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Sanjay Patel
fcd06adc8e
Circling back to a leftover bit from PR39859: https://bugs.llvm.org/show_bug.cgi?id=39859#c1 ...we have this counter-intuitive (based on the test diffs) opportunity to use 'psubus'. This appears to be the better perf option for both Haswell and Jaguar based on llvm-mca. We already do this transform for the SETULT predicate, so this makes the code more symmetrical too. If we have pminub/pminuw, we prefer those, so this should not affect anything but pre-SSE4.1 subtargets. $ cat before.s movdqa -16(%rip), %xmm2 ## xmm2 = [32768,32768,32768,32768,32768,32768,32768,32768] pxor %xmm0, %xmm2 pcmpgtw -32(%rip), %xmm2 ## xmm2 = [255,255,255,255,255,255,255,255] pand %xmm2, %xmm0 pandn %xmm1, %xmm2 por %xmm2, %xmm0 $ cat after.s movdqa -16(%rip), %xmm2 ## xmm2 = [256,256,256,256,256,256,256,256] psubusw %xmm0, %xmm2 pxor %xmm3, %xmm3 pcmpeqw %xmm2, %xmm3 pand %xmm3, %xmm0 pandn %xmm1, %xmm3 por %xmm3, %xmm0 $ llvm-mca before.s -mcpu=haswell Iterations: 100 Instructions: 600 Total Cycles: 909 Total uOps: 700 Dispatch Width: 4 uOps Per Cycle: 0.77 IPC: 0.66 Block RThroughput: 1.8 $ llvm-mca after.s -mcpu=haswell Iterations: 100 Instructions: 700 Total Cycles: 409 Total uOps: 700 Dispatch Width: 4 uOps Per Cycle: 1.71 IPC: 1.71 Block RThroughput: 1.8 Differential Revision: https://reviews.llvm.org/D60838 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@358999 91177308-0d34-0410-b5e6-96231b3b80d8
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