2009/5/12 Stefan Dösinger stefan@codeweavers.com:
ps_1_3 uses Tx to pass in texture coordinates, but also as temporary registers. ps_1_4 and ps_2_0 only use them for texture coordinates. This patch gets rid of the Tx = fragment.texcoord[x] assign in all shader versions, and doesn't even declare Tx in ps_1_4 and ps_2_0.
The <=ps_1_3 instructions know which kind of input they expect from the Tx register, so the instruction handlers now know if they have to read the tempreg Tx or the varying fragment.texcoord[x]
I'm probably missing something obvious, but with pre-1.4 texcoord registers being read-write, what happens when you write to the register before using it to sample a texture?
I've put it in the backend and not the frontend because a hypothetical nvts shader backend would be confused by this.
Completely off-topic of course, but isn't it somewhat questionable to anthropomorphize source code?
Am Dienstag, 12. Mai 2009 21:17:10 schrieb Henri Verbeet:
I'm probably missing something obvious, but with pre-1.4 texcoord registers being read-write, what happens when you write to the register before using it to sample a texture?
Nothing special. However, you can't use it to sample afterwards, because you can't use a tex* instruction after a non-tex instruction. Ie:
ps_1_3 tex t0 mov t1, t0 tex t1 mov r0, t0
Z:\dev\shm\shader.txt(4,1): error X5055: Cannot use tex* instruction after non-tex* instruction.
With my patch, the mov will write to the temporary register form of t1; fragment.texcoord[1] will never be used in a correct shader. Now we don't enforce the tex-after-non-tex rule, but if we ever get such a shader enforcing this restriction is how to fix problems.
You cannot sample a Tx coord twice either:
ps_1_3 tex t0 tex t1 texbem t1, t0 mov r0, t1
Z:\dev\shm\shader.txt(4,1): error X5053: Tex register t1 already declared.
This even applies to texkill:
ps_1_3 tex t0 tex t1 texkill t1 mov r0, t0
Z:\dev\shm\shader.txt(4,1): error X5053: Tex register t1 already declared.
or
ps_1_3 texkill t0 tex t0 mov r0, t0
Z:\dev\shm\shader.txt(3,1): error X5053: Tex register t0 already declared.
If you want dependent reads in ps_1_3 and earlier, you have to use texreg2rgb:
ps_1_3 tex t0 texreg2rgb t1, t0 mov r0, t1
texreg2rgb knows that it should take the address from the tempreg form of t0, not fragment.texcoord[0]. You cannot use texreg2rgb to read from the texture coord:
ps_1_3 texreg2rgb t1, t0 mov r0, t1
Z:\dev\shm\shader.txt(2,1): error X5036: Read of uninitialized components(*) in t0: *r/0 *g/1 *b/2 *a/3
If you want to do that, you have to use texcrd:
ps_1_3 texcoord t0 texreg2rgb t1, t0 mov r0, t1
in which case texcoord to is a MOV_SAT t0, fragment.texcoord[0];
I've put it in the backend and not the frontend because a hypothetical nvts shader backend would be confused by this.
Completely off-topic of course, but isn't it somewhat questionable to anthropomorphize source code?
Maybe.
I had to make a decision where to put this register separation code, and I decided that this strange t0 register is valuable information on hardware/APIs that works the same way(ie, nvts, but not atifs), so implementing this register separation throws away information that may be important to such a shader implementation.
2009/5/12 Stefan Dösinger stefandoesinger@gmx.at:
Am Dienstag, 12. Mai 2009 21:17:10 schrieb Henri Verbeet:
I'm probably missing something obvious, but with pre-1.4 texcoord registers being read-write, what happens when you write to the register before using it to sample a texture?
Nothing special. However, you can't use it to sample afterwards, because you can't use a tex* instruction after a non-tex instruction. Ie:
Ok.
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Henri Verbeet -
Stefan Dösinger