atomic_or

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The atomic_or function atomically performs a bitwise OR between the current value and the input, storing the result. Returns the original value.

Signature

bwsl

atomic_or(dest, value)

Parameters

Parameter	Description
`dest`	Integer lvalue to modify atomically
`value`	Integer value to OR with

Return Value

Returns the original value at dest before the operation.

Example

bwsl

pipeline VisibilityMask {
  pass "ComputePass" {
    compute "Main" [1, 1, 1] {
    // Each thread sets its bit if object is visible
    if (isVisible(objectId)) {
        int bitMask = 1 << (objectId % 32);
        int wordIndex = objectId / 32;
        atomic_or(visibilityBuffer[wordIndex], bitMask);
    }
    }
  }
}

Common Use Cases

Set Flags

bwsl

// Set specific flag bit
int flagBit = 1 << flagIndex;
atomic_or(stateFlags, flagBit);

Visibility Bitmask

bwsl

// Mark object as visible
int objectBit = 1 << (objectId & 31);
atomic_or(visibilityMask[objectId >> 5], objectBit);

Feature Accumulation

bwsl

// Accumulate all features found
int featureMask = detectFeatures(position);
atomic_or(tileFeatures[tileId], featureMask);

Dirty Flags

bwsl

// Mark tile as needing update
int tileBit = 1 << tileIndex;
atomic_or(dirtyTiles, tileBit);

Collision Layers

bwsl

// Mark which collision layers are active
int layerMask = getCollisionLayer(objectId);
atomic_or(activeCollisionLayers, layerMask);

Set vs Clear

Use atomic_or to set bits. Use atomic_and with inverted mask to clear bits.

Initialization

When accumulating with OR, initialize to 0 so only bits explicitly set appear in the result.

Compiled Output

When compiled to GLSL:

glsl

atomicOr(dest, value)

When compiled to HLSL:

hlsl

InterlockedOr(dest, value, originalValue)

When compiled to SPIR-V:

Uses OpAtomicOr instruction.

Test atomic_or in a live shader

Signature

Parameters

Return Value

Example

Common Use Cases

Set Flags

Visibility Bitmask

Feature Accumulation

Dirty Flags

Collision Layers

Compiled Output

See Also