diff options
| author | Ian Romanick <[email protected]> | 2020-03-02 16:43:11 -0800 |
|---|---|---|
| committer | Marge Bot <[email protected]> | 2020-03-18 20:36:29 +0000 |
| commit | 325a21f5ebca90ccac9a7c3c571ed0513c4ec3d2 (patch) | |
| tree | df779843c312c67496067f373e4e737b4c9baf87 /src/compiler | |
| parent | 812230fd94e2661b1e69234f35f3ec0e3bcc9571 (diff) | |
soft-fp64: Simplify __countLeadingZeros32 function
findMSB returns -1 for an input of zero, so 31 - findMSB(a) is
sufficient on its own.
There's only one user of findMSB in shader-db, and it does not match
this pattern.
TODO: Add a pattern in the backend code generator that emits 31 -
nir_op_ufind_msb(a) as if it were nir_op_uclz. That should save a couple
instructions.
Results on the 308 shaders extracted from the fp64 portion of the OpenGL
CTS:
Tiger Lake and Ice Lake had similar results. (Tiger Lake shown)
total instructions in shared programs: 859509 -> 848109 (-1.33%)
instructions in affected programs: 841058 -> 829658 (-1.36%)
helped: 97
HURT: 0
helped stats (abs) min: 3 max: 1161 x̄: 117.53 x̃: 72
helped stats (rel) min: 0.98% max: 6.74% x̄: 1.70% x̃: 1.35%
95% mean confidence interval for instructions value: -147.21 -87.84
95% mean confidence interval for instructions %-change: -1.94% -1.46%
Instructions are helped.
total cycles in shared programs: 7072275 -> 6969145 (-1.46%)
cycles in affected programs: 6955767 -> 6852637 (-1.48%)
helped: 97
HURT: 0
helped stats (abs) min: 32 max: 10900 x̄: 1063.20 x̃: 560
helped stats (rel) min: 1.18% max: 7.58% x̄: 1.84% x̃: 1.45%
95% mean confidence interval for cycles value: -1339.43 -786.96
95% mean confidence interval for cycles %-change: -2.11% -1.57%
Cycles are helped.
Reviewed-by: Jason Ekstrand <[email protected]>
Reviewed-by: Matt Turner <[email protected]>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4142>
Diffstat (limited to 'src/compiler')
| -rw-r--r-- | src/compiler/glsl/float64.glsl | 4 |
1 files changed, 1 insertions, 3 deletions
diff --git a/src/compiler/glsl/float64.glsl b/src/compiler/glsl/float64.glsl index 9834241872c..f5dee00ae2b 100644 --- a/src/compiler/glsl/float64.glsl +++ b/src/compiler/glsl/float64.glsl @@ -537,9 +537,7 @@ __roundAndPackInt64(uint zSign, uint zFrac0, uint zFrac1, uint zFrac2) int __countLeadingZeros32(uint a) { - int shiftCount; - shiftCount = mix(31 - findMSB(a), 32, a == 0u); - return shiftCount; + return 31 - findMSB(a); } /* Takes an abstract floating-point value having sign `zSign', exponent `zExp', |