TXA : Texture Virtual AA

SPA 5.0:
        {@{!}Pg}   TXA{.NDV}{.NODEP}{.phase}   Rd, Ra, #tsPtrIdxU13 {, #wmskU04}    {&req_6}   {&rdN}   {&wrN}   {?sched}   ;   
        {@{!}Pg}   TXA{.NDV}{.NODEP}{.phase}   Rd, Ra, #tidU08, #smpU05, #wmskU04   {&req_6}   {&rdN}   {&wrN}   {?sched}   ;   

  .NDV:    Forces the TEX to be considered non-divergent even though quad may be divergent.  
                   This will not promote inactive threads, only force it to be treated as non-divergent despite the fact
           that some threads might be inactive.  To activate disabled threads in a quad SAM must be used.
	   Only the active mask and shader type are used to determine if a quad of threads is divergent.

  .NODEP:  Indicates that there is no subsequent quad derivatives to be calculated.
	   Threads that have been "killed" will be disabled to stop unnecessary texture fetches.

  .phase:  Allows control on the current warps texture hash, used for scheduling.
               < NONE >
               .T - postfix increment of the 3 bit texture component of the hash.
	       .P - postfix increment of the 5 bit phase component, and zero out the 3 bit texture component of the hash. 



Immediate Inputs:

  #tsPtrIdxU13:
     This immediate index is used to fetch the packed header+sampler pointer entry from constant
     cache.  The bank from which it is fetched is determined by bundle state.The constant bank
     entry is 32 bit structure of the form "samplerPtr[31:20] | headerPtr[19:0]".
     In SetSamplerBinding.ViaHeaderBinding (i.e. OGL) mode, the headerPtr would be used as the
     samplerPtr as well. 
     Any header pointer greater than one specified in SetTexHeaderPoolC.MaximumIndex will be regarded
     as an "invalid" texture (i.e. equivalent to BIND_GROUP_TEXTURE_HEADER_VALID_FALSE in fermi).
     Any sampler pointer greater than one specified in SetSamplerHeaderPoolC.MaximumIndex will be
     regarded as an "invalid" texture (i.e. equivalent to BIND_GROUP_TEXTURE_HEADER_VALID_FALSE in
     fermi).

  #tidU08, #smpU05:
     This is the "almost" Fermi-compatible specification of tsPtrIdxU13 which allows running of
     legacy apps/traces where sass will transform these into tsPtrIdxU13 as follows:
     #tsPtrIdxU13 = {#smpU05, #tidU08}

  #wmskU04       destination write mask (decimated contiguous writes)
     Allows for write masking the returning data writes via a bit enable
     for each of R,G,B,A. A four-vector is always returned from TEX.
     #wmskU04 defaults to 0xf.

  Ra cannot be RZ.

  TXA implies a 2D normalized texture lookup.