vkd3d/tests/hlsl/conditional.shader_test
Giovanni Mascellani 51f13391e6 vkd3d-shader/ir: Introduce a simple control flow graph structurizer.
The structurizer is implemented along the lines of what is usually called
the "structured program theorem": the control flow is completely
virtualized by mean of an additional TEMP register which stores the
block index which is currently running. The whole program is then
converted to a huge switch construction enclosed in a loop, executing
at each iteration the appropriate block and updating the register
depending on block jump instruction.

The algorithm's generality is also its major weakness: it accepts any
input program, even if its CFG is not reducible, but the output
program lacks any useful convergence information. It satisfies the
letter of the SPIR-V requirements, but it is expected that it will
be very inefficient to run on a GPU (unless a downstream compiler is
able to devirtualize the control flow and do a proper convergence
analysis pass). The algorithm is however very simple, and good enough
to at least pass tests, enabling further development. A better
alternative is expected to be upstreamed incrementally.

Side note: the structured program theorem is often called the
Böhm-Jacopini theorem; Böhm and Jacopini did indeed prove a variation
of it, but their algorithm is different from what is commontly attributed
to them and implemented here, so I opted for not using their name.
2024-02-06 23:07:07 +01:00

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[pixel shader todo(sm<4)]
uniform float4 u;
float4 main() : sv_target
{
if (u.x > 0.0)
return float4(0.1, 0.2, 0.3, 0.4);
else
return float4(0.9, 0.8, 0.7, 0.6);
}
[test]
uniform 0 float4 0.0 0.0 0.0 0.0
todo(sm<4) draw quad
probe all rgba (0.9, 0.8, 0.7, 0.6)
uniform 0 float4 0.1 0.0 0.0 0.0
todo(sm<4) draw quad
probe all rgba (0.1, 0.2, 0.3, 0.4)
[pixel shader todo(sm<4)]
uniform float4 u;
float4 main() : sv_target
{
[attr1]
if (u.x > 0.0)
return float4(0.1, 0.2, 0.3, 0.4);
else
return float4(0.9, 0.8, 0.7, 0.6);
}
[pixel shader todo(sm<4)]
uniform float4 u;
float4 main() : sv_target
{
[flatten]
if (u.x > 0.0)
return float4(0.1, 0.2, 0.3, 0.4);
else
return float4(0.9, 0.8, 0.7, 0.6);
}
[test]
uniform 0 float4 0.0 0.0 0.0 0.0
todo(sm<4) draw quad
probe all rgba (0.9, 0.8, 0.7, 0.6)
[pixel shader fail(sm<6)]
float4 u;
float main() : sv_target
{
[branch] [branch]
if (u.x > 0.0)
return float4(0.1, 0.2, 0.3, 0.4);
else
return float4(0.9, 0.8, 0.7, 0.6);
}
[pixel shader fail todo]
float4 u;
float main() : sv_target
{
[branch] [flatten]
if (u.x > 0.0)
return float4(0.1, 0.2, 0.3, 0.4);
else
return float4(0.9, 0.8, 0.7, 0.6);
}
% Using older profiles fails to compile with forced control flow instruction
[require]
shader model >= 3.0
[pixel shader todo(sm<4)]
uniform float4 u;
float4 main() : sv_target
{
[branch]
if (u.x > 0.0)
return float4(0.1, 0.2, 0.3, 0.4);
else
return float4(0.9, 0.8, 0.7, 0.6);
}
[test]
uniform 0 float4 0.0 0.0 0.0 0.0
todo(sm<4) draw quad
probe all rgba (0.9, 0.8, 0.7, 0.6)
[pixel shader]
float4 main() : sv_target
{
bool c = false;
float a = -1.0f;
if (c)
return float4(1.0, 2.0, 3.0, 4.0);
else if (a > 0)
return float4(5.0, 6.0, 7.0, 8.0);
else
return float4(9.0, 10.0, 11.0, 12.0);
}
[test]
draw quad
probe all rgba (9.0, 10.0, 11.0, 12.0)