64 lines
3.6 KiB
Plaintext
64 lines
3.6 KiB
Plaintext
[video output=day114 member=cmuratori stream_platform=twitch stream_username=handmade_hero project=code title="Preparing a Function for Optimization" vod_platform=youtube id=_vkI9BedvKA annotator=dspecht annotator=Miblo]
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[1:31][Open things up and recap]
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[2:48][DrawRectangleSlowly: Increase efficiency]
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[3:33][Create DrawRectangleHopefullyQuickly]
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[4:34][DrawRectangleHopefullyQuickly: Skip the preamble]
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[5:42][Remove all unnecessary code]
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[6:44][Look at what's happening]
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[8:01][Make the edge testing code more explicit]
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[9:49][Blackboard: See what's happening with these inner products]
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[12:04][DrawRectangleHopefullyQuickly: Test U and V instead]
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[13:12][Run the game]
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[13:33][Make these U and V computations more efficient]
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[14:40][Run the game and ensure that everything still blits fine]
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[15:16][Continue pruning]
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[18:02][Flatten the routine]
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[19:55][Blow out v4 Blended into scalar form]
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[21:18][Take a close look at the routine and precompute InvTexelA]
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[23:35][Blow out v4 Dest and Texel into scalar form]
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[25:30][Flatten BilinearSample and SRGBBilinearBlend]
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[28:02][Assess our situation]
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[28:55][Unpack and optimise the Lerps]
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[33:57][Run the game and annotate the code]
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[35:33][Flatten SRGB255ToLinear1]
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[36:38][Flatten Unpack4x8]
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[38:59][That's everything flattened]
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[39:22][Note that the code is faster]
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[40:58][We have a nasty problem with the unpackings]
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[44:01][Blackboard: What is our "wide" strategy?]
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[48:43][Set the stage for SIMD]
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[50:45][Consider solidifying texture boundaries]
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[51:53][Leave it for today]
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[53:09][Q&A][:speech]
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[53:28][@braincruser][The way the code is written now you have a very long dependency chain (between instructions). Will you break down the code to remove it?]
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[56:42][@stelar7][Why did you write float instead of real32 this stream?]
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[57:14][@stelar7][Why use -O2 instead of -O3 or -Ofast (possibly with -fverbose-asm)?]
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[58:06][@garryjohanson][Do you ever use exclusive or operations to avoid pipeline stalls? If not, what do you use?]
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[59:04][@g3rain1][Aren't those square roots pretty expensive?[ref
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site="Intel"
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page="Intrinsics Guide"
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url="https://software.intel.com/sites/landingpage/IntrinsicsGuide/"]]
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[1:03:31][@andsz_][Will you make multiple SIMD backends? (SSE?/AVX/FMA versions)]
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[1:04:04][@davidthomas426][You could loft some of those variables out one more loop]
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[1:04:58][@waterlimon][How expensive is the float<>int conversion compared to the rest of the workload?[ref
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site="Intel"
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page="Intrinsics Guide"
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url="https://software.intel.com/sites/landingpage/IntrinsicsGuide/"]]
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[1:05:40][@davidthomas426][Since xAxis and yAxis are usually perpendicular, should we special case for that? In the same vein, should we special-case for axis-aligned?]
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[1:06:56][@waterlimon][Does the compiler do any automatic SSE optimization (or have option for it?)]
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[1:09:01][@stelar7][sqrt_ss vs sqrt_ps vs sqrt_pd?[ref
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site="Intel"
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page="Intrinsics Guide"
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url="https://software.intel.com/sites/landingpage/IntrinsicsGuide/"]]
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[1:11:56][@waterlimon][Would SSE allow doing sRGB using exponent 2.2 instead of approximating using one of 2, without a huge performance hit?]
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[1:12:41][@pseudonym73][The main reason why you don't get automatic SIMD is precise exceptions. You probably need to tell the compiler that you don't need them]
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[1:14:44][@waterlimon][What happens if "/arch:AVX2" switch is enabled?]
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[1:15:26][Look at this AVX-512 stuff[ref
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site="Intel"
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page="Intrinsics Guide"
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url="https://software.intel.com/sites/landingpage/IntrinsicsGuide/"]]
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[1:16:51][@braincruser][FMA is fused multiply add]
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[1:18:48][@andsz_][Yeah, looks like different caps bits]
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[1:19:23][Wrap things up][:speech]
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[/video]
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