: 0 -> 0
helped: 0
HURT: 0
GAINED: 1215
LOST: 0
---
src/mesa/drivers/dri/i965/brw_fs_nir.cpp | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)
diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
index bd71404..5247738 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
@@ -417,18 +417,12 @@ fs_visitor::nir_emit_if(nir_if *if_stmt)
bld.emit(BRW_OPCODE_ENDIF);
- if (!try_replace_with_sel() && devinfo->gen < 6) {
- no16("Can't support (non-uniform) control flow on SIMD16\n");
- }
+ try_replace_with_sel();
}
void
fs_visitor::nir_emit_loop(nir_loop *loop)
{
- if (devinfo->gen < 6) {
- no16("Can't support (non-uniform) control flow on SIMD16\n");
- }
-
bld.emit(BRW_OPCODE_DO);
nir_emit_cf_list(&loop->body);
--
2.4.3
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