Hi,
I'd like to discuss 16-bit float and integer support in TGSI. I'm
proposing this:
struct tgsi_instruction
{
unsigned Type : 4; /* TGSI_TOKEN_TYPE_INSTRUCTION */
unsigned NrTokens : 8; /* UINT */
unsigned Opcode : 8; /* TGSI_OPCODE_ */
unsigned Saturate : 1; /* BOOL */
unsigned NumDstRegs : 2; /* UINT */
unsigned NumSrcRegs : 4; /* UINT */
unsigned Label : 1;
unsigned Texture : 1;
unsigned Memory : 1;
unsigned Precise : 1;
- unsigned Padding : 1;
+ unsigned HalfPrecision : 1;
};
There won't be any 16-bit TEMPs in TGSI, but each instruction will
have the HalfPrecision flag, which is a hint for drivers that they can
use a 16-bit opcode. Even texture, load, and store instructions can
set HalfPrecision, which means they can accept and return 16-bit
values.
The catch is that drivers will have to insert 16-bit <-> 32-bit
conversions manually, because they won't be present in TGSI. The
advantage is that we don't have to add 200 new opcodes for the 3 new
16-bit types.
What do you think?
Marek
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