glsl: Rework assignments with write_masks to have LHS chan count match RHS.
It turns out that most people new to this IR are surprised when an
assignment to (say) 3 components on the LHS takes 4 components on the
RHS. It also makes for quite strange IR output:
(assign (constant bool (1)) (x) (var_ref color) (swiz x (var_ref v) ))
(assign (constant bool (1)) (y) (var_ref color) (swiz yy (var_ref v) ))
(assign (constant bool (1)) (z) (var_ref color) (swiz zzz (var_ref v) ))
But even worse, even we get it wrong, as shown by this line of our
current step(float, vec4):
(assign (constant bool (1)) (w)
(var_ref t)
(expression float b2f (expression bool >=
(swiz w (var_ref x))(var_ref edge))))
where we try to assign a float to the writemasked-out x channel and
don't supply anything for the actual w channel we're writing. Drivers
right now just get lucky since ir_to_mesa spams the float value across
all the source channels of a vec4.
Instead, the RHS will now have a number of components equal to the
number of components actually being written. Hopefully this confuses
everyone less, and it also makes codegen for a scalar target simpler.
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
diff --git a/src/glsl/ir_constant_propagation.cpp b/src/glsl/ir_constant_propagation.cpp
index f7a0599f4..390f295 100644
--- a/src/glsl/ir_constant_propagation.cpp
+++ b/src/glsl/ir_constant_propagation.cpp
@@ -168,18 +168,26 @@
if (!found)
return;
+ int rhs_channel = 0;
+ for (int j = 0; j < 4; j++) {
+ if (j == channel)
+ break;
+ if (found->write_mask & (1 << j))
+ rhs_channel++;
+ }
+
switch (type->base_type) {
case GLSL_TYPE_FLOAT:
- data.f[i] = found->constant->value.f[channel];
+ data.f[i] = found->constant->value.f[rhs_channel];
break;
case GLSL_TYPE_INT:
- data.i[i] = found->constant->value.i[channel];
+ data.i[i] = found->constant->value.i[rhs_channel];
break;
case GLSL_TYPE_UINT:
- data.u[i] = found->constant->value.u[channel];
+ data.u[i] = found->constant->value.u[rhs_channel];
break;
case GLSL_TYPE_BOOL:
- data.b[i] = found->constant->value.b[channel];
+ data.b[i] = found->constant->value.b[rhs_channel];
break;
default:
assert(!"not reached");