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AMD Catalyst OpenCL ABI description

This chapter describes how kernel gets its argument, how access to constant data.

User data classes

User data is stored in first scalar registers. Data class indicates what data are stored. Following data classes:

• IMM_UAV - data to uav. Holds 4 registers. ApiSlot determines uavid.
• IMM_CONST_BUFFER - const buffer (4 registers). See below. ApiSlot determines const buffer id.
• PTR_UAV_TABLE - pointer to uav table (2 registers). Each entry holds 8 dwords. Count from zero. Table can be accessed by using SMRD (s_load_dwordxx) instructions.

Argument passing and kernel setup

First const buffer (id=0) holds:

• 0-2 dwords - global size for each dimensions
• 3 dword - number of dimensions
• 4-6 dwords - local size for each dimensions
• 8-10 dwords - number of groups for each dimensions
• 24-26 dwords - global offset for each dimensions
• 27 dword - get_global_offset(0)*(workDim>=1?get_global_offset(1):1)* (workDim==2?get_global_offset(2):1)
• 36-38 dwords (32-bit binary) - global offset for each dimensions
• 37-39 dwords (64-bit binary) - global offset for each dimensions

Second const buffer (id=1) holds:

arguments aligned to 4 dwords.

Other data and resources

Scalar register after userdata holds (n - userdatanum):

• s[n:n+2] - group id for each dimension

First three vector registers holds local ids for each dimensions.