1. Lockstep execution

2. anotherCheapFunction(); } else aMoreExpensiveFunction();
exec mask: … …. 1
Thread 0 (fastpath is true)
Thread 1 (fastPath is false)
if ( fastPath ) {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();
if ( fastPath ) {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();

3. anotherCheapFunction(); } else aMoreExpensiveFunction();
exec mask: … …. 1
Thread 0 (fastpath is true)
Thread 1 (fastPath is false)
if ( fastPath ) {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();
if ( fastPath ) {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();

4. anotherCheapFunction(); } else aMoreExpensiveFunction();
exec mask: … …. 1
Thread 0 (fastpath is true)
Thread 1 (fastPath is false)
if ( fastPath ) {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();
if ( fastPath ) {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();

5. anotherCheapFunction(); } else aMoreExpensiveFunction();
exec mask: … …. 1
Thread 0 (fastpath is true)
Thread 1 (fastPath is false)
if ( fastPath ) {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();
if ( fastPath ) {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();

6. anotherCheapFunction(); } else aMoreExpensiveFunction();
exec mask: … …. 1
Thread 0 (fastpath is true)
Thread 1 (fastPath is false)
if ( fastPath ) {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();
if ( fastPath ) {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();

7. anotherCheapFunction(); } else aMoreExpensiveFunction();
exec mask: … …. 1
Thread 0 (fastpath is true)
Thread 1 (fastPath is false)
if ( fastPath ) {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();
if ( fastPath ) {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();
…rest of the code…
…rest of the code…

8. Scalarized execution

9. bool s_fastPath = WaveAllTrue(fastPath);
exec mask: … …. 1
Thread 0 (fastpath is true)
Thread 1 (fastPath is false)
bool s_fastPath = WaveAllTrue(fastPath);
if ( s_fastPath ) // false across the whole wave {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();
bool s_fastPath = WaveAllTrue(fastPath);
if ( s_fastPath ) // false across the whole wave {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();

10. bool s_fastPath = WaveAllTrue(fastPath);
exec mask: … …. 1
Thread 0 (fastpath is true)
Thread 1 (fastPath is false)
bool s_fastPath = WaveAllTrue(fastPath);
if ( s_fastPath ) // false across the whole wave {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();
bool s_fastPath = WaveAllTrue(fastPath);
if ( s_fastPath ) // false across the whole wave {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();

11. bool s_fastPath = WaveAllTrue(fastPath);
exec mask: … …. 1
Thread 0 (fastpath is true)
Thread 1 (fastPath is false)
bool s_fastPath = WaveAllTrue(fastPath);
if ( s_fastPath ) // false across the whole wave {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();
bool s_fastPath = WaveAllTrue(fastPath);
if ( s_fastPath ) // false across the whole wave {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();

12. bool s_fastPath = WaveAllTrue(fastPath);
exec mask: … …. 1
Thread 0 (fastpath is true)
Thread 1 (fastPath is false)
bool s_fastPath = WaveAllTrue(fastPath);
if ( s_fastPath ) // false across the whole wave {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();
bool s_fastPath = WaveAllTrue(fastPath);
if ( s_fastPath ) // false across the whole wave {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();

13. bool s_fastPath = WaveAllTrue(fastPath);
exec mask: … …. 1
Thread 0 (fastpath is true)
Thread 1 (fastPath is false)
bool s_fastPath = WaveAllTrue(fastPath);
if ( s_fastPath ) // false across the whole wave {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();
bool s_fastPath = WaveAllTrue(fastPath);
if ( s_fastPath ) // false across the whole wave {
aCheapFunction();
anotherCheapFunction(); }
else
aMoreExpensiveFunction();
anotherExpensiveFunction();
…rest of the code…
…rest of the code…

14. Wave vis

15. Wave Wave thread thread thread thread thread thread thread thread

16. Some intrinsics

17. Intrinsic
Description
uint WaveGetLaneIndex()
Returns the index of the lane within the current lane (in a VGPR of course)
uint4 WaveActiveBallot(bool)
Returns a 64-bit mask containing the result of the passed predicate for all the active lanes. This mask will be in a SGPR.
bool WaveActiveAnyTrue(bool)
Probably using ballot, it returns whether the predicate passed is true for any active lane. Result is in SGPR.
bool WaveActiveAllTrue(bool)
Probably using ballot, it returns whether the predicate passed is true for all active lane. Result is in SGPR.
<type> WaveReadLaneFirst(<type>)
Returns the value of the passed expression for the first active lane in the wave. Result is in SGPR.
<type> WaveActiveMin(<type>)
Returns the minimum value of the passed expression across all active lanes in the wave. Result is in SGPR.

18. Latency hiding example

19. float4 b = b0 + b1;
float4 c = a + b;
float4 d = c * e;
float4 f = load_data();
float4 g = f + h;
… rest of code …
float4 b = b0 + b1;
float4 c = a + b;
float4 d = c * e;
float4 f = load_data();
float4 g = f + h;
… rest of code …

20. float4 b = b0 + b1;
float4 c = a + b;
float4 d = c * e;
float4 f = load_data();
float4 g = f + h;
… rest of code …
float4 b = b0 + b1;
float4 c = a + b;
float4 d = c * e;
float4 f = load_data();
float4 g = f + h;
… rest of code …

21. float4 b = b0 + b1;
float4 c = a + b;
float4 d = c * e;
float4 f = load_data();
float4 g = f + h;
… rest of code …
float4 b = b0 + b1;
float4 c = a + b;
float4 d = c * e;
float4 f = load_data();
float4 g = f + h;
… rest of code …

22. float4 b = b0 + b1;
float4 c = a + b;
float4 d = c * e;
float4 f = load_data();
float4 g = f + h;
… rest of code …
float4 b = b0 + b1;
float4 c = a + b;
float4 d = c * e;
float4 f = load_data();
float4 g = f + h;
… rest of code …

23. float4 b = b0 + b1;
float4 c = a + b;
float4 d = c * e;
float4 f = load_data();
float4 g = f + h;
… rest of code …
float4 b = b0 + b1;
float4 c = a + b;
float4 d = c * e;
float4 f = load_data();
float4 g = f + h;
… rest of code …

24. float4 b = b0 + b1;
float4 c = a + b;
float4 d = c * e;
float4 f = load_data();
float4 g = f + h;
… rest of code …
float4 b = b0 + b1;
float4 c = a + b;
float4 d = c * e;
float4 f = load_data();
float4 g = f + h;
… rest of code …

25. float4 b = b0 + b1;
float4 c = a + b;
float4 d = c * e;
float4 f = load_data();
float4 g = f + h;
… rest of code …
float4 b = b0 + b1;
float4 c = a + b;
float4 d = c * e;
float4 f = load_data();
float4 g = f + h;
… rest of code …

26. float4 b = b0 + b1;
float4 c = a + b;
float4 d = c * e;
float4 f = load_data();
….wait for result…
float4 g = f + h;
… rest of code …
float4 b = b0 + b1;
float4 c = a + b;
float4 d = c * e;
float4 f = load_data();
float4 g = f + h;
… rest of code …

27. float4 b = b0 + b1;
float4 c = a + b;
float4 d = c * e;
float4 f = load_data();
….wait for result…
float4 g = f + h;
… rest of code …
float4 b = b0 + b1;
float4 c = a + b;
float4 d = c * e;
float4 f = load_data();
float4 g = f + h;
… rest of code …

28. float4 b = b0 + b1; float4 c = a + b; float4 d = c * e;
float4 f = load_data();
….wait for result…
float4 g = f + h;
… rest of code …
float4 b = b0 + b1;
float4 c = a + b;
float4 d = c * e;
float4 f = load_data();
float4 g = f + h;
… rest of code …
ready

29. Single wave overlap multiple tiles

30. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

31. Non-scalarized light loop

32. 2 3 4 1 2 3 6 3 5 v_lightIdx = 0 v_lightIdx = 1 v_lightIdx = 02 3 4 1 2 3 6 3 5
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
v_lightIdx = 0
v_lightIdx = 1
v_lightIdx = 0

33. 2 3 4 1 2 3 6 3 5 v_lightIdx = 0 v_lightIdx = 1 v_lightIdx = 02 3 4 1 2 3 6 3 5
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
v_lightIdx = 0
v_lightIdx = 1
v_lightIdx = 0

34. 2 3 4 1 2 3 6 3 5 v_lightIdx = 0 v_lightIdx = 1 v_lightIdx = 02 3 4 1 2 3 6 3 5
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
v_lightIdx = 0
v_lightIdx = 1
v_lightIdx = 0

35. 2 3 4 1 2 3 6 3 5 v_lightIdx = 2 v_lightIdx = 2 v_lightIdx = 32 3 4 1 2 3 6 3 5
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
v_lightIdx = 2
v_lightIdx = 2
v_lightIdx = 3

36. 2 3 4 1 2 3 6 3 5 v_lightIdx = 2 v_lightIdx = 2 v_lightIdx = 32 3 4 1 2 3 6 3 5
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
v_lightIdx = 2
v_lightIdx = 2
v_lightIdx = 3

37. 2 3 4 1 2 3 6 3 5 v_lightIdx = 2 v_lightIdx = 2 v_lightIdx = 32 3 4 1 2 3 6 3 5
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
v_lightIdx = 2
v_lightIdx = 2
v_lightIdx = 3

38. 2 3 4 1 2 3 6 3 5 v_lightIdx = 3 v_lightIdx = 3 v_lightIdx = 52 3 4 1 2 3 6 3 5
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
v_lightIdx = 3
v_lightIdx = 3
v_lightIdx = 5

39. 2 3 4 1 2 3 6 3 5 v_lightIdx = 3 v_lightIdx = 3 v_lightIdx = 52 3 4 1 2 3 6 3 5
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
v_lightIdx = 3
v_lightIdx = 3
v_lightIdx = 5

40. 2 3 4 1 2 3 6 3 5 v_lightIdx = 3 v_lightIdx = 3 v_lightIdx = 52 3 4 1 2 3 6 3 5
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
v_lightIdx = 3
v_lightIdx = 3
v_lightIdx = 5

41. 2 3 4 1 2 3 6 3 5 v_lightIdx = 4 v_lightIdx = 6 v_lightIdx = 52 3 4 1 2 3 6 3 5
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
v_lightIdx = 4
v_lightIdx = 6
v_lightIdx = 5

42. 2 3 4 1 2 3 6 3 5 v_lightIdx = 4 v_lightIdx = 6 v_lightIdx = 52 3 4 1 2 3 6 3 5
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
v_lightIdx = 4
v_lightIdx = 6
v_lightIdx = 5

43. 2 3 4 1 2 3 6 3 5 v_lightIdx = 4 v_lightIdx = 6 v_lightIdx = 52 3 4 1 2 3 6 3 5
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
StructuredBuffer<LightData> Lights;
ByteAddressBuffer Indices; …
uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
for( i = 0; i < v_lightCount; ++i) {
uint v_lightIdx = GetLightIdx(v_lightStart, i);
LightData v_light = Lights[v_lightIdx];
ProcessLight(v_light); }
v_lightIdx = 4
v_lightIdx = 6
v_lightIdx = 5

44. Scalarization approach #1 – Step by Step

45. lane ID v_cellIdx A C B 1 v_cellIdx lane mask exec mask s_cellIdx
uint v_cellIdx = GetCellIdx();
uint v_laneID = WaveGetLaneIndex();
ulong execMask = 0xffffffff;
ulong curLaneMask = ulong(1) << ulong(v_laneID);
while ( ( execMask & curLaneMask ) != 0 ) {
uint s_cellIdx = WaveReadFirstLane(v_cellIdx);
ulong laneMask = WaveBallot( v_cellIdx == s_cellIdx );
execMask = execMask & ~laneMask;
if (v_cellIdx == s_cellIdx )
ProcessLightsInCell(s_cellIdx); }
void ProcessLightsInCell(uint s_cellIdx)
{s_lightStart, s_lightCount} = GetCellIndices(s_cellIdx);
for( i = 0; i < s_lightCount; ++i)
uint s_lightIdx = GetLightIdx(s_lightStart, i);
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light);
v_cellIdx A C B
lane mask
exec mask 1
s_cellIdx

46. lane ID v_cellIdx A C B 1 A v_cellIdx lane mask exec mask s_cellIdx
uint v_cellIdx = GetCellIdx();
uint v_laneID = WaveGetLaneIndex();
ulong execMask = 0xffffffff;
ulong curLaneMask = ulong(1) << ulong(v_laneID);
while ( ( execMask & curLaneMask ) != 0 ) {
uint s_cellIdx = WaveReadFirstLane(v_cellIdx);
ulong laneMask = WaveBallot( v_cellIdx == s_cellIdx );
execMask = execMask & ~laneMask;
if (v_cellIdx == s_cellIdx )
ProcessLightsInCell(s_cellIdx); }
void ProcessLightsInCell(uint s_cellIdx)
{s_lightStart, s_lightCount} = GetCellIndices(s_cellIdx);
for( i = 0; i < s_lightCount; ++i)
uint s_lightIdx = GetLightIdx(s_lightStart, i);
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light);
v_cellIdx A C B
lane mask
exec mask 1
s_cellIdx A

47. lane ID v_cellIdx A C B 1 1 A v_cellIdx lane mask exec mask s_cellIdx
uint v_cellIdx = GetCellIdx();
uint v_laneID = WaveGetLaneIndex();
ulong execMask = 0xffffffff;
ulong curLaneMask = ulong(1) << ulong(v_laneID);
while ( ( execMask & curLaneMask ) != 0 ) {
uint s_cellIdx = WaveReadFirstLane(v_cellIdx);
ulong laneMask = WaveBallot( v_cellIdx == s_cellIdx );
execMask = execMask & ~laneMask;
if (v_cellIdx == s_cellIdx )
ProcessLightsInCell(s_cellIdx); }
void ProcessLightsInCell(uint s_cellIdx)
{s_lightStart, s_lightCount} = GetCellIndices(s_cellIdx);
for( i = 0; i < s_lightCount; ++i)
uint s_lightIdx = GetLightIdx(s_lightStart, i);
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light);
v_cellIdx A C B
lane mask 1
exec mask 1
s_cellIdx A

48. lane ID v_cellIdx A C B 1 1 A v_cellIdx lane mask exec mask s_cellIdx
uint v_cellIdx = GetCellIdx();
uint v_laneID = WaveGetLaneIndex();
ulong execMask = 0xffffffff;
ulong curLaneMask = ulong(1) << ulong(v_laneID);
while ( ( execMask & curLaneMask ) != 0 ) {
uint s_cellIdx = WaveReadFirstLane(v_cellIdx);
ulong laneMask = WaveBallot( v_cellIdx == s_cellIdx );
execMask = execMask & ~laneMask;
if (v_cellIdx == s_cellIdx )
ProcessLightsInCell(s_cellIdx); }
void ProcessLightsInCell(uint s_cellIdx)
{s_lightStart, s_lightCount} = GetCellIndices(s_cellIdx);
for( i = 0; i < s_lightCount; ++i)
uint s_lightIdx = GetLightIdx(s_lightStart, i);
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light);
v_cellIdx A C B
lane mask 1
exec mask 1
s_cellIdx A

49. lane ID v_cellIdx A C B 1 1 A v_cellIdx lane mask exec mask s_cellIdx
uint v_cellIdx = GetCellIdx();
uint v_laneID = WaveGetLaneIndex();
ulong execMask = 0xffffffff;
ulong curLaneMask = ulong(1) << ulong(v_laneID);
while ( ( execMask & curLaneMask ) != 0 ) {
uint s_cellIdx = WaveReadFirstLane(v_cellIdx);
ulong laneMask = WaveBallot( v_cellIdx == s_cellIdx );
execMask = execMask & ~laneMask;
if (v_cellIdx == s_cellIdx )
ProcessLightsInCell(s_cellIdx); }
void ProcessLightsInCell(uint s_cellIdx)
{s_lightStart, s_lightCount} = GetCellIndices(s_cellIdx);
for( i = 0; i < s_lightCount; ++i)
uint s_lightIdx = GetLightIdx(s_lightStart, i);
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light);
v_cellIdx A C B
lane mask 1
exec mask 1
s_cellIdx A

50. lane ID v_cellIdx A C B 1 1 A v_cellIdx lane mask exec mask s_cellIdx
uint v_cellIdx = GetCellIdx();
uint v_laneID = WaveGetLaneIndex();
ulong execMask = 0xffffffff;
ulong curLaneMask = ulong(1) << ulong(v_laneID);
while ( ( execMask & curLaneMask ) != 0 ) {
uint s_cellIdx = WaveReadFirstLane(v_cellIdx);
ulong laneMask = WaveBallot( v_cellIdx == s_cellIdx );
execMask = execMask & ~laneMask;
if (v_cellIdx == s_cellIdx )
ProcessLightsInCell(s_cellIdx); }
void ProcessLightsInCell(uint s_cellIdx)
{s_lightStart, s_lightCount} = GetCellIndices(s_cellIdx);
for( i = 0; i < s_lightCount; ++i)
uint s_lightIdx = GetLightIdx(s_lightStart, i);
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light);
v_cellIdx A C B
lane mask 1
exec mask 1
s_cellIdx A

51. lane ID v_cellIdx A C B 1 C v_cellIdx lane mask exec mask s_cellIdx
uint v_cellIdx = GetCellIdx();
uint v_laneID = WaveGetLaneIndex();
ulong execMask = 0xffffffff;
ulong curLaneMask = ulong(1) << ulong(v_laneID);
while ( ( execMask & curLaneMask ) != 0 ) {
uint s_cellIdx = WaveReadFirstLane(v_cellIdx);
ulong laneMask = WaveBallot( v_cellIdx == s_cellIdx );
execMask = execMask & ~laneMask;
if (v_cellIdx == s_cellIdx )
ProcessLightsInCell(s_cellIdx); }
void ProcessLightsInCell(uint s_cellIdx)
{s_lightStart, s_lightCount} = GetCellIndices(s_cellIdx);
for( i = 0; i < s_lightCount; ++i)
uint s_lightIdx = GetLightIdx(s_lightStart, i);
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light);
v_cellIdx A C B
lane mask
exec mask 1
s_cellIdx C

52. lane ID v_cellIdx A C B 1 1 C v_cellIdx lane mask exec mask s_cellIdx
uint v_cellIdx = GetCellIdx();
uint v_laneID = WaveGetLaneIndex();
ulong execMask = 0xffffffff;
ulong curLaneMask = ulong(1) << ulong(v_laneID);
while ( ( execMask & curLaneMask ) != 0 ) {
uint s_cellIdx = WaveReadFirstLane(v_cellIdx);
ulong laneMask = WaveBallot( v_cellIdx == s_cellIdx );
execMask = execMask & ~laneMask;
if (v_cellIdx == s_cellIdx )
ProcessLightsInCell(s_cellIdx); }
void ProcessLightsInCell(uint s_cellIdx)
{s_lightStart, s_lightCount} = GetCellIndices(s_cellIdx);
for( i = 0; i < s_lightCount; ++i)
uint s_lightIdx = GetLightIdx(s_lightStart, i);
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light);
v_cellIdx A C B
lane mask 1
exec mask 1
s_cellIdx C

53. lane ID v_cellIdx A C B 1 1 C v_cellIdx lane mask exec mask s_cellIdx
uint v_cellIdx = GetCellIdx();
uint v_laneID = WaveGetLaneIndex();
ulong execMask = 0xffffffff;
ulong curLaneMask = ulong(1) << ulong(v_laneID);
while ( ( execMask & curLaneMask ) != 0 ) {
uint s_cellIdx = WaveReadFirstLane(v_cellIdx);
ulong laneMask = WaveBallot( v_cellIdx == s_cellIdx );
execMask = execMask & ~laneMask;
if (v_cellIdx == s_cellIdx )
ProcessLightsInCell(s_cellIdx); }
void ProcessLightsInCell(uint s_cellIdx)
{s_lightStart, s_lightCount} = GetCellIndices(s_cellIdx);
for( i = 0; i < s_lightCount; ++i)
uint s_lightIdx = GetLightIdx(s_lightStart, i);
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light);
v_cellIdx A C B
lane mask 1
exec mask 1
s_cellIdx C

54. lane ID v_cellIdx A C B 1 1 C v_cellIdx lane mask exec mask s_cellIdx
uint v_cellIdx = GetCellIdx();
uint v_laneID = WaveGetLaneIndex();
ulong execMask = 0xffffffff;
ulong curLaneMask = ulong(1) << ulong(v_laneID);
while ( ( execMask & curLaneMask ) != 0 ) {
uint s_cellIdx = WaveReadFirstLane(v_cellIdx);
ulong laneMask = WaveBallot( v_cellIdx == s_cellIdx );
execMask = execMask & ~laneMask;
if (v_cellIdx == s_cellIdx )
ProcessLightsInCell(s_cellIdx); }
void ProcessLightsInCell(uint s_cellIdx)
{s_lightStart, s_lightCount} = GetCellIndices(s_cellIdx);
for( i = 0; i < s_lightCount; ++i)
uint s_lightIdx = GetLightIdx(s_lightStart, i);
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light);
v_cellIdx A C B
lane mask 1
exec mask 1
s_cellIdx C

55. lane ID v_cellIdx A C B 1 1 C v_cellIdx lane mask exec mask s_cellIdx
uint v_cellIdx = GetCellIdx();
uint v_laneID = WaveGetLaneIndex();
ulong execMask = 0xffffffff;
ulong curLaneMask = ulong(1) << ulong(v_laneID);
while ( ( execMask & curLaneMask ) != 0 ) {
uint s_cellIdx = WaveReadFirstLane(v_cellIdx);
ulong laneMask = WaveBallot( v_cellIdx == s_cellIdx );
execMask = execMask & ~laneMask;
if (v_cellIdx == s_cellIdx )
ProcessLightsInCell(s_cellIdx); }
void ProcessLightsInCell(uint s_cellIdx)
{s_lightStart, s_lightCount} = GetCellIndices(s_cellIdx);
for( i = 0; i < s_lightCount; ++i)
uint s_lightIdx = GetLightIdx(s_lightStart, i);
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light);
v_cellIdx A C B
lane mask 1
exec mask 1
s_cellIdx C

56. A C B 1 B v_cellIdx lane mask exec mask s_cellIdx
uint v_cellIdx = GetCellIdx();
uint v_laneID = WaveGetLaneIndex();
ulong execMask = 0xffffffff;
ulong curLaneMask = ulong(1) << ulong(v_laneID);
while ( ( execMask & curLaneMask ) != 0 ) {
uint s_cellIdx = WaveReadFirstLane(v_cellIdx);
ulong laneMask = WaveBallot( v_cellIdx == s_cellIdx );
execMask = execMask & ~laneMask;
if (v_cellIdx == s_cellIdx )
ProcessLightsInCell(s_cellIdx); }
void ProcessLightsInCell(uint s_cellIdx)
{s_lightStart, s_lightCount} = GetCellIndices(s_cellIdx);
for( i = 0; i < s_lightCount; ++i)
uint s_lightIdx = GetLightIdx(s_lightStart, i);
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light);
v_cellIdx A C B
lane mask
exec mask 1
s_cellIdx B

57. A C B 1 1 B v_cellIdx lane mask exec mask s_cellIdx
uint v_cellIdx = GetCellIdx();
uint v_laneID = WaveGetLaneIndex();
ulong execMask = 0xffffffff;
ulong curLaneMask = ulong(1) << ulong(v_laneID);
while ( ( execMask & curLaneMask ) != 0 ) {
uint s_cellIdx = WaveReadFirstLane(v_cellIdx);
ulong laneMask = WaveBallot( v_cellIdx == s_cellIdx );
execMask = execMask & ~laneMask;
if (v_cellIdx == s_cellIdx )
ProcessLightsInCell(s_cellIdx); }
void ProcessLightsInCell(uint s_cellIdx)
{s_lightStart, s_lightCount} = GetCellIndices(s_cellIdx);
for( i = 0; i < s_lightCount; ++i)
uint s_lightIdx = GetLightIdx(s_lightStart, i);
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light);
v_cellIdx A C B
lane mask 1
exec mask 1
s_cellIdx B

58. A C B 1 B v_cellIdx lane mask exec mask s_cellIdx
uint v_cellIdx = GetCellIdx();
uint v_laneID = WaveGetLaneIndex();
ulong execMask = 0xffffffff;
ulong curLaneMask = ulong(1) << ulong(v_laneID);
while ( ( execMask & curLaneMask ) != 0 ) {
uint s_cellIdx = WaveReadFirstLane(v_cellIdx);
ulong laneMask = WaveBallot( v_cellIdx == s_cellIdx );
execMask = execMask & ~laneMask;
if (v_cellIdx == s_cellIdx )
ProcessLightsInCell(s_cellIdx); }
void ProcessLightsInCell(uint s_cellIdx)
{s_lightStart, s_lightCount} = GetCellIndices(s_cellIdx);
for( i = 0; i < s_lightCount; ++i)
uint s_lightIdx = GetLightIdx(s_lightStart, i);
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light);
v_cellIdx A C B
lane mask 1
exec mask
s_cellIdx B

59. A C B 1 B v_cellIdx lane mask exec mask s_cellIdx
uint v_cellIdx = GetCellIdx();
uint v_laneID = WaveGetLaneIndex();
ulong execMask = 0xffffffff;
ulong curLaneMask = ulong(1) << ulong(v_laneID);
while ( ( execMask & curLaneMask ) != 0 ) {
uint s_cellIdx = WaveReadFirstLane(v_cellIdx);
ulong laneMask = WaveBallot( v_cellIdx == s_cellIdx );
execMask = execMask & ~laneMask;
if (v_cellIdx == s_cellIdx )
ProcessLightsInCell(s_cellIdx); }
void ProcessLightsInCell(uint s_cellIdx)
{s_lightStart, s_lightCount} = GetCellIndices(s_cellIdx);
for( i = 0; i < s_lightCount; ++i)
uint s_lightIdx = GetLightIdx(s_lightStart, i);
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light);
v_cellIdx A C B
lane mask 1
exec mask
s_cellIdx B

60. A C B 1 B v_cellIdx lane mask exec mask s_cellIdx
uint v_cellIdx = GetCellIdx();
uint v_laneID = WaveGetLaneIndex();
ulong execMask = 0xffffffff;
ulong curLaneMask = ulong(1) << ulong(v_laneID);
while ( ( execMask & curLaneMask ) != 0 ) {
uint s_cellIdx = WaveReadFirstLane(v_cellIdx);
ulong laneMask = WaveBallot( v_cellIdx == s_cellIdx );
execMask = execMask & ~laneMask;
if (v_cellIdx == s_cellIdx )
ProcessLightsInCell(s_cellIdx); }
void ProcessLightsInCell(uint s_cellIdx)
{s_lightStart, s_lightCount} = GetCellIndices(s_cellIdx);
for( i = 0; i < s_lightCount; ++i)
uint s_lightIdx = GetLightIdx(s_lightStart, i);
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light);
v_cellIdx A C B
lane mask 1
exec mask
s_cellIdx B

61. A C B B v_cellIdx lane mask exec mask s_cellIdx
uint v_cellIdx = GetCellIdx();
uint v_laneID = WaveGetLaneIndex();
ulong execMask = 0xffffffff;
ulong curLaneMask = ulong(1) << ulong(v_laneID);
while ( ( execMask & curLaneMask ) != 0 ) {
uint s_cellIdx = WaveReadFirstLane(v_cellIdx);
ulong laneMask = WaveBallot( v_cellIdx == s_cellIdx );
execMask = execMask & ~laneMask;
if (v_cellIdx == s_cellIdx )
ProcessLightsInCell(s_cellIdx); }
… rest of code …
void ProcessLightsInCell(uint s_cellIdx)
{s_lightStart, s_lightCount} = GetCellIndices(s_cellIdx);
for( i = 0; i < s_lightCount; ++i)
uint s_lightIdx = GetLightIdx(s_lightStart, i);
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light);
v_cellIdx A C B
lane mask
exec mask
s_cellIdx B

62. uint v_cellIdx = GetCellIdx();
uint v_laneID = WaveGetLaneIndex();
ulong execMask = 0xffffffff;
ulong curLaneMask = ulong(1) << ulong(v_laneID);
while ( ( execMask & curLaneMask ) != 0 ) {
uint s_cellIdx = WaveReadFirstLane(v_cellIdx);
ulong laneMask = WaveBallot( v_cellIdx == s_cellIdx );
execMask = execMask & ~laneMask;
if (v_cellIdx == s_cellIdx )
ProcessLightsInCell(s_cellIdx); }
… rest of code …
void ProcessLightsInCell(uint s_cellIdx)
{s_lightStart, s_lightCount} = GetCellIndices(s_cellIdx);
for( i = 0; i < s_lightCount; ++i)
uint s_lightIdx = GetLightIdx(s_lightStart, i);
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light);

63. Multiple evaluations with approach #1

64. Cell Index
Cell Content A 42 44 45 46 B 41 C 40
Light index
Number of code evals 40 41 42 44 45 46

65. Cell Index
Cell Content A 42 44 45 46 B 41 C 40
Light index
Number of code evals 40 41 42 1 44 45 46
Evaluating cell A

66. Cell Index
Cell Content A 42 44 45 46 B 41 C 40
Light index
Number of code evals 40 41 1 42 2 44 45 46
Evaluating cell B

67. Cell Index
Cell Content A 42 44 45 46 B 41 C 40
Light index
Number of code evals 40 1 41 2 42 3 44 45 46
Evaluating cell C

68. Scalarization approach #2 – Step by Step

69. uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx
v_lightIdx
v_cellIdx A C B
lightOffset
Cells content: A 42 44 45 46 B 41 C 40

70. A C B A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx
v_lightIdx
v_cellIdx A C B
lightOffset A 42 44 45 46 B 41 C 40

71. A C B A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx
v_lightIdx 42 40 41
v_cellIdx A C B
lightOffset A 42 44 45 46 B 41 C 40

72. 40 A C B A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 40
v_lightIdx 42 40 41
v_cellIdx A C B
lightOffset A 42 44 45 46 B 41 C 40

73. 40 A C B A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 40
v_lightIdx 42 40 41
v_cellIdx A C B
lightOffset A 42 44 45 46 B 41 C 40

74. 40 A C B 1 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 40
v_lightIdx 42 40 41
v_cellIdx A C B
lightOffset 1 A 42 44 45 46 B 41 C 40

75. 40 A C B 1 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 40
v_lightIdx 42 40 41
v_cellIdx A C B
lightOffset 1 A 42 44 45 46 B 41 C 40

76. A C B 1 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx
v_lightIdx 42 41
v_cellIdx A C B
lightOffset 1 A 42 44 45 46 B 41 C 40

77. 41 A C B 1 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 41
v_lightIdx 42 41
v_cellIdx A C B
lightOffset 1 A 42 44 45 46 B 41 C 40

78. 41 A C B 2 1 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 41
v_lightIdx 42 41
v_cellIdx A C B
lightOffset 2 1 A 42 44 45 46 B 41 C 40

79. 41 A C B 2 1 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 41
v_lightIdx 42 41
v_cellIdx A C B
lightOffset 2 1 A 42 44 45 46 B 41 C 40

80. A C B 2 1 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx
v_lightIdx 42
v_cellIdx A C B
lightOffset 2 1 A 42 44 45 46 B 41 C 40

81. 42 A C B 2 1 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 42
v_lightIdx 42
v_cellIdx A C B
lightOffset 2 1 A 42 44 45 46 B 41 C 40

82. 42 A C B 2 1 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 42
v_lightIdx 42
v_cellIdx A C B
lightOffset 2 1 A 42 44 45 46 B 41 C 40

83. 42 A C B 1 3 2 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 42
v_lightIdx 42
v_cellIdx A C B
lightOffset 1 3 2 A 42 44 45 46 B 41 C 40

84. 42 A C B 1 3 2 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 42
v_lightIdx 42
v_cellIdx A C B
lightOffset 1 3 2 A 42 44 45 46 B 41 C 40

85. A C B 1 3 2 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx
v_lightIdx 44 42 46
v_cellIdx A C B
lightOffset 1 3 2 A 42 44 45 46 B 41 C 40

86. 44 A C B 1 3 2 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 44
v_lightIdx 44 42 46
v_cellIdx A C B
lightOffset 1 3 2 A 42 44 45 46 B 41 C 40

87. 44 A C B 1 3 2 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 44
v_lightIdx 44 42 46
v_cellIdx A C B
lightOffset 1 3 2 A 42 44 45 46 B 41 C 40

88. 44 A C B 2 3 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 44
v_lightIdx 44 42 46
v_cellIdx A C B
lightOffset 2 3 A 42 44 45 46 B 41 C 40

89. 44 A C B 2 3 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 44
v_lightIdx 44 42 46
v_cellIdx A C B
lightOffset 2 3 A 42 44 45 46 B 41 C 40

90. A C B 2 3 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx
v_lightIdx 45 42 46
v_cellIdx A C B
lightOffset 2 3 A 42 44 45 46 B 41 C 40

91. 45 A C B 2 3 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 45
v_lightIdx 45 42 46
v_cellIdx A C B
lightOffset 2 3 A 42 44 45 46 B 41 C 40

92. 45 A C B 2 3 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 45
v_lightIdx 45 42 46
v_cellIdx A C B
lightOffset 2 3 A 42 44 45 46 B 41 C 40

93. 45 A C B 3 2 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 45
v_lightIdx 45 42 46
v_cellIdx A C B
lightOffset 3 2 A 42 44 45 46 B 41 C 40

94. 45 A C B 3 2 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 45
v_lightIdx 45 42 46
v_cellIdx A C B
lightOffset 3 2 A 42 44 45 46 B 41 C 40

95. A C B 3 2 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx
v_lightIdx 46 42
v_cellIdx A C B
lightOffset 3 2 A 42 44 45 46 B 41 C 40

96. 46 A C B 3 2 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 46
v_lightIdx 46 42
v_cellIdx A C B
lightOffset 3 2 A 42 44 45 46 B 41 C 40

97. 46 A C B 3 2 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 46
v_lightIdx 46 42
v_cellIdx A C B
lightOffset 3 2 A 42 44 45 46 B 41 C 40

98. 46 A C B 4 3 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 46
v_lightIdx 46 42
v_cellIdx A C B
lightOffset 4 3 A 42 44 45 46 B 41 C 40

99. 46 A C B 4 3 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx 46
v_lightIdx 46 42
v_cellIdx A C B
lightOffset 4 3 A 42 44 45 46 B 41 C 40

100. A C B 4 3 A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
s_lightIdx
v_lightIdx 46 42
v_cellIdx A C B
lightOffset 4 3 A 42 44 45 46 B 41 C 40

101. A 42 44 45 46 B 41 C 40 uint v_cellIdx = GetCellIdx();
{v_lightStart, v_lightCount} = GetCellIndices(v_cellIdx);
uint lightOffset = 0;
while(lightOffset < lightCount ) {
uint v_lightIdx = GetLightIdx(v_lightStart, lightOffset);
uint s_lightIdx = WaveActiveMin(v_lightIdx);
if(s_lightIdx == v_lightIdx)
v_lightOffset++;
LightData s_light = Lights[s_lightIdx];
ProcessLight(s_light); }
… rest of the code … A 42 44 45 46 B 41 C 40