TGSI Instruction Specification
==============================
==============================


1  Instruction Set Operations
=============================


1.1  GL_NV_vertex_program
-------------------------


1.1.1  ARL - Address Register Load

  dst.x = floor(src.x)
  dst.y = floor(src.y)
  dst.z = floor(src.z)
  dst.w = floor(src.w)


1.1.2  MOV - Move

  dst.x = src.x
  dst.y = src.y
  dst.z = src.z
  dst.w = src.w


1.1.3  LIT - Light Coefficients

  dst.x = 1.0
  dst.y = max(src.x, 0.0)
  dst.z = (src.x > 0.0) ? pow(max(src.y, 0.0), clamp(src.w, -128.0, 128.0)) : 0.0
  dst.w = 1.0


1.1.4  RCP - Reciprocal

  dst.x = 1.0 / src.x
  dst.y = 1.0 / src.x
  dst.z = 1.0 / src.x
  dst.w = 1.0 / src.x


1.1.5  RSQ - Reciprocal Square Root

  dst.x = 1.0 / sqrt(abs(src.x))
  dst.y = 1.0 / sqrt(abs(src.x))
  dst.z = 1.0 / sqrt(abs(src.x))
  dst.w = 1.0 / sqrt(abs(src.x))


1.1.6  EXP - Approximate Exponential Base 2

  dst.x = pow(2.0, floor(src.x))
  dst.y = src.x - floor(src.x)
  dst.z = pow(2.0, src.x)
  dst.w = 1.0


1.1.7  LOG - Approximate Logarithm Base 2

  dst.x = floor(lg2(abs(src.x)))
  dst.y = abs(src.x) / pow(2.0, floor(lg2(abs(src.x))))
  dst.z = lg2(abs(src.x))
  dst.w = 1.0


1.1.8  MUL - Multiply

  dst.x = src0.x * src1.x
  dst.y = src0.y * src1.y
  dst.z = src0.z * src1.z
  dst.w = src0.w * src1.w


1.1.9  ADD - Add

  dst.x = src0.x + src1.x
  dst.y = src0.y + src1.y
  dst.z = src0.z + src1.z
  dst.w = src0.w + src1.w


1.1.10  DP3 - 3-component Dot Product

  dst.x = src0.x * src1.x + src0.y * src1.y + src0.z * src1.z
  dst.y = src0.x * src1.x + src0.y * src1.y + src0.z * src1.z
  dst.z = src0.x * src1.x + src0.y * src1.y + src0.z * src1.z
  dst.w = src0.x * src1.x + src0.y * src1.y + src0.z * src1.z


1.1.11  DP4 - 4-component Dot Product

  dst.x = src0.x * src1.x + src0.y * src1.y + src0.z * src1.z + src0.w * src1.w
  dst.y = src0.x * src1.x + src0.y * src1.y + src0.z * src1.z + src0.w * src1.w
  dst.z = src0.x * src1.x + src0.y * src1.y + src0.z * src1.z + src0.w * src1.w
  dst.w = src0.x * src1.x + src0.y * src1.y + src0.z * src1.z + src0.w * src1.w


1.1.12  DST - Distance Vector

  dst.x = 1.0
  dst.y = src0.y * src1.y
  dst.z = src0.z
  dst.w = src1.w


1.1.13  MIN - Minimum

  dst.x = min(src0.x, src1.x)
  dst.y = min(src0.y, src1.y)
  dst.z = min(src0.z, src1.z)
  dst.w = min(src0.w, src1.w)


1.1.14  MAX - Maximum

  dst.x = max(src0.x, src1.x)
  dst.y = max(src0.y, src1.y)
  dst.z = max(src0.z, src1.z)
  dst.w = max(src0.w, src1.w)


1.1.15  SLT - Set On Less Than

  dst.x = (src0.x < src1.x) ? 1.0 : 0.0
  dst.y = (src0.y < src1.y) ? 1.0 : 0.0
  dst.z = (src0.z < src1.z) ? 1.0 : 0.0
  dst.w = (src0.w < src1.w) ? 1.0 : 0.0


1.1.16  SGE - Set On Greater Equal Than

  dst.x = (src0.x >= src1.x) ? 1.0 : 0.0
  dst.y = (src0.y >= src1.y) ? 1.0 : 0.0
  dst.z = (src0.z >= src1.z) ? 1.0 : 0.0
  dst.w = (src0.w >= src1.w) ? 1.0 : 0.0


1.1.17  MAD - Multiply And Add

  dst.x = src0.x * src1.x + src2.x
  dst.y = src0.y * src1.y + src2.y
  dst.z = src0.z * src1.z + src2.z
  dst.w = src0.w * src1.w + src2.w


1.2  GL_ATI_fragment_shader
---------------------------


1.2.1  SUB - Subtract

  dst.x = src0.x - src1.x
  dst.y = src0.y - src1.y
  dst.z = src0.z - src1.z
  dst.w = src0.w - src1.w


1.2.2  DOT3 - 3-component Dot Product

  Alias for DP3.


1.2.3  DOT4 - 4-component Dot Product

  Alias for DP4.


1.2.4  LERP - Linear Interpolate

  dst.x = src0.x * (src1.x - src2.x) + src2.x
  dst.y = src0.y * (src1.y - src2.y) + src2.y
  dst.z = src0.z * (src1.z - src2.z) + src2.z
  dst.w = src0.w * (src1.w - src2.w) + src2.w


1.2.5  CND - Condition

  dst.x = (src2.x > 0.5) ? src0.x : src1.x
  dst.y = (src2.y > 0.5) ? src0.y : src1.y
  dst.z = (src2.z > 0.5) ? src0.z : src1.z
  dst.w = (src2.w > 0.5) ? src0.w : src1.w


1.2.6  CND0 - Condition Zero

       Removed.  Use (CMP src2, src1, src0) instead.

1.2.7  DOT2ADD - 2-component Dot Product And Add

  dst.x = src0.x * src1.x + src0.y * src1.y + src2.x
  dst.y = src0.x * src1.x + src0.y * src1.y + src2.x
  dst.z = src0.x * src1.x + src0.y * src1.y + src2.x
  dst.w = src0.x * src1.x + src0.y * src1.y + src2.x


1.3  GL_EXT_vertex_shader
-------------------------


1.3.1  INDEX - Array Lookup

  Considered for removal from language.


1.3.2  NEGATE - Negate

  Considered for removal from language.


1.3.3  MADD - Multiply And Add

  Alias for MAD.


1.3.4  FRAC - Fraction

  dst.x = src.x - floor(src.x)
  dst.y = src.y - floor(src.y)
  dst.z = src.z - floor(src.z)
  dst.w = src.w - floor(src.w)


1.3.5  SETGE - Set On Greater Equal

  Alias for SGE.


1.3.6  SETLT - Set On Less Than

  Alias for SLT.


1.3.7  CLAMP - Clamp

  dst.x = clamp(src0.x, src1.x, src2.x)
  dst.y = clamp(src0.y, src1.y, src2.y)
  dst.z = clamp(src0.z, src1.z, src2.z)
  dst.w = clamp(src0.w, src1.w, src2.w)


1.3.8  FLOOR - Floor

  dst.x = floor(src.x)
  dst.y = floor(src.y)
  dst.z = floor(src.z)
  dst.w = floor(src.w)


1.3.9  ROUND - Round

  dst.x = round(src.x)
  dst.y = round(src.y)
  dst.z = round(src.z)
  dst.w = round(src.w)


1.3.10  EXPBASE2 - Exponential Base 2

  dst.x = pow(2.0, src.x)
  dst.y = pow(2.0, src.x)
  dst.z = pow(2.0, src.x)
  dst.w = pow(2.0, src.x)


1.3.11  LOGBASE2 - Logarithm Base 2

  dst.x = lg2(src.x)
  dst.y = lg2(src.x)
  dst.z = lg2(src.x)
  dst.w = lg2(src.x)


1.3.12  POWER - Power

  dst.x = pow(src0.x, src1.x)
  dst.y = pow(src0.x, src1.x)
  dst.z = pow(src0.x, src1.x)
  dst.w = pow(src0.x, src1.x)


1.3.13  RECIP - Reciprocal

  Alias for RCP.


1.3.14  RECIPSQRT - Reciprocal Square Root

  Alias for RSQ.


1.3.15  CROSSPRODUCT - Cross Product

  dst.x = src0.y * src1.z - src1.y * src0.z
  dst.y = src0.z * src1.x - src1.z * src0.x
  dst.z = src0.x * src1.y - src1.x * src0.y
  dst.w = 1.0


1.3.16  MULTIPLYMATRIX - Multiply Matrix

  Considered for removal from language.


1.4  GL_NV_vertex_program1_1
----------------------------


1.4.1  ABS - Absolute

  dst.x = abs(src.x)
  dst.y = abs(src.y)
  dst.z = abs(src.z)
  dst.w = abs(src.w)


1.4.2  RCC - Reciprocal Clamped

  dst.x = (1.0 / src.x) > 0.0 ? clamp(1.0 / src.x, 5.42101e-020, 1.884467e+019) : clamp(1.0 / src.x, -1.884467e+019, -5.42101e-020)
  dst.y = (1.0 / src.x) > 0.0 ? clamp(1.0 / src.x, 5.42101e-020, 1.884467e+019) : clamp(1.0 / src.x, -1.884467e+019, -5.42101e-020)
  dst.z = (1.0 / src.x) > 0.0 ? clamp(1.0 / src.x, 5.42101e-020, 1.884467e+019) : clamp(1.0 / src.x, -1.884467e+019, -5.42101e-020)
  dst.w = (1.0 / src.x) > 0.0 ? clamp(1.0 / src.x, 5.42101e-020, 1.884467e+019) : clamp(1.0 / src.x, -1.884467e+019, -5.42101e-020)


1.4.3  DPH - Homogeneous Dot Product

  dst.x = src0.x * src1.x + src0.y * src1.y + src0.z * src1.z + src1.w
  dst.y = src0.x * src1.x + src0.y * src1.y + src0.z * src1.z + src1.w
  dst.z = src0.x * src1.x + src0.y * src1.y + src0.z * src1.z + src1.w
  dst.w = src0.x * src1.x + src0.y * src1.y + src0.z * src1.z + src1.w


1.5  GL_NV_fragment_program
---------------------------


1.5.1  COS - Cosine

  dst.x = cos(src.x)
  dst.y = cos(src.x)
  dst.z = cos(src.x)
  dst.w = cos(src.w)


1.5.2  DDX - Derivative Relative To X

  dst.x = partialx(src.x)
  dst.y = partialx(src.y)
  dst.z = partialx(src.z)
  dst.w = partialx(src.w)


1.5.3  DDY - Derivative Relative To Y

  dst.x = partialy(src.x)
  dst.y = partialy(src.y)
  dst.z = partialy(src.z)
  dst.w = partialy(src.w)


1.5.4  EX2 - Exponential Base 2

  Alias for EXPBASE2.


1.5.5  FLR - Floor

  Alias for FLOOR.


1.5.6  FRC - Fraction

  Alias for FRAC.


1.5.7  KILP - Predicated Discard

  discard


1.5.8  LG2 - Logarithm Base 2

  Alias for LOGBASE2.


1.5.9  LRP - Linear Interpolate

  Alias for LERP.


1.5.10  PK2H - Pack Two 16-bit Floats

  TBD


1.5.11  PK2US - Pack Two Unsigned 16-bit Scalars

  TBD


1.5.12  PK4B - Pack Four Signed 8-bit Scalars

  TBD


1.5.13  PK4UB - Pack Four Unsigned 8-bit Scalars

  TBD


1.5.14  POW - Power

  Alias for POWER.


1.5.15  RFL - Reflection Vector

  dst.x = 2.0 * (src0.x * src1.x + src0.y * src1.y + src0.z * src1.z) / (src0.x * src0.x + src0.y * src0.y + src0.z * src0.z) * src0.x - src1.x
  dst.y = 2.0 * (src0.x * src1.x + src0.y * src1.y + src0.z * src1.z) / (src0.x * src0.x + src0.y * src0.y + src0.z * src0.z) * src0.y - src1.y
  dst.z = 2.0 * (src0.x * src1.x + src0.y * src1.y + src0.z * src1.z) / (src0.x * src0.x + src0.y * src0.y + src0.z * src0.z) * src0.z - src1.z
  dst.w = 1.0


1.5.16  SEQ - Set On Equal

  dst.x = (src0.x == src1.x) ? 1.0 : 0.0
  dst.y = (src0.y == src1.y) ? 1.0 : 0.0
  dst.z = (src0.z == src1.z) ? 1.0 : 0.0
  dst.w = (src0.w == src1.w) ? 1.0 : 0.0


1.5.17  SFL - Set On False

  dst.x = 0.0
  dst.y = 0.0
  dst.z = 0.0
  dst.w = 0.0


1.5.18  SGT - Set On Greater Than

  dst.x = (src0.x > src1.x) ? 1.0 : 0.0
  dst.y = (src0.y > src1.y) ? 1.0 : 0.0
  dst.z = (src0.z > src1.z) ? 1.0 : 0.0
  dst.w = (src0.w > src1.w) ? 1.0 : 0.0


1.5.19  SIN - Sine

  dst.x = sin(src.x)
  dst.y = sin(src.x)
  dst.z = sin(src.x)
  dst.w = sin(src.w)


1.5.20  SLE - Set On Less Equal Than

  dst.x = (src0.x <= src1.x) ? 1.0 : 0.0
  dst.y = (src0.y <= src1.y) ? 1.0 : 0.0
  dst.z = (src0.z <= src1.z) ? 1.0 : 0.0
  dst.w = (src0.w <= src1.w) ? 1.0 : 0.0


1.5.21  SNE - Set On Not Equal

  dst.x = (src0.x != src1.x) ? 1.0 : 0.0
  dst.y = (src0.y != src1.y) ? 1.0 : 0.0
  dst.z = (src0.z != src1.z) ? 1.0 : 0.0
  dst.w = (src0.w != src1.w) ? 1.0 : 0.0


1.5.22  STR - Set On True

  dst.x = 1.0
  dst.y = 1.0
  dst.z = 1.0
  dst.w = 1.0


1.5.23  TEX - Texture Lookup

  TBD


1.5.24  TXD - Texture Lookup with Derivatives

  TBD


1.5.25  TXP - Projective Texture Lookup

  TBD


1.5.26  UP2H - Unpack Two 16-Bit Floats

  TBD


1.5.27  UP2US - Unpack Two Unsigned 16-Bit Scalars

  TBD


1.5.28  UP4B - Unpack Four Signed 8-Bit Values

  TBD


1.5.29  UP4UB - Unpack Four Unsigned 8-Bit Scalars

  TBD


1.5.30  X2D - 2D Coordinate Transformation

  dst.x = src0.x + src1.x * src2.x + src1.y * src2.y
  dst.y = src0.y + src1.x * src2.z + src1.y * src2.w
  dst.z = src0.x + src1.x * src2.x + src1.y * src2.y
  dst.w = src0.y + src1.x * src2.z + src1.y * src2.w


1.6  GL_NV_vertex_program2
--------------------------


1.6.1  ARA - Address Register Add

  TBD


1.6.2  ARR - Address Register Load With Round

  dst.x = round(src.x)
  dst.y = round(src.y)
  dst.z = round(src.z)
  dst.w = round(src.w)


1.6.3  BRA - Branch

  pc = target


1.6.4  CAL - Subroutine Call

  push(pc)
  pc = target


1.6.5  RET - Subroutine Call Return

  pc = pop()


1.6.6  SSG - Set Sign

  dst.x = (src.x > 0.0) ? 1.0 : (src.x < 0.0) ? -1.0 : 0.0
  dst.y = (src.y > 0.0) ? 1.0 : (src.y < 0.0) ? -1.0 : 0.0
  dst.z = (src.z > 0.0) ? 1.0 : (src.z < 0.0) ? -1.0 : 0.0
  dst.w = (src.w > 0.0) ? 1.0 : (src.w < 0.0) ? -1.0 : 0.0


1.7  GL_ARB_vertex_program
--------------------------


1.7.1  SWZ - Extended Swizzle

  dst.x = src.x
  dst.y = src.y
  dst.z = src.z
  dst.w = src.w


1.7.2  XPD - Cross Product

  Alias for CROSSPRODUCT.


1.8  GL_ARB_fragment_program
----------------------------


1.8.1  CMP - Compare

  dst.x = (src0.x < 0.0) ? src1.x : src2.x
  dst.y = (src0.y < 0.0) ? src1.y : src2.y
  dst.z = (src0.z < 0.0) ? src1.z : src2.z
  dst.w = (src0.w < 0.0) ? src1.w : src2.w


1.8.2  KIL - Conditional Discard

  if (src.x < 0.0 || src.y < 0.0 || src.z < 0.0 || src.w < 0.0)
    discard
  endif


1.8.3  SCS - Sine Cosine

  dst.x = cos(src.x)
  dst.y = sin(src.x)
  dst.z = 0.0
  dst.y = 1.0


1.8.4  TXB - Texture Lookup With Bias

  TBD


1.9  GL_NV_fragment_program2
----------------------------


1.9.1  NRM - 3-component Vector Normalise

  dst.x = src.x / (src.x * src.x + src.y * src.y + src.z * src.z)
  dst.y = src.y / (src.x * src.x + src.y * src.y + src.z * src.z)
  dst.z = src.z / (src.x * src.x + src.y * src.y + src.z * src.z)
  dst.w = 1.0


1.9.2  DIV - Divide

  dst.x = src0.x / src1.x
  dst.y = src0.y / src1.y
  dst.z = src0.z / src1.z
  dst.w = src0.w / src1.w


1.9.3  DP2 - 2-component Dot Product

  dst.x = src0.x * src1.x + src0.y * src1.y
  dst.y = src0.x * src1.x + src0.y * src1.y
  dst.z = src0.x * src1.x + src0.y * src1.y
  dst.w = src0.x * src1.x + src0.y * src1.y


1.9.4  DP2A - 2-component Dot Product And Add

  Alias for DOT2ADD.


1.9.5  TXL - Texture Lookup With LOD

  TBD


1.9.6  BRK - Break

  TBD


1.9.7  IF - If

  TBD


1.9.8  BGNFOR - Begin a For-Loop

  dst.x = floor(src.x)
  dst.y = floor(src.y)
  dst.z = floor(src.z)

  if (dst.y <= 0)
    pc = [matching ENDFOR] + 1
  endif

  Note: The destination must be a loop register.
        The source must be a constant register.


1.9.9  REP - Repeat

  TBD


1.9.10  ELSE - Else

  TBD


1.9.11  ENDIF - End If

  TBD


1.9.12  ENDFOR - End a For-Loop

  dst.x = dst.x + dst.z
  dst.y = dst.y - 1.0

  if (dst.y > 0)
    pc = [matching BGNFOR instruction] + 1
  endif

  Note: The destination must be a loop register.


1.9.13  ENDREP - End Repeat

  TBD


1.10  GL_NV_vertex_program3
---------------------------


1.10.1  PUSHA - Push Address Register On Stack

  push(src.x)
  push(src.y)
  push(src.z)
  push(src.w)


1.10.2  POPA - Pop Address Register From Stack

  dst.w = pop()
  dst.z = pop()
  dst.y = pop()
  dst.x = pop()


1.11  GL_NV_gpu_program4
------------------------


1.11.1  CEIL - Ceiling

  dst.x = ceil(src.x)
  dst.y = ceil(src.y)
  dst.z = ceil(src.z)
  dst.w = ceil(src.w)


1.11.2  I2F - Integer To Float

  dst.x = (float) src.x
  dst.y = (float) src.y
  dst.z = (float) src.z
  dst.w = (float) src.w


1.11.3  NOT - Bitwise Not

  dst.x = ~src.x
  dst.y = ~src.y
  dst.z = ~src.z
  dst.w = ~src.w


1.11.4  TRUNC - Truncate

  dst.x = trunc(src.x)
  dst.y = trunc(src.y)
  dst.z = trunc(src.z)
  dst.w = trunc(src.w)


1.11.5  SHL - Shift Left

  dst.x = src0.x << src1.x
  dst.y = src0.y << src1.x
  dst.z = src0.z << src1.x
  dst.w = src0.w << src1.x


1.11.6  SHR - Shift Right

  dst.x = src0.x >> src1.x
  dst.y = src0.y >> src1.x
  dst.z = src0.z >> src1.x
  dst.w = src0.w >> src1.x


1.11.7  AND - Bitwise And

  dst.x = src0.x & src1.x
  dst.y = src0.y & src1.y
  dst.z = src0.z & src1.z
  dst.w = src0.w & src1.w


1.11.8  OR - Bitwise Or

  dst.x = src0.x | src1.x
  dst.y = src0.y | src1.y
  dst.z = src0.z | src1.z
  dst.w = src0.w | src1.w


1.11.9  MOD - Modulus

  dst.x = src0.x % src1.x
  dst.y = src0.y % src1.y
  dst.z = src0.z % src1.z
  dst.w = src0.w % src1.w


1.11.10  XOR - Bitwise Xor

  dst.x = src0.x ^ src1.x
  dst.y = src0.y ^ src1.y
  dst.z = src0.z ^ src1.z
  dst.w = src0.w ^ src1.w


1.11.11  SAD - Sum Of Absolute Differences

  dst.x = abs(src0.x - src1.x) + src2.x
  dst.y = abs(src0.y - src1.y) + src2.y
  dst.z = abs(src0.z - src1.z) + src2.z
  dst.w = abs(src0.w - src1.w) + src2.w


1.11.12  TXF - Texel Fetch

  TBD


1.11.13  TXQ - Texture Size Query

  TBD


1.11.14  CONT - Continue

  TBD


1.12  GL_NV_geometry_program4
-----------------------------


1.12.1  EMIT - Emit

  TBD


1.12.2  ENDPRIM - End Primitive

  TBD


1.13  GLSL
----------


1.13.1  BGNLOOP - Begin a Loop

  TBD


1.13.2  BGNSUB - Begin Subroutine

  TBD


1.13.3  ENDLOOP - End a Loop

  TBD


1.13.4  ENDSUB - End Subroutine

  TBD


1.13.5  INT - Truncate

  Alias for TRUNC.


1.13.6  NOISE1 - 1D Noise

  TBD


1.13.7  NOISE2 - 2D Noise

  TBD


1.13.8  NOISE3 - 3D Noise

  TBD


1.13.9  NOISE4 - 4D Noise

  TBD


1.13.10  NOP - No Operation

  Do nothing.


1.14  ps_1_1
------------


1.14.1  TEXKILL - Conditional Discard

  Alias for KIL.


1.15  ps_1_4
------------


1.15.1  TEXLD - Texture Lookup

  Alias for TEX.


1.16  ps_2_0
------------


1.16.1  M4X4 - Multiply Matrix

  Alias for MULTIPLYMATRIX.


1.16.2  M4X3 - Multiply Matrix

  Considered for removal from language.


1.16.3  M3X4 - Multiply Matrix

  Considered for removal from language.


1.16.4  M3X3 - Multiply Matrix

  Considered for removal from language.


1.16.5  M3X2 - Multiply Matrix

  Considered for removal from language.


1.16.6  CRS - Cross Product

  Alias for XPD.


1.16.7  NRM4 - 4-component Vector Normalise

  dst.x = src.x / (src.x * src.x + src.y * src.y + src.z * src.z + src.w * src.w)
  dst.y = src.y / (src.x * src.x + src.y * src.y + src.z * src.z + src.w * src.w)
  dst.z = src.z / (src.x * src.x + src.y * src.y + src.z * src.z + src.w * src.w)
  dst.w = src.w / (src.x * src.x + src.y * src.y + src.z * src.z + src.w * src.w)


1.16.8  SINCOS - Sine Cosine

  Alias for SCS.


1.16.9  TEXLDB - Texture Lookup With Bias

  Alias for TXB.


1.16.10  DP2ADD - 2-component Dot Product And Add

  Alias for DP2A.


1.17  ps_2_x
------------


1.17.1  CALL - Subroutine Call

  Alias for CAL.


1.17.2  CALLNZ - Subroutine Call If Not Zero

  TBD


1.17.3  IFC - If

  TBD


1.17.4  BREAK - Break

  Alias for BRK.


1.17.5  BREAKC - Break Conditional

  TBD


1.17.6  DSX - Derivative Relative To X

  Alias for DDX.


1.17.7  DSY - Derivative Relative To Y

  Alias for DDY.


1.17.8  TEXLDD - Texture Lookup with Derivatives

  Alias for TXD.


1.18  vs_1_1
------------


1.18.1  EXPP - Approximate Exponential Base 2

  Use EXP. See also 1.19.3.


1.18.2  LOGP - Logarithm Base 2

  Use LOG. See also 1.19.4.


1.19  vs_2_0
------------


1.19.1  SGN - Set Sign

  Alias for SSG.


1.19.2  MOVA - Move Address Register

  Alias for ARR.


1.19.3  EXPP - Approximate Exponential Base 2

  Use EX2.


1.19.4  LOGP - Logarithm Base 2

  Use LG2.


2  Explanation of symbols used
==============================


2.1  Functions
--------------


  abs(x)            Absolute value of x.
                    |x|
                    (x < 0.0) ? -x : x

  ceil(x)           Ceiling of x.

  clamp(x,y,z)      Clamp x between y and z.
                    (x < y) ? y : (x > z) ? z : x

  cos(x)            Cosine of x.

  floor(x)          Floor of x.

  lg2(x)            Logarithm base 2 of x.

  max(x,y)          Maximum of x and y.
                    (x > y) ? x : y

  min(x,y)          Minimum of x and y.
                    (x < y) ? x : y

  partialx(x)       Derivative of x relative to fragment's X.

  partialy(x)       Derivative of x relative to fragment's Y.

  pop()             Pop from stack.

  pow(x,y)          Raise x to power of y.

  push(x)           Push x on stack.

  round(x)          Round x.

  sin(x)            Sine of x.

  sqrt(x)           Square root of x.

  trunc(x)          Truncate x.


2.2  Keywords
-------------


  discard           Discard fragment.

  dst               First destination register.

  dst0              First destination register.

  pc                Program counter.

  src               First source register.

  src0              First source register.

  src1              Second source register.

  src2              Third source register.

  target            Label of target instruction.

