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32c30ddee7
We know that "CVTTPS2SI" returns 0x80000000 for out of range inputs (and for FP_TO_UINT, negative float values are undefined). We can use this to make unsigned conversions from vXf32 to vXi32 more efficient, particularly on targets without blend using the following logic: small := CVTTPS2SI(x); fp_to_ui(x) := small | (CVTTPS2SI(x - 2^31) & ARITHMETIC_RIGHT_SHIFT(small, 31)) Even on targets where "PBLENDVPS"/"PBLENDVB" exists, it is often a latency 2, low throughput instruction so this logic is applied there too (in particular for AVX2 also). It furthermore gets rid of one high latency floating point comparison in the previous lowering. @TomHender checked the correctness of this for all possible floats between -1 and 2^32 (both ends excluded). Original Patch by @TomHender (Tom Hender) Differential Revision: https://reviews.llvm.org/D89697 |
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