[SYCL-MLIR][DetectReduction] Disallow transformation when exists may alias operations in loop #9055
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whitneywhtsang
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polygeist/test/polygeist-opt/sycl/matrix_multiply_reduction.mlir
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Plan to merge this PR after implementing a fix. But please still review it. |
sommerlukas
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etiotto
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polygeist/tools/cgeist/Test/polybench/linear-algebra/kernels/2mm/2mm.c
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Verified that with this PR and `-D__SYCL_DISABLE_PARALLEL_FOR_RANGE_ROUNDING__`, SYCL-MLIR is able to perform scalar replacement on reduction loop on the SYCL-Bench workloads identified before, even with the fix in #9055. O3 | Previously measured gains | Only PR9187 | PR9187+PR9055 -- | -- | -- | -- 2mm | 12% | 12% | 12% 3mm | 13% | 12% | 11% covariance | 50% | 50% | 0% gemm | 12% | 12% | 11% gramschmidt | 14% + 18% (LICM versioning) | 33% | 33% syrk | 5% | 5% | 5% => No performance regressions with just this PR. => Lost `covariance` 50% gain after specializing the function, because 2 of the 3 accessors actually overlap! ``` auto data = data_buffer.get_access<access::mode::read>(cgh); auto symmat = symmat_buffer.get_access<access::mode::discard_write>(cgh); auto symmat2 = symmat_buffer.get_access<access::mode::discard_write>(cgh); ``` Not sure why it is written that way, with the simple source code change below (which remove `symmat2` and always use `symmat`), the 50% gain is recovered. ``` +++ b/polybench/covariance.cpp @@ -110,7 +110,6 @@ public: - auto symmat2 = symmat_buffer.get_access<access::mode::discard_write>(cgh); @@ -122,7 +121,7 @@ public: - symmat2[{j2, j1}] = symmat[{j1, j2}]; + symmat[{j2, j1}] = symmat[{j1, j2}]; ``` If we want to get the gain without source code change, then we need to version by only checking if `symmat` and `data` overlap, which we need the context, we may want to perform loop versioning in detect reduction pass. Notice the inner loop with the opportunity doesn't use `symmat2`: ``` for(size_t i = 1; i <= N_; i++) symmat[{j1, j2}] += data[{i, j1}] * data[{i, j2}]; ``` Note: A number of KernelFusion test cases are moved to xfail, as accessors cannot be internalize when they are used by a ptrtoint operation. (#9188) --------- Signed-off-by: Tsang, Whitney <whitney.tsang@intel.com>
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…e are may alias operations in loop Signed-off-by: Tsang, Whitney <whitney.tsang@intel.com>
Signed-off-by: Tsang, Whitney <whitney.tsang@intel.com>
Signed-off-by: Tsang, Whitney <whitney.tsang@intel.com>
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Original loop:
Optimized loop:
This is incorrect if A and B may alias because
B[i]may be different after updatingA[0].