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Adds platform-specific warp mask to frag_layout_swizzle.cuh #7

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Merged
diptorupd merged 1 commit into from
Oct 2, 2025
Merged

Adds platform-specific warp mask to frag_layout_swizzle.cuh #7

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17 changes: 12 additions & 5 deletions libflashinfer/include/flashinfer/attention/generic/frag_layout_swizzle.cuh
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Original file line number Diff line number Diff line change
Expand Up @@ -10,20 +10,27 @@

#include "gpu_iface/platform.hpp"

// Define platform-specific full mask for warp/wavefront operations
#if defined(PLATFORM_CUDA_DEVICE)
constexpr uint32_t WARP_FULL_MASK = 0xffffffff; // 32-bit mask for CUDA
#elif defined(PLATFORM_HIP_DEVICE)
constexpr uint64_t WARP_FULL_MASK = 0xffffffffffffffffULL; // 64-bit mask for HIP
#endif

__device__ __forceinline__ uint32_t frag_layout_swizzle_16b_to_8b(uint32_t x) {
uint32_t tmp = __shfl_xor_sync(0xffffffff, x, 0x1);
uint32_t tmp = __shfl_xor_sync(WARP_FULL_MASK, x, 0x1);
x = __byte_perm(x, tmp, ((threadIdx.x & 0x1) == 0) ? 0x5410 : 0x3276);
tmp = __shfl_xor_sync(0xffffffff, x, 0x2);
tmp = __shfl_xor_sync(WARP_FULL_MASK, x, 0x2);
x = __byte_perm(x, tmp, ((threadIdx.x & 0x2) == 0) ? 0x5410 : 0x3276);
return x;
}

__device__ __forceinline__ uint32_t frag_layout_swizzle_16b_to_8b_trans(uint32_t x) {
uint32_t tmp = __shfl_xor_sync(0xffffffff, x, 0x4);
uint32_t tmp = __shfl_xor_sync(WARP_FULL_MASK, x, 0x4);
x = __byte_perm(x, tmp, ((threadIdx.x & 0x4) == 0) ? 0x6420 : 0x3175);
tmp = __shfl_xor_sync(0xffffffff, x, 0x8);
tmp = __shfl_xor_sync(WARP_FULL_MASK, x, 0x8);
x = __byte_perm(x, tmp, ((threadIdx.x & 0x8) == 0) ? 0x5410 : 0x3276);
tmp = __shfl_xor_sync(0xffffffff, x, 0x10);
tmp = __shfl_xor_sync(WARP_FULL_MASK, x, 0x10);
x = __byte_perm(x, tmp, ((threadIdx.x & 0x10) == 0) ? 0x5410 : 0x3276);
return x;
}
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