existential_aggregate

An interface-typed *field* inside a struct (`Scene { IMat m; ... }`), with n implementations selected at runtime through a switch. Unlike `dynamic_dispatch` (a bare local existential), boxing the existential in an aggregate forces `legalizeExistentialTypeLayout` to float the existential field out and recompute the parent layout, and feeds specializeModule a witness-table-per-case blowup. Stresses specializeModule + legalizeExistentialTypeLayout + the downstream simplifyIR. Scales by breadth (number of implementations / switch cases). Scaling null: n scales cases, each an O(1) body; ideal specialization cost is O(n).

bucket: dynamic_dispatch · compile mode: target · flags: -target spirv -emit-spirv-directly · default N: 100

Phase composition across releases

Full sub-counter decomposition of compileInner — named leaf timers plus (self) residuals (a parent's time not covered by a named child, e.g. the autodiff transform in linkAndOptimizeIR (self)). Topmost band traces compileInner; hover a band for its phase.

Daily window progress

Overall compileInner: 80.4 → 78.1 ms -2.9% (2026-07-30 7c58a326b → 2026-08-29 28c755b09)

Contributors — the mutually-exclusive phase buckets (named leaves + (self) residuals) that tile compileInner; the pp column sums to the overall %. Buckets moving the total by ≥0.2% are listed, the rest fold into the remainder row. Below them, every other reported counter (nested/overlapping, e.g. serialized-module reads — own change only):

counter	Δ	own %	of total
linkAndOptimizeIR (self)	-1.1 ms	-12.3%	-1.3pp
generateOutput (self)	-0.7 ms	-5.1%	-0.9pp
SemanticChecking	+0.6 ms	+4.2%	+0.7pp
compileInner (self)	-0.3 ms	-73.2%	-0.4pp
generateIR	-0.3 ms	-4.4%	-0.4pp
legalizeExistentialTypeLayout	-0.3 ms	-19.0%	-0.4pp
legalizeResourceTypes	-0.2 ms	-22.2%	-0.3pp
simplifyIR	-0.2 ms	-1.6%	-0.2pp
(remaining 7 buckets)	+0.1 ms	–	+0.2pp

Largest day steps (≥5% of the previous day, both directions; bisect with git log <c0>..<c1> -- source/):

Reproduce

boundary	% vs prev day	commits	top buckets (own %)
none

Run from the slang repo root. This regenerates the sources below and re-runs this workload's measurement; --gen-dir keeps the generated files (they go to a tempdir and are deleted otherwise).

python3 tools/compile-perf/bench.py --slangc /path/to/slangc --only existential_aggregate --label repro --gen-dir repro-existential_aggregate

Compiled Slang source

existential_aggregate.slang (229 lines)

// AUTO-GENERATED by perf-suite/workloads.py - do not edit by hand.
RWStructuredBuffer<float> outBuf;

[anyValueSize(16)]
interface IMat { float shade(float x); }

struct M0 : IMat { float shade(float x) { return x * 1.0 + 0.0 + sin(x * 1.0); } }
struct M1 : IMat { float shade(float x) { return x * 2.0 + 1.0 + sin(x * 2.0); } }
struct M2 : IMat { float shade(float x) { return x * 3.0 + 2.0 + sin(x * 3.0); } }
struct M3 : IMat { float shade(float x) { return x * 4.0 + 3.0 + sin(x * 4.0); } }
struct M4 : IMat { float shade(float x) { return x * 5.0 + 4.0 + sin(x * 5.0); } }
struct M5 : IMat { float shade(float x) { return x * 6.0 + 5.0 + sin(x * 6.0); } }
struct M6 : IMat { float shade(float x) { return x * 7.0 + 6.0 + sin(x * 7.0); } }
struct M7 : IMat { float shade(float x) { return x * 8.0 + 7.0 + sin(x * 1.0); } }
struct M8 : IMat { float shade(float x) { return x * 9.0 + 8.0 + sin(x * 2.0); } }
struct M9 : IMat { float shade(float x) { return x * 10.0 + 9.0 + sin(x * 3.0); } }
struct M10 : IMat { float shade(float x) { return x * 11.0 + 10.0 + sin(x * 4.0); } }
struct M11 : IMat { float shade(float x) { return x * 12.0 + 11.0 + sin(x * 5.0); } }
struct M12 : IMat { float shade(float x) { return x * 13.0 + 12.0 + sin(x * 6.0); } }
struct M13 : IMat { float shade(float x) { return x * 14.0 + 13.0 + sin(x * 7.0); } }
struct M14 : IMat { float shade(float x) { return x * 15.0 + 14.0 + sin(x * 1.0); } }
struct M15 : IMat { float shade(float x) { return x * 16.0 + 15.0 + sin(x * 2.0); } }
struct M16 : IMat { float shade(float x) { return x * 17.0 + 16.0 + sin(x * 3.0); } }
struct M17 : IMat { float shade(float x) { return x * 18.0 + 17.0 + sin(x * 4.0); } }
struct M18 : IMat { float shade(float x) { return x * 19.0 + 18.0 + sin(x * 5.0); } }
struct M19 : IMat { float shade(float x) { return x * 20.0 + 19.0 + sin(x * 6.0); } }
struct M20 : IMat { float shade(float x) { return x * 21.0 + 20.0 + sin(x * 7.0); } }
struct M21 : IMat { float shade(float x) { return x * 22.0 + 21.0 + sin(x * 1.0); } }
struct M22 : IMat { float shade(float x) { return x * 23.0 + 22.0 + sin(x * 2.0); } }
struct M23 : IMat { float shade(float x) { return x * 24.0 + 23.0 + sin(x * 3.0); } }
struct M24 : IMat { float shade(float x) { return x * 25.0 + 24.0 + sin(x * 4.0); } }
struct M25 : IMat { float shade(float x) { return x * 26.0 + 25.0 + sin(x * 5.0); } }
struct M26 : IMat { float shade(float x) { return x * 27.0 + 26.0 + sin(x * 6.0); } }
struct M27 : IMat { float shade(float x) { return x * 28.0 + 27.0 + sin(x * 7.0); } }
struct M28 : IMat { float shade(float x) { return x * 29.0 + 28.0 + sin(x * 1.0); } }
struct M29 : IMat { float shade(float x) { return x * 30.0 + 29.0 + sin(x * 2.0); } }
struct M30 : IMat { float shade(float x) { return x * 31.0 + 30.0 + sin(x * 3.0); } }
struct M31 : IMat { float shade(float x) { return x * 32.0 + 31.0 + sin(x * 4.0); } }
struct M32 : IMat { float shade(float x) { return x * 33.0 + 32.0 + sin(x * 5.0); } }
struct M33 : IMat { float shade(float x) { return x * 34.0 + 33.0 + sin(x * 6.0); } }
struct M34 : IMat { float shade(float x) { return x * 35.0 + 34.0 + sin(x * 7.0); } }
struct M35 : IMat { float shade(float x) { return x * 36.0 + 35.0 + sin(x * 1.0); } }
struct M36 : IMat { float shade(float x) { return x * 37.0 + 36.0 + sin(x * 2.0); } }
struct M37 : IMat { float shade(float x) { return x * 38.0 + 37.0 + sin(x * 3.0); } }
struct M38 : IMat { float shade(float x) { return x * 39.0 + 38.0 + sin(x * 4.0); } }
struct M39 : IMat { float shade(float x) { return x * 40.0 + 39.0 + sin(x * 5.0); } }
struct M40 : IMat { float shade(float x) { return x * 41.0 + 40.0 + sin(x * 6.0); } }
struct M41 : IMat { float shade(float x) { return x * 42.0 + 41.0 + sin(x * 7.0); } }
struct M42 : IMat { float shade(float x) { return x * 43.0 + 42.0 + sin(x * 1.0); } }
struct M43 : IMat { float shade(float x) { return x * 44.0 + 43.0 + sin(x * 2.0); } }
struct M44 : IMat { float shade(float x) { return x * 45.0 + 44.0 + sin(x * 3.0); } }
struct M45 : IMat { float shade(float x) { return x * 46.0 + 45.0 + sin(x * 4.0); } }
struct M46 : IMat { float shade(float x) { return x * 47.0 + 46.0 + sin(x * 5.0); } }
struct M47 : IMat { float shade(float x) { return x * 48.0 + 47.0 + sin(x * 6.0); } }
struct M48 : IMat { float shade(float x) { return x * 49.0 + 48.0 + sin(x * 7.0); } }
struct M49 : IMat { float shade(float x) { return x * 50.0 + 49.0 + sin(x * 1.0); } }
struct M50 : IMat { float shade(float x) { return x * 51.0 + 50.0 + sin(x * 2.0); } }
struct M51 : IMat { float shade(float x) { return x * 52.0 + 51.0 + sin(x * 3.0); } }
struct M52 : IMat { float shade(float x) { return x * 53.0 + 52.0 + sin(x * 4.0); } }
struct M53 : IMat { float shade(float x) { return x * 54.0 + 53.0 + sin(x * 5.0); } }
struct M54 : IMat { float shade(float x) { return x * 55.0 + 54.0 + sin(x * 6.0); } }
struct M55 : IMat { float shade(float x) { return x * 56.0 + 55.0 + sin(x * 7.0); } }
struct M56 : IMat { float shade(float x) { return x * 57.0 + 56.0 + sin(x * 1.0); } }
struct M57 : IMat { float shade(float x) { return x * 58.0 + 57.0 + sin(x * 2.0); } }
struct M58 : IMat { float shade(float x) { return x * 59.0 + 58.0 + sin(x * 3.0); } }
struct M59 : IMat { float shade(float x) { return x * 60.0 + 59.0 + sin(x * 4.0); } }
struct M60 : IMat { float shade(float x) { return x * 61.0 + 60.0 + sin(x * 5.0); } }
struct M61 : IMat { float shade(float x) { return x * 62.0 + 61.0 + sin(x * 6.0); } }
struct M62 : IMat { float shade(float x) { return x * 63.0 + 62.0 + sin(x * 7.0); } }
struct M63 : IMat { float shade(float x) { return x * 64.0 + 63.0 + sin(x * 1.0); } }
struct M64 : IMat { float shade(float x) { return x * 65.0 + 64.0 + sin(x * 2.0); } }
struct M65 : IMat { float shade(float x) { return x * 66.0 + 65.0 + sin(x * 3.0); } }
struct M66 : IMat { float shade(float x) { return x * 67.0 + 66.0 + sin(x * 4.0); } }
struct M67 : IMat { float shade(float x) { return x * 68.0 + 67.0 + sin(x * 5.0); } }
struct M68 : IMat { float shade(float x) { return x * 69.0 + 68.0 + sin(x * 6.0); } }
struct M69 : IMat { float shade(float x) { return x * 70.0 + 69.0 + sin(x * 7.0); } }
struct M70 : IMat { float shade(float x) { return x * 71.0 + 70.0 + sin(x * 1.0); } }
struct M71 : IMat { float shade(float x) { return x * 72.0 + 71.0 + sin(x * 2.0); } }
struct M72 : IMat { float shade(float x) { return x * 73.0 + 72.0 + sin(x * 3.0); } }
struct M73 : IMat { float shade(float x) { return x * 74.0 + 73.0 + sin(x * 4.0); } }
struct M74 : IMat { float shade(float x) { return x * 75.0 + 74.0 + sin(x * 5.0); } }
struct M75 : IMat { float shade(float x) { return x * 76.0 + 75.0 + sin(x * 6.0); } }
struct M76 : IMat { float shade(float x) { return x * 77.0 + 76.0 + sin(x * 7.0); } }
struct M77 : IMat { float shade(float x) { return x * 78.0 + 77.0 + sin(x * 1.0); } }
struct M78 : IMat { float shade(float x) { return x * 79.0 + 78.0 + sin(x * 2.0); } }
struct M79 : IMat { float shade(float x) { return x * 80.0 + 79.0 + sin(x * 3.0); } }
struct M80 : IMat { float shade(float x) { return x * 81.0 + 80.0 + sin(x * 4.0); } }
struct M81 : IMat { float shade(float x) { return x * 82.0 + 81.0 + sin(x * 5.0); } }
struct M82 : IMat { float shade(float x) { return x * 83.0 + 82.0 + sin(x * 6.0); } }
struct M83 : IMat { float shade(float x) { return x * 84.0 + 83.0 + sin(x * 7.0); } }
struct M84 : IMat { float shade(float x) { return x * 85.0 + 84.0 + sin(x * 1.0); } }
struct M85 : IMat { float shade(float x) { return x * 86.0 + 85.0 + sin(x * 2.0); } }
struct M86 : IMat { float shade(float x) { return x * 87.0 + 86.0 + sin(x * 3.0); } }
struct M87 : IMat { float shade(float x) { return x * 88.0 + 87.0 + sin(x * 4.0); } }
struct M88 : IMat { float shade(float x) { return x * 89.0 + 88.0 + sin(x * 5.0); } }
struct M89 : IMat { float shade(float x) { return x * 90.0 + 89.0 + sin(x * 6.0); } }
struct M90 : IMat { float shade(float x) { return x * 91.0 + 90.0 + sin(x * 7.0); } }
struct M91 : IMat { float shade(float x) { return x * 92.0 + 91.0 + sin(x * 1.0); } }
struct M92 : IMat { float shade(float x) { return x * 93.0 + 92.0 + sin(x * 2.0); } }
struct M93 : IMat { float shade(float x) { return x * 94.0 + 93.0 + sin(x * 3.0); } }
struct M94 : IMat { float shade(float x) { return x * 95.0 + 94.0 + sin(x * 4.0); } }
struct M95 : IMat { float shade(float x) { return x * 96.0 + 95.0 + sin(x * 5.0); } }
struct M96 : IMat { float shade(float x) { return x * 97.0 + 96.0 + sin(x * 6.0); } }
struct M97 : IMat { float shade(float x) { return x * 98.0 + 97.0 + sin(x * 7.0); } }
struct M98 : IMat { float shade(float x) { return x * 99.0 + 98.0 + sin(x * 1.0); } }
struct M99 : IMat { float shade(float x) { return x * 100.0 + 99.0 + sin(x * 2.0); } }

struct Scene { IMat m; float w; }

float shadeScene(Scene sc, float x) { return sc.m.shade(x) * sc.w; }

[shader("compute")]
[numthreads(64,1,1)]
void computeMain(uint3 tid : SV_DispatchThreadID)
{
    float acc = 0.0;
    int base = int(tid.x);
    for (int i = 0; i < 100; ++i)
    {
        Scene sc;
        switch ((base + i) % 100)
        {
        case 0: sc.m = M0(); break;
        case 1: sc.m = M1(); break;
        case 2: sc.m = M2(); break;
        case 3: sc.m = M3(); break;
        case 4: sc.m = M4(); break;
        case 5: sc.m = M5(); break;
        case 6: sc.m = M6(); break;
        case 7: sc.m = M7(); break;
        case 8: sc.m = M8(); break;
        case 9: sc.m = M9(); break;
        case 10: sc.m = M10(); break;
        case 11: sc.m = M11(); break;
        case 12: sc.m = M12(); break;
        case 13: sc.m = M13(); break;
        case 14: sc.m = M14(); break;
        case 15: sc.m = M15(); break;
        case 16: sc.m = M16(); break;
        case 17: sc.m = M17(); break;
        case 18: sc.m = M18(); break;
        case 19: sc.m = M19(); break;
        case 20: sc.m = M20(); break;
        case 21: sc.m = M21(); break;
        case 22: sc.m = M22(); break;
        case 23: sc.m = M23(); break;
        case 24: sc.m = M24(); break;
        case 25: sc.m = M25(); break;
        case 26: sc.m = M26(); break;
        case 27: sc.m = M27(); break;
        case 28: sc.m = M28(); break;
        case 29: sc.m = M29(); break;
        case 30: sc.m = M30(); break;
        case 31: sc.m = M31(); break;
        case 32: sc.m = M32(); break;
        case 33: sc.m = M33(); break;
        case 34: sc.m = M34(); break;
        case 35: sc.m = M35(); break;
        case 36: sc.m = M36(); break;
        case 37: sc.m = M37(); break;
        case 38: sc.m = M38(); break;
        case 39: sc.m = M39(); break;
        case 40: sc.m = M40(); break;
        case 41: sc.m = M41(); break;
        case 42: sc.m = M42(); break;
        case 43: sc.m = M43(); break;
        case 44: sc.m = M44(); break;
        case 45: sc.m = M45(); break;
        case 46: sc.m = M46(); break;
        case 47: sc.m = M47(); break;
        case 48: sc.m = M48(); break;
        case 49: sc.m = M49(); break;
        case 50: sc.m = M50(); break;
        case 51: sc.m = M51(); break;
        case 52: sc.m = M52(); break;
        case 53: sc.m = M53(); break;
        case 54: sc.m = M54(); break;
        case 55: sc.m = M55(); break;
        case 56: sc.m = M56(); break;
        case 57: sc.m = M57(); break;
        case 58: sc.m = M58(); break;
        case 59: sc.m = M59(); break;
        case 60: sc.m = M60(); break;
        case 61: sc.m = M61(); break;
        case 62: sc.m = M62(); break;
        case 63: sc.m = M63(); break;
        case 64: sc.m = M64(); break;
        case 65: sc.m = M65(); break;
        case 66: sc.m = M66(); break;
        case 67: sc.m = M67(); break;
        case 68: sc.m = M68(); break;
        case 69: sc.m = M69(); break;
        case 70: sc.m = M70(); break;
        case 71: sc.m = M71(); break;
        case 72: sc.m = M72(); break;
        case 73: sc.m = M73(); break;
        case 74: sc.m = M74(); break;
        case 75: sc.m = M75(); break;
        case 76: sc.m = M76(); break;
        case 77: sc.m = M77(); break;
        case 78: sc.m = M78(); break;
        case 79: sc.m = M79(); break;
        case 80: sc.m = M80(); break;
        case 81: sc.m = M81(); break;
        case 82: sc.m = M82(); break;
        case 83: sc.m = M83(); break;
        case 84: sc.m = M84(); break;
        case 85: sc.m = M85(); break;
        case 86: sc.m = M86(); break;
        case 87: sc.m = M87(); break;
        case 88: sc.m = M88(); break;
        case 89: sc.m = M89(); break;
        case 90: sc.m = M90(); break;
        case 91: sc.m = M91(); break;
        case 92: sc.m = M92(); break;
        case 93: sc.m = M93(); break;
        case 94: sc.m = M94(); break;
        case 95: sc.m = M95(); break;
        case 96: sc.m = M96(); break;
        case 97: sc.m = M97(); break;
        case 98: sc.m = M98(); break;
        case 99: sc.m = M99(); break;
        default: sc.m = M0(); break;
        }
        sc.w = float(i);
        acc += shadeScene(sc, outBuf[0] + float(i));
    }
    outBuf[0] = acc;
}

Phase composition across releases

Across releases

Daily tip-of-tree (last 30 days)

Daily window progress

Reproduce

Compiled Slang source

existential_aggregate.slang (229 lines)