In one branch we know that expDiff is already positive.
In the other branch we know the expDiff is negative. Previously in that
branch the code was -(expDiff + 1). This is equvialent to (-expDiff) -
1, and since expDiff is negative, abs(expDiff) - 1.
The main purpose of this commit is to prepare for "soft-fp64/fadd: Move
common code out of both branches of an if-statement".
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: 818246 -> 819560 (0.16%)
instructions in affected programs: 756423 -> 757737 (0.17%)
helped: 1
HURT: 73
helped stats (abs) min: 1205 max: 1205 x̄: 1205.00 x̃: 1205
helped stats (rel) min: 1.36% max: 1.36% x̄: 1.36% x̃: 1.36%
HURT stats (abs) min: 2 max: 149 x̄: 34.51 x̃: 27
HURT stats (rel) min: 0.14% max: 1.09% x̄: 0.41% x̃: 0.30%
95% mean confidence interval for instructions value: -16.56 52.07
95% mean confidence interval for instructions %-change: 0.30% 0.47%
Inconclusive result (value mean confidence interval includes 0).
total cycles in shared programs:
6816686 ->
6817254 (<.01%)
cycles in affected programs:
6384704 ->
6385272 (<.01%)
helped: 37
HURT: 37
helped stats (abs) min: 30 max: 5790 x̄: 289.05 x̃: 102
helped stats (rel) min: 0.04% max: 0.86% x̄: 0.29% x̃: 0.31%
HURT stats (abs) min: 2 max: 1020 x̄: 304.41 x̃: 232
HURT stats (rel) min: <.01% max: 1.58% x̄: 0.55% x̃: 0.43%
95% mean confidence interval for cycles value: -165.37 180.72
95% mean confidence interval for cycles %-change: <.01% 0.27%
Inconclusive result (value mean confidence interval includes 0).
total spills in shared programs: 705 -> 591 (-16.17%)
spills in affected programs: 705 -> 591 (-16.17%)
helped: 1
HURT: 0
total fills in shared programs: 1501 -> 1353 (-9.86%)
fills in affected programs: 1501 -> 1353 (-9.86%)
helped: 1
HURT: 0
Reviewed-by: Matt Turner <mattst88@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4142>
return mix(a, __propagateFloat64NaN(a, b), propagate);
}
- expDiff = mix(expDiff, expDiff - 1, bExp == 0);
+ expDiff = mix(abs(expDiff), abs(expDiff) - 1, bExp == 0);
bFracHi = mix(bFracHi | 0x00100000u, bFracHi, bExp == 0);
__shift64ExtraRightJamming(
bFracHi, bFracLo, 0u, expDiff, bFracHi, bFracLo, zFrac2);
bool propagate = (aFracHi | aFracLo) != 0u;
return mix(__packFloat64(aSign, 0x7ff, 0u, 0u), __propagateFloat64NaN(a, b), propagate);
}
- expDiff = mix(expDiff, expDiff + 1, bExp == 0);
+
+ expDiff = mix(abs(expDiff), abs(expDiff) - 1, bExp == 0);
bFracHi = mix(bFracHi | 0x00100000u, bFracHi, bExp == 0);
__shift64ExtraRightJamming(
- bFracHi, bFracLo, 0u, - expDiff, bFracHi, bFracLo, zFrac2);
+ bFracHi, bFracLo, 0u, expDiff, bFracHi, bFracLo, zFrac2);
zExp = aExp;
}