c-rhodes added a comment. In D129476#3643382 <https://reviews.llvm.org/D129476#3643382>, @efriedma wrote:
> Are you saying that it's faster to use clasta targeting a float register, > then move the result to an integer register, rather than use the integer form > directly? Or is the issue just that we want to split the operations in case > we can simplify the resulting bitcast? The former, for the most part. If clast[ab] is inside a loop and is a loop-carried dependency it's considerably faster. If it's a straight bitcast-to-fp + clast[ab] + bitcast-to-int then that costs a cycle or two more depending on the micro-architecture, but in slightly more complicated code from what I've observed the SIMD&FP with bitcasts is as fast as the integer variant, if not faster. > Do we expect SelectionDAG to combine a clasta+bitcast to a single > instruction? Do we have test coverage for that? No, there'll be a mov to an integer register. CHANGES SINCE LAST ACTION https://reviews.llvm.org/D129476/new/ https://reviews.llvm.org/D129476 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
