D851 - An integer colour target takes the exported bits as they are

Status: decided Date: 2026-10-14

A draw tells the translator which of its pixel shader's colour targets hold integers (UserData::integer_targets, bit K for mrtK). Such a target's fragment output is a uvec4, not a vec4. An export to it stores its sources' bits as they are, not reinterpreted as floats. A compressed export to it stores its two 16-bit halves of each source as integers, not as halves. The draw's mask is part of the module's cache key.

Why: Vulkan requires a fragment output's component type to match its attachment's: a uvec4 for an unsigned-integer attachment. Mesa's ACO exports an integer target's value as the integer it is, packing two 16-bit integers into a register for a UINT16_ABGR export format (v_cvt_pk_u16_u32), where a float target's export is a float or two halves. Grand Theft Auto V draws into a 3840 x 2160 COLOR_16 NUMBER_UINT target.

Rejected:

• Converting each exported float to an integer: an integer target's export holds its integer bits, and converting them would change them.
• One output type for every target of a module: a pixel shader may write a float target and an integer one in the same draw.