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authorPaul Berry <[email protected]>2013-10-15 20:44:00 -0700
committerPaul Berry <[email protected]>2013-10-24 22:00:57 -0700
commit1e3e72e3054de27b35322feb6c715e433b00be2a (patch)
tree138339d059877a06ce56568c3577cd1c62924ca0 /src/glsl/ir_clone.cpp
parent3c2feb1969db110523093740ace594b5c9d75a25 (diff)
i965: Reduce gl_MaxGeometryInputComponents to 64.
Although in principle there is no hardware limitation that prevents gl_MaxGeometryInputComponents from being set to 128 on Gen7, we have the following limitations in the vec4 compiler back end: - Registers assigned to geometry shader inputs can't be spilled or later re-used for any other purpose. - The last 16 registers are set aside for the "MRF hack", meaning they can only be used to send messages, and not for general purpose computation. - Up to 32 registers may be reserved for push constants, even if there is sufficient register pressure to make this impractical. A shader using 128 geometry input components, and having an input type of triangles_adjacency, would use up: - 1 register for r0 (which holds URB handles and various pieces of control information). - 1 register for gl_PrimitiveID. - 102 registers for geometry shader inputs (17 registers per input vertex, assuming DUAL_INSTANCED dispatch mode and allowing for one register of overhead for gl_Position and gl_PointSize, which are present in the URB map even if they are not used). - Up to 32 registers for push constants. - 16 registers for the "MRF hack". That's a total of 152 registers, which is well over the 128 registers the hardware supports. Fortunately, the GLSL 1.50 spec allows us to reduce gl_MaxGeometryInputComponents to 64. Doing that frees up 48 registers, brining the total down to 104 registers, leaving 24 registers available to do computation. Fixes piglit test spec/glsl-1.50/execution/geometry/max-input-components. Reviewed-by: Eric Anholt <[email protected]> Reviewed-by: Kenneth Graunke <[email protected]> Reviewed-by: Ian Romanick <[email protected]> Reviewed-by: Matt Turner <[email protected]>
Diffstat (limited to 'src/glsl/ir_clone.cpp')
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